Take Home PortionDirections Problems (150pts). This part, i.e. th.docx

Take Home Portion
Directions: Problems (150pts). This part, i.e. the Problems
section is ‘open internet’ meaning that you can use any online
source, physical book, slides from class, or personal notes on
the take home portion. Doing so will result in a significant
grade penalty (an F for the course). I will be employing a
number of cheat detection mechanisms to ensure compliance.
You must submit all of your answers as typed text in-line in this
test document. Graphs may be hand-drawn and scanned in or
created digitally.Problems [___/150]
1. (90pts) you are a security analyst that is consulting with an
industrial factory called Fictional Terrible Company (FTC) that
makes a special type of chemical called
“Destructoviralbacteriumuraniumpostapocalypseicus” (DVBUP
for short). FTC is regulated by the Environmental Protection
Agency (EPA) and has to pay for each violation they have:
The EPA provides the following information about penalties:
Laws and regulations
Fine for each violation (per day per incident)
Hazardous Waste Disposal
$71,264
Clean Air Act
$95,284
Clean Water Act
$52,414
Safe Drinking Water Act
$54,789
FTC provides the following information about their industrial
plant
Below is the table of the past problems we have had.
Problem
Incidents

Avg. Number of Days to mitigate
Sabotage Pipe breakages that have led to DVBUP release
16 times in the past 8 years
2
Insecure SCADA system that has led to DVBUP release
2 times in the past 8 years
15
FTC also states the following:
· 8 of the pipe breakages caused a Clean Air Act violation, 4
caused a Clean Water Act violation, and 4 lead to violations of
both the Clean Air and Clean Water acts
· 1 of the times, when hackers breached our SCADA systems,
they released materials into the air, the other led to a release
that went into the water, but also got into the drinking water
table causing us to pay penalties for the both the clean water act
and the safe drinking water act
· We’ve not had any Hazardous Waste Disposal issues
a) (35pts) State the two security problems as threats
quantitatively using Expected Threat Impact (ETI) and Annual
Threat Loss Expectancy (ATLE). Show all of the work.
b) (35pts) Given your calculations in a) you confer with Bill
Mahoney of the UNO Cybersecurity department to come up with
a secure SCADA architecture. Bill says that, for $600,000 he
can assemble a team of students at UNO that can mitigate the

problem. Based on a look at the national numbers, you figure
the solution will reduce the number of exploitations to once in
10 years – but wont change how long it takes to mitigate. You
also confer with a physical security company to look into new
fencing that will reduce the sabotage incident frequency by 90%
(i.e. to once every 5 years). The fencing will cost $500,000.
Draw a single decision tree that shows ALL of the different
options available. Use the information above to estimate the
probabilities and costs at each step.
c) (20pts) Assuming a risk neutral approach, is it cheaper to
mitigate one SCADA, sabotage, both problems, or to do nothing
in a 1 year time interval? What about a 5 year time interval?
Use the decision tree to justify your answer
2. (60pts) You are given the following policy from the NIST SP
800-53.
IA-3: DEVICE IDENTIFICATION AND AUTHENTICATION
The information system uniquely identifies and authenticates

[Assignment: organization-defined specific and/or types of
devices] before establishing a [Selection (one or more): local;
remote; network] connection.
Assume the organization in question – FTC from question 1, has
instantiated the policy using the following selections as follows.
The information system uniquely identifies and authenticates
mobile phones and IoT devices before establishing a network
connection.
a) (35pts) Write a first order logic statement that represents the
control for FTC.
b) (15pts) Identify a non-compliant state (i.e. scenario that is
not acceptable by the policy) using first order logic.
c) (10pts) Given your answers, draw a Venn diagram that
visibly shows the “secure states” and “insecure states” for the
information system. Assume a closed-world assumption is in
place (i.e. only your logic statement defines what is secure and
insecure.

Anim. Behav., 1983, 31, 748-758
TRANSFER OF INFORMATION CONCERNING DISTANT
FOODS:
A LABORATORY INVESTIGATION OF THE
'INFORMATION-CENTRE' HYPOTHESIS
BY BENNEIT G. GALEF, JR & STEPHEN W. WIGMORE
Department of Psychology, McMaster University, Hamilton,
Ontario, L8S 4Kl Canada
Abstract. When choosing between two novel diets, an 'observer'
rat (Rattus norvegicus) prefers that diet
previously eaten by a 'demonstrator' conspecific with whom the
observer has interacted prior to making
its choice between diets. Demonstrator influence on observer
diet selection is maintained even if, during
the period of demonstrator-observer interaction, the
demonstrator is anaesthetized and a wire-mesh
barrier prevents the demonstrator from physically contacting the
observer. Demonstrator influence on
observer diet choice is blocked by either rendering the observer
anosmic or placing a transparent
Plexiglas barrier between demonstrator and observer during
their period of interaction. We conclude

that olfactory cues passing from demonstrator to observer
provide observers with information con-
cerning demonstrators' diets and that these olfactory cues are
sufficient to bias diet selection by ob-
servers. Further, observer rats that hav~ learned the locations at
which each of three diets are inter-
mittently available can use information provided by
demonstrators to increase foraging efficiency. We
discuss the implications of the results both for the 'information-
centre' hypothesis of the function of
mammalian aggregations and for previous studies of social
transmission of diet preference in rats.
Wild Norway rats (R. norvegicus) are social,
central-place foragers. Each rat lives as a
member of a colony inhabiting a fixed system
of burrows from which colony members emerge
to forage and to which they subsequently return
(Calhoun 1962; Telle 1966).
It has been suggested that in environments
characterized by an unpredictable and patchy
distribution of food, social birds or mammals
which forage from a central place could benefit
from exchange of information with conspecifics
at the central site concerning the availablility
of food in the larger environment (Ward &
Zahavi 1973; Erwin 1977; Bertram 1978 ;
Waltz 1982). This 'information-centre' hypothe-
sis concerning the function of vertebrate aggre-
gations carries the implication that members of
vertebrate social groups can acquire information
from others of their species concerning potential
feeding sites or foods remote in both time and
space from the locus of information trans-
mission (Ward & Zahavi 1973; De Groot 1980).

Although the hypothesis that aggregation
sites of birds and mammals may serve as
information-centres is an attractive one, evi-
dence sufficient to establish such a function of
sociality in vertebrates has proven difficult to
collect in field situations. Supporting evidence is
largely circumstantial or comparative rather
than direct (De Groot 1980). Further, there is
little evidence from laboratory study of either
mammals or birds of behavioural mechanisms
sufficient to support the transmission from one
individual to another of information concerning
distant food sources. In the literature, it is
usually assumed that unsuccessful vertebrate
foragers can use behavioural cues to identify
successful foragers at a central site such as a
burrow or roost, and will then follow a successful
individual to food (Ward 1965; Ward & Zahavi
1973; De Groot 1980; Waltz 1982).
It is, of course, possible that information about
distant foods can be transferred via behavioural
mechanisms other than following to a food
source (von Frisch 1967). For example, results
of previous studies in our laboratory indicate
that flavour cues contained in the milk of a
lactating rat reflect the flavour of her diet. These
flavours in mother's milk are sufficient to en-
able pups nursing from a dam to recognize her
diet at weaning and to cause pups to seek their
mother's diet when initiating feeding outside
the nest (Galef & Clark 1972; Galef & Henderson
1972; Galef & Sherry 1973). Thus the nest-site
serves as an information-centre for weanling

rat pups where they acquire information about
foods distant in both time and space. Such an
information-centre is a restricted one in that
the medium for information transfer (mother's
milk) is available only to lactating females and
the information contained in the medium can
only be received by suckling young.
There is also evidence suggesting that adult
rats might be able to exchange information
748
IIbl
2 Ooys 1 Doy 15 Min TEST
[E!NIA.-- ---.. ~0, ~' lot.
STEP 1 STEP 2 STEP 3 STEP 4 STEP 5
GALEF & WIGMORE: INFORMATION TRANSFER IN RATS
concerning distant foods. Strupp (1982) has
shown that an observer rat, choosing between
two diets available to a demonstrator on the
opposite side of a wire-mesh barrier from the
observer, will exhibit a strong preference for
whichever diet the demonstrator is eating
(see also Posadas-Andrews & Roper 1983).
While Strupp's findings indicate that adult rats
can exchange information concerning their
diets, her paradigm allowed demonstrator and
observer to interact in the presence of the foods
about which information was being communi-

cated. Extensive modifications in Strupp's
procedure were, therefore, necessary to explore
the possibility that rats can exchange informa-
tion concerning foods distant from an ingestion
site.
In the series of laboratory experiments des-
cribed below, we first demonstrate that one
Norway rat can communicate to another infor-
mation concerning food it has eaten at a distant
site. Second, we determine the mode of trans-
mission of this information, and finally we
demonstrate that the transmitted information
is adequate to facilitate foraging by its recipient.
Experiment 1
The first experiment was undertaken to deter-
mine whether one adult rat (a 'demonstrator')
cim communicate information to a second (an
'observer') concerning the food the demon-
strator has eaten prior to interaction with the
observer. Although we will refer to the rats in
our experiments as demonstrators and obser-
vers to conform to current usuage (Levitsky &
Strupp 1981; Strupp 1982), we do not intend to
imply that the behavioural process supporting
information transfer is learning by observation.
In fact, our experiments will demonstrate that
observational learning is not involved.
Methods
Subjects. Subjects were 32 Long-Evans rats
born in the McMaster colony to breeding pairs
descended from animals purchased from Blue
Spruce Farms (Altamont, N.Y.). Prior to

initiation of the experiment all subjects were
maintained ad libitum on Purina Laboratory
chow and water in same-sex groups of 4 to 5
littermates.
Sixteen subjects, 42 days of age at the time
of initiation of the experiment, served as
observers. Sixteen 90-120-day-old subjects
served as demonstrators. At the start of the
749
experiment, each observer was randomly paired
with a demonstrator of the same sex.
Apparatus. During the experiment, subjects
were housed and tested as demonstrator-
observer pairs in 42.5 x 24 x 27.5-cm wire-
mesh hanging cages (Wahmann Co., Balitmore,
Md). Each hanging cage was divided in two
equal parts by a 1.25-cm (t-inch) wire-mesh
partition (24 x 27.5 em) attached at the mid-
points of each cage's 42.5-cm sides. The same
apparatus was also used in experiments 2-5.
Procedure. Our procedure was designed to
mimic a situation in which a foraging rat ingests
a food at some distance from the burrow, re-
turns to the burrow, and interacts with a fami-
liar burrow-mate. We were interested to know
whether, as a result of such interaction, the
burrow-mate could acquire information concern-
ing the food the forager had eaten and would
use this information in selecting a diet.
Treatment of subjects during the ~xperiment

was as follows (Fig. la): Step 1: demonstrator
and observer were first maintained together
with ad libitum access to Purina Laboratory
Chow pellets for a 2-day familiarization period.
Step 2: the demonstrator was moved to the oppo-
site side of the wire-mesh partition from the ob-
server and food-deprived for 24 h to ensure
that the demonstrator fed when given the op-
portunity to do so. Step 3: chow was then
removed from the observer's side of the cage
(in preparation for testing) and the demonstrator
was moved to an enclosure in a separate room
and allowed to feed for 30 min on either pow-
dered Purina Laboratory chow adulterated
with 2 % by weight Hershey's cocoa (cocoa-
n.,
2 Doy. 1 Doy
[1)-
Fig. 1. Schematic diagram of the procedures of experi.
ments 1 and 2 (Fig. 1a) and experiments 3, 4 and 5 (Fig.
1b).O = observer;D = demonstrator; hatching indicates
that pellets of Purina Laboratory chow were present in
the cage.
Mingwen
Pencil
Mingwen
Pencil
Mingwen
Pencil

750 ANIMAL BEHA VIOUR, 31, 3
flavoured diet) or powdered Purina Laboratory
chow adulterated with 1% by weight Mc-
Cormick's pure ground cinnamon (cinnamon-
flavoured diet). Step 4: the demonstrator was
returned to the observer's cage and demon-
strator and observer were allowed to interact
for 15 min. Step 5: the demonstrator was re-
moved from the experiment and the observer
was offered, for 60 h, two weighed food-cups,
one containing cinnamon-flavoured diet and
one containing cocoa-flavoured diet. The food
bowl containing the diet which a given ob-
server's demonstrator had eaten was placed in
the front of the cage of half the observers and
in the back of the cage of the remainder of
observers.
The experimenter weighed the two food cups
once every 12 h throughout the 6O-h test period.
Results and Discussion
The results of experiment 1 are presented in
Fig. 2, which shows the mean amount of cocoa-
flavoured diet, as a percentage of total amount
eaten, ingested by observers whose demonstrators
had eaten cocoa-flavoured or cinnamon-
flavoured diet during step 4 of the experiment
(see Fig. la). Those observers whose demon-
strators ate cocoa-flavoured diet ~te a greater
0-12h 48-60h

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DEMONSTRATORS' DIET

Fig. 2. Mean amount of cocoa-flavoured diet ingested, as
a percentage of total amount eaten, by observers whose
demonstrators had eaten either cocoa- or cinnamon-
flavoured diet. eo = cocoa-flavoured diet; eIN =
cinnamon-flavoured diet. Bars indicate::!: ISE.
percentage of cocoa-flavoured diet than did
those observers whose demonstrators ate
cinnamon-flavoured diet (0-12-h test, Mann-
Whitney U = 0, P < 0.(01). The effects of the
diet eaten by the demonstrator on the diet
preference of the observer were still observable
48-60 h after the interaction of observer and
demonstrator in step 4 of Fig. la (Mann-
Whitney U = 2, P < 0.001).
The results of experiment I clearly demon-
strate that rats are able to communicate infor-
mation concerning a diet they have eaten at a
time and place distant from the locus of their
interaction. The data also show that this
information is sufficient to bias a recipient's
subsequent choice of diet.
Experiment 2
In experiment 1, an observer and demonstrator
interacted immediately after the demonstrator
had eaten a novel diet and the observer had the
opportunity to choose between novel diets
immediately following receipt of information
from the demonstrator. Free-living rats must
expend time in returning from a feeding site to
their home burrow, and foragers departing from
their home burrow must expend further time in
reaching a feeding site. If the capacity of rats

to transmit information concerning a food they
have eaten at a distance from the nest site is to
function as the basis for information transfer at
the home-site in natural settings, transmission
must occur even if there is a delay between a
successful forager's ingestion of a food and
its return to the burrow and a further delay bet-
ween the interaction of a successful forager with
other rats and the latters' arrival at a potential
feeding site. The present experiment was under-
taken to discover whether the information
transfer demonstrated in experiment 1 could
tolerate such delays.
Methods
Subjects. Forty-eight 42-day-old experi-
mentally-naive Long-Evans rats born in the
McMaster colony served as observers, and 48
120-day-old Long-Evans rats as demonstrators.
Observers and demonstrators were randomly
assigned to one of three conditions: Control,
30-min-delay and 60-min-delay (described
below).
Apparatus. The apparatus was that used in
experiment 1.
Procedure. The eight demonstrator and eight
observer rats assigned to the Control condition
Mingwen
Pencil
Mingwen

Pencil
were treated identically to observers and demon-
strators in experiment I (see Fig. la). Demon-
strators and observers assigned to 30-min-delay
and 60-min-delay conditions were treated
identically to those in the Control condition
except in the following two respects. (I) After
each demonstrator had eaten either cinnamon-
flavoured or cocoa-flavoured diet for 30 min
(step 3 of Fig. la), it was food-deprived for
either 30 min (30-min-delay condition) or 60
min (60-min-delay condition) before being
placed in the cage with its observer (step 4 in
Fig. I a). (2) After the observer and demon-
strator had interacted for 15 min (step 4 in
Fig. la), the observer was food-deprived for
either 30 min (30-min-delay condition) or 60
min (60-min-delay condition) before being
offered a choice of cinnamon- and cocoa-
flavoured diets. A third departure from the
procedure of experiment I was that the food
cups offered to observers in the test phase
(step 5) were weighed only once, 12 h after the
initiation of testing.
The main results of experiment 2 are pre-
sented in Fig. 3, which shows the mean
percentage of cocoa-flavoured diet ingested by
observers whose demonstrators had eaten either
cinnamon- or cocoa-flavoured diet. Observers

in both Control and 30-min-delay conditions
exhibited marked effects of interaction with
demonstrators on their food choice (Mann-
3O-DELAY-30 6O-OEI.AY-60
80
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8
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30-
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co a.Io
DEMONSTRATORS' DIET
a percentage of total amount eaten by observers in
Control, 30-min-delay, and 6O-min-delay groups when
their demonstrators had eaten either cinnamon- or cocoa-
flavoured diet. Bars indicate :f: 1 SE.

1S1
Whitney U; Control condition, U = 4, P =
0.002, 30-min-delay condition, U = 3, P =
0.002). There was a marginal effect of demon-
strator diet on the diet selection of observers in
the 6O-min-delay condition, but this failed to
reach significance (Mann-Whitney U = 14,
P < 0.064).
The results of the present experiment repli-
cate the finding in experiment 1 of a transfer of
information between adult rats concerning a
diet distant in time and space. The results also
indicate that this transfer is not disrupted by
30-min delays between a demonstrator's feed-
ing and its interaction with an observer and an
observer's interaction with a demonstrator and
that observer's initiation of feeding. The data
further suggest that similar I-h delays interfere
with the influence of demonstrators on the
observers' diet choice. The present results do
not provide sufficient information to determine
whether this decrement is due to the first I-h
delay causing a deterioration of the signal pass-
ing from demonstrator to observer, or the
second I-h delay reducing the eft'ect of the signal
on the observer's behaviour. We shall address
this issue elsewhere.
Experiment 3
Experiments 3, 4, and 5 were undertaken to
determine the medium of transmission of
information from demonstrator to observer.

Methods
Subjects. Thirty-two experimentally-naive
42-day-old Long-Evans rats born in the Mc-
Master colony served as observers and 32
90-11O-day-old Long-Evans rats served as
demonstrators. Observers and demonstrators
were randomly assigned to the two experimental
groups described below.
Apparatus. The apparatus was the same as
used in experiment I.
.
Procedure. The procedure was similar to
that described in Methods of experiment 1,
except that during the period of interaction bet-
ween demonstrator and observer in step 4 of
Fig. la, demonstrator and observer were sepa-
rated by a partition. For subjects in the 'Screen
condition' this partition was constructed of
1.3-cm (t-inch) wire-mesh. For subjects in the
'Plexiglas condition' this partition was con-
structed of clear, 0.65-cm (i-inch) Plexiglas.
Figure 1b presents a schematic diagram of the
procedure of the present experiment. Minor
differences between the procedure of experiment
100
SCREEN
90

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751 ANIMAL BEIiA VI OUR, 31, 3
I and that of the present experiment may be
noted in comparison of Fig. la and lb. These

differences are of no particular moment. They
were introduced to ascertain whether the
phenomenon under examination was sufficiently
robust to withstand small modifications in
procedure.
sented in Fig. 4, which shows the mean amount
of cocoa-flavoured diet, as a percentage of
total amount eaten, ingested by observers in
Screen and Plexiglas conditions whose demon-
strators had eaten either cocoa- or cinnamon-
flavoured diet. Observers in the Screen condition
exhibited an influence of their respective
demonstrators on their diet choice, while
subjects in the Plexiglas condition did not
(Mann-Whitney U; Screen condition, U = 0,
P = 0.001; Plexiglas condition, U = 30, P>
0.30).
The results of the present experiment indi-
cate that transfer of information from demon-
PLEXIGLAS
8 8
CO CIN
DEMONSTRATORS' DIET
a percentage of total amount eaten, by observers in
Screen and Plexiglas conditions when their demonstrators

had eaten either cinnamon- or cocoa-flavoured diet. Bars
indicate :J: 1 SE.
strator to observer can occur in the absence of
free interaction between pair members. The
data further indicate both that visual contact
between observer and demonstrator is not
sufficient and that some other form of contact
(olfactory, gustatory, or tactile) is necessary for
information transfer.
Experiment 4
In this experiment we examined whether ol-
factory cues were sufficient to effect information
transfer from demonstrator to observer.
Methods
Subjects. Forty Long-Evans rats, 42 days of
age at the initiation of the experiment, served
as observers, and 40 lOO-l20-day old rats of
the same strain served as demonstrators. Half
of the observers and half of the demonstrators
were randomly assigned to Control and Anaes-
thetized conditions.
used in experiment 1.
Procedure. Subjects in the Control group of
the present experiment were treated identically
to those in the 'Screen' condition of experiment
2 (see Methods of experiment 2 and Fig. Ib).
Subjects in the Anaesthetized condition were
treated like those in the Control group except
that immediately after each demonstrator had

eaten cinnamon- or cocoa-flavoured diet in
step 3, it was anaesthetized by intraperitoneal
injection of sodium pentobarbitol, draped over
an inverted Pyrex petri dish (100 em diam x
50 em), fastened to it with a piece of masking
tape, and placed in the apparatus facing its
observer with the end of its nose 2.5 em from the
wire-mesh partition separating demonstrator
and observer. (Pilot studies had revealed that
an anaesthetized demonstrator 2.5 em from a
hardware cloth partition could not be physically
contacted by an observer on the far side of the
barrier.) Each anaesthetized demonstrator was
left on its side of the cage for 15 min (cf. step
4, Fig. Ib) and then removed. Each observer
was then offered a choice of cinnamon- and
cocoa-flavoured diets for 12 h.
Results
sented in Fig. 5, which shows the mean per-
centage of cocoa-flavoured diet ingested by
observers in Anaesthetized and Control groups
when their demonstrators had eaten either
cinnamon- or cocoa-flavoured diet. Observers
CONTROL ANAESnETlZED
T
10

o
10 10
CO CIN
10
CO
DEMONSTRATORS' DIET
a percentage of total amount eaten, by observers in
Anaesthetized and Control groups when their demonstra-
tors had eaten either cinnamon- or cocoa-flavoured diet.
Bars indicate :f: 1 SE.
in both Anaesthetized and Control groups
exhibited marked effects of interaction with
demonstrators on their food choice (Mann-
Whitney U; Anaesthetized group, U = 8, P <
0.002; Control group, U = 13, P < 0.02).
'
Discussion .
Because transfer of information between
demonstrator and observer occurred in the
absence of physical contact between them, it
can be concluded that gustatory cues passing
from demonstrator to receiver (for example the
taste of the demonstrator's saliva or of food
particles clinging to the demonstrator's coat)
are not necessary for information transfer to

occur. The finding that demonstrators kept
2.5 em distant from their observers can transmit
the necessary signal suggests that olfactory cues
passing from demonstrator to observer are
sufficient to support the transmission process.
Because anaesthetized demonstrators are as
effective in transmitting information as intact
demonstrators, it would appear that signal emis-
sion by the demonstrator is a passive rather
753
than active process, and that the necessary
signal is emitted by the demonstrator rather
than elicited by the observer.
Experiment 5
Given that physical contact . between demon-
strator and observer is not necessary for informa-
tion transfer from the former to the latter, it
seems probable that olfactory cues sent by the
demonstrator and received by the observer are
sufficient for communication to occur. If so,
anosmic observers should not exhibit an influ-
ence of interaction with an observer on their diet
choice.
~ethods .
Subjects. Thirty-six 42-day-old Long-Evans
rats served as observers and 36 90-day-old
rats of the same strain served as demonstrators.
Half the observers were randomly assigned to an
Anosmic group and half to a Control group.

used in experiment I.
Procedure. The procedure was that of experi-
ment 2 (see Fig. Ib) except in two respects.
(1) Twenty-four hours following initiation of the
experiment, at the start of the last day of
familiariZJltion, observers assigned to the Anos-
mic group were rendered anosmic by intranasal
lavage with zinc sulphate solution (Alberts &
Galef 1971). Observers in the Control group
were treated with isotonic saline solution at
the time subjects in the Anosmic group were
treated with Zinc Sulphate. (2) For 30 min during
step 3 of Fig. Ib, demonstrator rats were fed
either unadulterated powdered Purina Labora-
tory Chow (Pu Diet) or Normal Protein Test
Diet (NPT Diet) (Teklad Test Diets, Madison,
Wise.). NPT Diet is a powdered mixture of the
following ingredients (values in g{kg): vitamin-
free test casein, 260.06; corn starch, 598.24,
hydrogenerated vegetable oil, 80.00; cod-liver
oil, 20.00, USP XIV Mineral mix 40.00; vita-
mins, 1.70. (3) Observers were offered a choice
between Pu Diet and NPT Diet for 12 h during
the test period (step 5 of Fig. 1b).
The change in diets offered to demonstrators
and observers in the present experiment was
necessitated by pilot studies showing that
anosmic rats could not discriminate cinnamon-
from cocoa-flavoured
.
diet. (To test for the

ability of anosmic subjects to discriminate bet-
ween any pair of diets we compared the ability
of anosmic 'and saline-Iavaged subjects to
exhibit a toxicosis-induced aversion toone of
CONTROL ANOSMIC
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754 ANIMAL BEHAVIOUR, 31, 3
those two diets when subsequently offered both
simultaneously. The results of such tests were
clear-cut. Anosmic subjects poisoned after they
had eaten cocoa-flavoured diet ate as much
cocoa- as cinnamon-flavoured diet in a 6-h test
conducted 24 h after poisoning; control subjects
poisoned after they had eaten cocoa-flavoured
diet ate no cocoa-flavoured diet during the test.
Both anosmic and control subjects poisoned
after ingesting NPT Diet ate no NPT Diet when,
24 h after poisoning, they were offered a choice
of NPT and Pu Diets for 6 h.) If anosmic obser-
vers were unable to discriminate between the
two diets offered during testing (step 5 of Fig.
1b), then even if we were to observe a breakdown
in demonstrator influence on diet selection in
anosmic observers, we could not attribute this
deficit to an anosmia-induced interference with
communication between demonstrator and
observer.
The main results of experiment 5 are presented

in Fig. 6, which shows the mean amount of
60
30
NPT PU
'
NPT PU
"DEMONSTRATORS' DIET
Fig. 6. Mean amount of NPT Diet, as a percentage of
total amount eaten, ingested by observers in Anosmic and
Control 'groups when their demonstrators had eaten
either NPT Diet or Pu Diet. Pu = powdered Purina
Laboratory Chow, NPT = Normal Protein Test Diet.
Bars indicate :l: 1 SE.
NPT Diet, as a percentage of total amount
eaten, ingested by observers in Anosmic and
Control groups whose demonstrators had eaten
either NPT Diet or Pu Diet. Observers in the
Control group whose demonstrators ate NPT
Diet ate significantly more NPT Diet during
testing than did observers in the Control group
whose demonstrators ate Pu Diet (Mann-
Whitney U = 4, P < 0.002). By contrast, the
demonstrators' diet did not affect diet choice
by anosmic observers during testing (Mann-
Whitney U = 35, P > 0.30).
Given that NPT and Pu Diets are discrimin-
able by anosmic subjects and that demonstrators
can successfully transfer information concerning

NPT and Pu Diets to intact observers, the
failure of anosmic observers to use the informa-
tion transmitted by their observers suggests
that anosmia interfered with receipt of the
necessary olfactory information. The results of
both the present experiment and experiment 4
thus indicate that the cue passing from demon-
strator to observer is olfactory in nature.
We have independent evidence of the pre-
sence of an olfactory cue carried on the breath
of rats and reflecting the flavour of their diets,
which could serve as the means of information
transfer from demonstrator to observer. A
human subject (C.M.), by sniffing rat breaths,
successfully distinguished six rats fed cinnamon-
flavoured diet from six rats fed cocoa-
flavoured diet with better than 85 % accuracy
during two 18-trial sessions (binomial test,
Session 1, x = 3, P < 0.004, Session 2, x =
2, P < 0.00 I). While this does not prove that
observer rats use information carried 011 the
breath of demonstrators in selecting diets in
our experiments, it does indicate that such
information would be sufficient for communi-
cation from demonstrator to observer.
Experiment 6
The results of the experiments described above
demonstrate that rats can communicate informa-
tion to their fellows about diets they have
ingested far from the locus of information
transfer. The data also indicate that such infor-
mation can effect food preferences in a receiver,
and that the signal passing from demonstrator
to observer is olfactory in nature. They do not

however provide evidence that such information
can be used by a recipient to facilitate foraging
in environments characterized by an unpredic-
table and patchy distribution of food.
I FOOO CUP
~ONE-WAY DOOO
I REMOVABlE DOOO
HARDWARE ClOTH
In the present study we simulated an environ-
ment in which each of a variety of foods became
available in fixed locations on an unpredictable
schedule. Once our subjects had demonstrated
that they knew the location in which each food
was to be found, we provided each subject with
the opportunity to interact with a conspecific
which had eaten one of the foods. We then
determined whether our subjects would use the
information provided by the fed individual to
direct their subsequent foraging.
Methods
Subjects. Eight Long-Evans rats 42 days of
age at the start of experimentation served as
subjects and eight additional rats of the same
age served as demonstrators. One subject and
one demonstrator were excluded from the
experiment when the subject learned to open

the one-way doors described below from both
sides.
Apparatus. The apparatus is illustrated in
plan view in Fig. 7. It consisted of a three-arm
maze attached to a cage holding four subject-
CH DIET
CO DIET
CIN DET CHOICE POINT
Fig. 7. Plan of apparatus used in experiment 6. CH =
cheese-flavoured; CIN = cinnamon-flavoured; CO =
cocoa-flavoured; S = Subject; D = Demonstrator.
755
demonstrator pairs. Each I x O.09-m arm of
the maze (constructed of plywood with a
transparent Plexiglas cover) led via a removable
guillotine door to a 23 x 15-cm goal box con-
taining a food cup. At the choice point of the
maze the subject was faced with a choice bet-
ween three ont:-way doors.
Each subject was maintained in a 30 x 30 x
l5-cm plywood cage opening into an alley via a
removable guillotine door. Each subject was
housed adjacent to its demonstrator and sepa-
rated from the latter by a 30 x 15-cm wire-
mesh partition.
Procedure. To begin the experiment, subjects
and demonstrators were tail-marked for indivi-

dual recognition, introduced individually into
their respective compartments, and placed on a
23 h/day food-deprivation schedule.
Habituation. Three days following initiation
of the experiment, the guillotine doors were
removed from the subjects' cages and from the
goal boxes, the one-way doors were taped open,
and subjects were allowed to explore around the
apparatus for 2 h/day. Three different diets,
cinnamon-flavoured powdered Purina Labora-
tory chow (Diet CIN), cocoa:-flavoured pow-
dered Purina Laboratory chow (Diet CO) and
cheese-flavoured powdered Purina Laboratory
chow (Diet CH, 2 % by weight Kraft's romano
cheese) were placed in the goal-boxes in the
positions indicated in Fig. 7. These apparatus
habituation sessions were continued for several
days, with the experimenter gradually lowering
the flaps on the one-way doors from one day
to the next, until the one-way doors were
completely closed and all subjects were passing
through them without hesitation.
Training. On training days, each subject
received four trials per day. To begin a series
of trials the experimenter consulted a random
number table to determine which of the three
goal-boxes would be open to the first subject.
That goal-box door was opened, the door to the
first subject's living cage removed, and the
subject was given 5 min to pass through a
one-way door. If the subject chose the one-way
door leading to food it was allowed to feed for
2 min and then returned- to its living cage. If
the subject chose one of the other two one-way

doors, it was left in the arm it had chosen for
2.5 min and then returned to its living cage. If
the subject failed to pass through a one-way
door within 5 min, it was returned to its living
cage.
"f
. SUBJECT 1. SLeJECT 2
"
SUBJECT3
I .. SUBJECT4
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Any subject choosing either of the incorrect
doors was left in its living cage for 2 min and
then allowed to choose again. The first trial was
repeated until the subject chose the correct one-
way door.
After the first subject's first trial of a day was
completed, the second, third and fourth subjects'
first trials of that day were run in an identical
fashion to the first trial of the first subject, ex-
cept that the goal-box door that was opened for
each subject was different from that opened
for the preceding subject.
Second, third and fourth trials on each day
for each subject were run under conditions
identical to those prevailing on that subject's
first trial of the day. Because the location of
the three diets remained fixed and the same goal-
box was open on trials 1--4of each day for each
subject, perfect performance was possible on
trials 2--4 (but not trial 1) of each day. After
all subjects had completed their four trials, each
was offered a food bowl containing unadult-
erated powdered Purina Laboratory chow for
1 h.
Testing. Once subjects were responding cor-
rectly on an average of two or more of the
last three trials of each day for six consecutive
days, that subject entered into the test phase of
the experiment. During the test phase, each
subject was run 4 trials/day, exactly as during

training. However, during testing, 45 min prior
to each subject's first trial of each day, that
subject's demonstrator was removed from its
living cage, and treated in the following fashion:
(1) Each demonstrator was first placed in a
cage in a separate room and allowed to feed
for 30 min on the diet which was located in the
arm of the maze to which that demonstrator's
subject was to have access on that day. (2)
The demonstrator was then returned to its
living cage to interact through the wire-mesh
partition with its subject for IS min, and was
then removed from its living cage until that
day's ; testing of all subjects was completed.
Each subject was tested (four trials/day) for 12
consecutive days.
. The main results of .experiment 6 are pre-
sented in Fig. 8, which indicates the percentage
correct responses made by each of the seven
subjects on its daily first trials of the last 18
days of training and on its daily first trials
during the 12 days of testing. Four of the seven
subjects did significantly better than chance
during the testing phase of the experiment
(Binomial test, Ho that p = !; see Fig. 8 for
significance levels). It is somewhat disappoint-
ing that not all subjects made use of the informa-
tion provided by their respective demonstrators
in selecting an arm of the maze for initial
exploration. However, the fact that four subjects
did use the information provided by their
demonstrators indicates that the mode of

information transfer examined in experiments
1-5 is adequate to facilitate foraging in
circumstances in which a food is available
intermittently at a fixed location.
General Discussion
The results of the present experiments demon-
strate that adult rats can exchange information
concerning ingested foods at a time and place
distant from the ingestion site. The results also
demonstrate that the reception of olfactory
information from conspecifics can profoundly
bias diet choice in the recipient, and under
appropriate circumstances, can facilitate the
recipient's location of available nutrients. The
present data thus provide indirect support for
30
"
01 I
LAST 18 DAYS
OF TRAINING
I
12 DAYS
OF TESTING
Fig. 8. Percentage of correct choi~ on first trials by
individual subjects on the last 18 days of training anQ the
12 days of testing in experiment 6.

Galef, B. G., Jr. & Clark, M. M. 1971b. Parent-offspring
interactions determine time and place of first
ingestion of solid food by wild rat pups. Psychon.
Sci., 25, 15-16.
Galef, B. G., Jr. & Clark, M. M. 1972. Mother's milk and
adult presence: two factors determining initial
dietary selection by weanling rats. J. compo physiol.
Psychol., 78, 220-225.
Galef, B. G., Jr. & Heiber, L. 1976. The role of residual
olfactory cues in the determination of feeding site
selection and exploration patterns of domestic rats.
J. compo physiol. Psychol., 90, 727-739.
Galef, B. G., Jr. & Henderson, P. W. 1972. Mother's milk:
A determinant of the feeding preferences of wean-
ing rat pups. J. compo physiol. Psychol., 78,
213-219.
Galef, B. G., Jr. & Sherry, D. F. 1973. Mother's milk: A
medium for the transmission of cues reflecting the
flavor of mother's diet. J. compo physiol. Psychol.,
83, 374-378.
Levitsky, D. A. & Strupp, B. J. 1981. Malnutrition and
tests of brain function. In: Nutrition and Behavior
(Ed. by A. A. Miller), Philadelphia, Pa: Franklin
Institute Press.
Posadas-Andrews, A. & Roper, T. J. 1983. Social trans-
. mission of food-preferences in adult rats. Anim.
Behav., 31, 265-271.

Strupp, B. J. 1982. Malnutrition and animal models of
cognitive development. Ph.D. thesis, Cornell
University.
Telle, H. J. .1966. Beitrag zur Kenntnis der Verhaltensweise
von Ratten, vergleichend dargestellt bei Rattus
norvegicus und Rattus rattus. Z. Angew. Zool., 53,
129-196. '
von Frisch, K. 1967. The Dance Language and Orientatioll
of Bees. Cambridge, Mass.: Belknap Press.
Waltz, E. C. 1982. Resource characteristics and the evo-
lution of information centers. Am. Nat., 119, 73-90.
Ward, P. 1965. Feeding ecology of the Black-faced Dioch
(Quelea quelea) in Nigeria. Ibis, 107, 173-214.
Ward, P. & Zahavi, A. 1973. The importance of certain
assemblages of birds as "information-centres" for
food-finding. Ibis, 115, 517-534.
(Received 14 September 1982; revised 28 October 1982;
MS. number: A3031)
.Journal of Comparative Psychology
198:3, Vol. 97, No.4, :358-:36:3
Copyright 198:1 hy the
American Psychological Association, Inc.

A Failure to Find Socially Mediated Taste Aversion
Learning in Norway Rats (R. norvegicus)
Bennett G. Galef, Jr., Stephen W. Wigmore, and Deborah J.
Kennett
McMaster University, Hamilton, Ontario, Canada
Observer rats interacted with conspecific demonstrators
immediately after
demonstrators ate a novel diet and were made ill by LiCI
injection. Following
their interaction with demonstrators, observers were tested for
aversion to
their ill demonstrator's diet. Previous research has shown that
(a) an observer
can extract information from a demonstrator sufficient to permit
identification
of the demonstrator's diet (Galef & Wigmore, 1983) and (b) a
rat ill from LiCI
toxicosis is an adequate unconditioned stimulus in a taste
aversion learning
paradigm (Lavin, Freise, & Coombes, 1980). Further, two of the
present
experiments demonstrated that cues emitted by a rat, reflecting
the particular
diet it has eaten, are an adequate conditional stimulus in a
toxicosis-induced
aversion learning situation. Observer avoidance of a diet
previously ingested
by an ill demonstrator was, however, not demonstrated. The
implications of
the failure to find socially mediated aversion learning are
discussed.
The results of a number of recent studies
demonstrate that signals emitted by rats

suffering LiCI toxicosis can serve as uncon-
ditioned stimuli in a taste aversion learning
paradigm. A rat ingesting some unfamiliar
diet prior to exposure to a LiCI-injected
conspecific subsequently exhibits reluct-
ance to ingest that diet (Bond, 1982;
Coombes, Revusky, & Lett, 1980; Lavin,
Freise, & Coombes, 1980; Stierhoff &
Lavin, 1982).
Although exposure to an ill conspecific
can result in a specific food avoidance in
rats in laboratory settings, it is not obvious
how such socially mediated taste aversion
learning might be used by free-living ani-
mals to enhance avoidance of toxic foods.
If an unfamiliar food eaten by an individual
prior to interaction with an ill conspecific
were safe, then subsequent avoidance of
that food would be counterproductive. If,
to the contrary, an unfamiliar food ingested
prior to interaction with an ill conspecific
were toxic, then information received from
This research was supported by Natural Sciences
and Engineering Research Council of Canada Grant
A0307 and McMaster University Research Board
grants to B. G. Galef, Jr. We thank Harvey Weingar-
ten and Mertice Clark for their thoughtful commen-
tary on earlier drafts of the manuscript.
Requests for reprints should be sent to Bennett G.
Galef, Jr., Department of Psychology, McMaster Uni-
versity, Hamilton, Ontario, Canada L8S 4Kl.
the ill individual would be redundant. Even

in the absence of social learning, a rat in-
gesting an unfamiliar toxic food would sub-
sequently avoid that food. The functional
significance of the potential of ill rats to
act as unconditioned aversive stimuli in an
avoidance learning situation is not obvious.
Stierhoff and Lavin (1982) suggested
that an ill rat may deposit aversion-produc-
ing residual odors in the vicinity of a nox-
ious food and that such odors might inhibit
ingestion of that food by others of their
colony (see also Steiniger, 1950). Unfortu-
nately, Stierhoff and Lavin did not provide
evidence either that aversion-producing
substances emitted by ill rats directly in-
hibit ingestion or that rats preferentially
deposit such substances in the vicinity of
toxic foods.
The results of recent studies both in our
laboratory and elsewhere demonstrate that
a rat briefly exposed to an unpoisoned con-
specific that has eaten some food subse-
quently exhibits an enhanced preference
for that food. One rat can extract infor-
mation from another concerning the diet
the latter individual has recently eaten
(Galef & Wigmore, 1983; Posadas-Andrews
& Roper, 1983; Strupp & Levitsky, in press-
a, in press-b). This finding, taken together
with the observation that an ill rat can
serve as an unconditioned stimulus for
taste aversion learning, suggests that a rat
358

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360 B. GALEF, JR.,S. WIGMORE, AND D. KENNETT

30-MININTERACTION 2-HRINTERACTION
Step 5 Step5
DEMONSTRATOR'S DIET:
oCocoa
p<.Q02 0 Cinnamon
p<.003
p<.008 p<.001
8 8
SALINE LiCI SALINE LiCI
TREATMENT CONDITION
Figure 2. Mean amount of cocoa-flavoreddiet in-
gested by observers as a percentage of total amount
eaten. (Bars indicate :t 1 SE.)
The main results of Experiment 1 are
presented in Figure 2, which indicates the
mean percentage of cocoa-flavored diet ea-
ten during testing by observers whose dem-
onstrators had eaten either cinnamon-fla-
vored or cocoa-flavored diet. As is evident
from inspection of the figure and as statis-
tical tests confirm (Mann-Whitney U tests,
see Figure 2 for p values), subjects in both
experimental and both control groups ex-

hibited a marked preference for the diet
that their respective demonstrators had ea-
ten. Poisoned demonstrators were as effec-
tive in promoting intake of the diet they
had eaten as were unpoisoned demonstra-
tors.
The failure to find an effect of poisoning
demonstrators on their capacity to transfer
a preference for the diet they have eaten is
open to a variety of intepretations. First, it
is possible that although demonstrators
emit signals specifying both the food they
have eaten and that they have eaten some-
thing toxic, observers fail to associate the
two messages. Difficulties in forming aver-
sions to demonstrator-produced cues, prob-
lems in the temporal patterning of receipt
of the two signals, or problems with the
relative strength of the preference induced
by one signal and the aversion induced by
the other are possible causes of the ob-
served failure of transfer of aversion.
Alternatively, as is the case with all null
outcomes, the failure to demonstrate a
transfer of aversion from poisoned demon-
strators to observers may have been due to
our selecting an inappropriate set of exper-
imental conditions. We were, however,
careful to select parameters of toxicosis
induction in demonstrators and of interac-
tion between demonstrator and observer
previously shown to cause observers to
learn aversions to unfamiliar foods ingested

prior to interaction with a poisoned dem-
onstrator (Bond, 1982; Lavin et aI., 1980).
Further, the procedures we used were
clearly adequate to allow observers to ex-
tract information from demonstrators con-
cerning the diets demonstrators had eaten.
Conditions were thus appropriate for aver-
sion transfer from observer to demonstra-
tor, yet the anticipated outcome was not
observed.
We could continue seeking a set of pa-
rameters that would permit socially me-
diated transfer of aversion, but it is not
obvious what conditions to select. We de-
cided instead to ask whether the informa-
tion extracted by an observer from a dem-
onstrator could serve as the conditional
stimulus in a standard aversion learning
paradigm. It seemed to us that if an ob-
server could not form an aversion to the
food a demonstrator had eaten when that
observer was poisoned directly after inter-
acting with a demonstrator fed a novel food,
then it was unlikely that under any condi-
tions observers would avoid a food eaten by
a demonstrator exhibiting symptoms of
toxicosis.
Experiment 2
In this experiment, observers were first
allowed to interact with demonstrators fed
one of two diets. Each observer was then
poisoned by ip injection of LiCI and sub-
sequently offered a choice between the two

diets fed to demonstrators.
Method
Subjects. Thirty-two 42-day-old experimentally
naive Long-Evans rats from the McMaster colony
ABSENCE OF SOCIALLY MEDIATED TASTE AVERSION
359
made ill following ingestion of a novel food
might provide two potentially useful signals
to a conspecific: (a) a signal containing
information sufficient to permit identifi-
cation of the food that the signal-emitter
has recently eaten and (b) a signal capable
of inducing a learned aversion. Exposure to
these two signals in temporal contiguity
might suffice to produce in their recipient
avoidance of the specific diet recently in-
gested by an ill conspecific.
Experiment 1
Our procedure was designed to mimic a
situation in which one rat (a demonstrator)
departs from its burrow, ingests a novel
toxic food, returns to its burrow, and while
suffering toxicosis, interacts with a burrow-
mate (an observer) which subsequently has
the opportunity to ingest the novel food
previously eaten by the demonstrator. Our
goal was to determine whether such a series
of events would result in avoidance by the

observer of the food the demonstrator had
eaten prior to the onset of toxicosis.
Method
Subjects. Sixty-four experimentally naive Long-
Evans rats born in the McMaster colony to breeding
stock acquired from Blue Spruce Farms (Altamont,
New York) served as observers in the procedure de-
scribed below. Each observer was 42 days of age at the
time of initiation of the experiment. Sixty-four addi-
tionaI92-day-old Long-Evans rats from the McMaster
colony served as demcinstrators.
Apparatus. Subjects were housed and tested in
same-sex demonstrator-observer pairs in 42.5 x 24 x
27.5 cm wire mesh hanging cages (Wahmann Co.,
Baltimore, Maryland). Each cage was divided into two
equal parts by a 1.25-cm ('/2-in.) hardware-cloth screen
attached to the midpoint of each 42.5-cm side.
Procedure. Treatment of subjects during the ex-
periment was as follows (see Figure 1):
Step 1: In order to permit familiarization with
both apparatus and partner, demonstrator and ob-
server were maintained together with ad lib access to
Purina Laboratory Rodent Chow pellets (their normal
maintenance diet) and left undisturbed for 2 days.
Step 2: In order to ensure that the demonstrator
ate when given the opportunity to do so, each dem-
onstrator was moved to the opposite side of the screen
partition from its observer and food deprived for 24
hr.

Step 3: In preparation for testing of each observer,
chow was removed from each observer's side of the
apparatus. Each demonstrator was then moved to an
individual enclosure in a room separate from that
housing the apparatus and allowed to feed for 30 min
on either powdered Purina Laboratory Rodent Chow
adulterated 2% by weight with sifted Hershey's Pure
Cocoa (cocoa-flavored diet) or powdered Purina Lab-
oratory Rodent Chow adulterated 1% by weight with
McCormick's Fancy Ground Cinnamon (cinammon-
flavored diet).
Step 4: Immediately following termination of Step
3, each demonstrator was randomly assigned to one of
two experimental groups or one of two control groups.
Demonstrators assigned to experimental groups each
received ip injection of 1% of body weight of 2% (w/
v) LiCI solution. Members of control groups were
injected with an equivalent volume of isotonic saline
solution.
Step 5: Immediately following injection, each
demonstrator was returned to its respective observer's
cage, and demonstrator and observer were allowed to
interact for either 30 min or 2 hr, depending on the
condition to which a given demonstrator-observer pair
had been assigned.
Step 6: Each demonstrator was removed from the
experiment, and each observer was offered, for 18 hr,
two weighed food cups, one containing cinnamon-
flavored diet and one containing cocoa-flavored diet.
30 Min
2 Days 1 Day 30 Min or 2 Hr TEST

.--0;0' coc
~-~-G -~~I-[E[
~ ~
O;o'CIN
o;o,c;:-~
1
or
Diet coe
LiCI (Experimental)
or
Saline (Control)
STEP 1 STEP 2 STEP 3
INJECTION
STEP 4 STEP 5 STEP 6
Figure J. Schematic diagram of the procedure of Experiment 1.
(0 = observer; D = demonstrator;
Diet CIN = cinnamon-flavored diet; Diet COC = cocoa-flavored
diet. Hatching indicates pellets of
Purina Laboratory Rodent Chow present in cage.)
Mingwen
Pencil
Mingwen

Pencil
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361
2 Days 1 Day 30 Min 15 Min INJECTION TEST
Diet COC
~-~--[G--rn-o-lli
~ /
1

'DleICIN
Diet CIN 8or ---+- DDiet CQe
liCI (Experimental)
or
Saline (Control)
Figure 3. Schematic diagram of the procedure of Experiment 2.
(See Figure 1 for abbreviations.)
served as observers, and an additional 32 rats 60-90
days of age served as demonstrators.
Procedure. The procedure (see Figure 3) was sim-
ilar to that described in Method of Experiment 1 (see
Figure 1) except that instead of injecting each dem-
onstrator immediately before it interacted with an
observer, we injected each observer immediately after
it interacted with a demonstrator. Observers in the
experimental group received 1% of body weight of 2%
(wjv) LiCI solution; observers in the control group
received an equivalent volume of isotonic saline solu-
tion. Fifteen minutes following injection, each ob-
server was offered, for 18 hr, a choice between weighed
samples of cocoa- and cinnamon-flavored diets.
presented in Figure 4 which indicates the
percentage of cocoa-flavored diet eaten by
observers whose demonstrators had in-
gested either cinnamon-flavored or cocoa-
flavored diet prior to their interaction with
observers. During testing, observers in the

control group exhibited a preference for the
diet their respective demonstrators ate,
while those in the experimental group ex-
hibited an aversion to the diet of their
respective demonstrators (Mann-Whitney
U tests, see Figure 4 for p values).
The results of the present experiment
indicate that cues received by observer rats
from demonstrators are adequate condi-
tional stimuli for the learning of an aver-
sion. It is, of course, possible that the avoid-
ance of demonstrators' diet exhibited by
subjects in the experimental group was not
the result of a learned aversion but rather
of an unconditioned response to toxicosis.
Experiment 3 was undertaken to directly
examine the unconditioned effects of toxi-
cosis on observers' preference for demon-
strators' diets.
Experiment 3
If the avoidance of demonstrators' diets
exhibited by observers were the result of an
unconditioned response to toxicosis, one
would expect observers poisoned prior to
interaction with demonstrators to exhibit
an aversion to demonstrators' diets.
Method
Subjects. Twenty-four experimentally naive 42-
day-old Long-Evans rats from the McMaster colony
served as observers. An additional 24 rats from the
same source, 2-3 wk older than observers, served as

demonstrators. Half of the observers and half of the
demonstrators were assigned to an experimental
group; the remainder, to a control group.
Procedure. Treatment of both experimental and
control groups is illustrated in Figure 5. In brief, on
the third day of the experiment, observers received ip
injection of 1% of body weight of a solution. The
OBSERVERS INJECTED
COC CIN COC CIN
DEMONSTRATORS'DIET
Figure 4. Mean amount of cocoa-flavored (COC) diet
ingested by observers as a percentage of total amount
eaten. (CIN = cinnamon-flavored diet. Bars indicate
:t 1 SE.)
362 B. GALEF, JR., S. WIGMORE, AND D. KENNETT
2 Days 1 Day INJECTION
~__~-O
r
LiCI (Experimental)
or
Saline (Control)
4 Hr 30 Min 15 Min TEST

I
~ I!"::l nDl
__Diet COC
· D ~--Lb--~--G
/
"'--Diet CIN
Diet CIN /
or D
Diet COC
Figure 5. Schematic diagram of the procedure of Experiment 3.
(See Figure 1 for abbreviations.)
observers in the control group were injected with
isotonic saline, and those in the experimental group
with 2% (w/v) LiCl solution. All observers were then
left undisturbed for 4 hr while subjects in the experi-
mental group recovered from acute effects of toxicosis
induction. Each observer then interacted for 15 min
with a demonstrator fed either cinnamon- or cocoa-
flavored diet, and each observer was subsequently
tested for its preference between cinnamon- and co-
coa -flavored diets.
presented in Figure 6 which indicates the
percentage of cocoa-flavored diet eaten by
observers whose demonstrators had in-
gested either cocoa- or cinnamon-flavored

diet. During testing, subjects in both con-
trol and experimental groups exhibited
marked preference for the diet their respec-
tive demonstrators had eaten (Mann- Whit-
OBSERVERS INJECTED
<II 100
a:
w
~ 90
w
~ 80
o
> 70aI
ffi 60
I-
~ 50
u
o 40
u
tu 30
is
;f'. 20
:i 10
w
::E
Saline Lithium Chloride
o
COC CIN COC CIN
DEMONSTRATORS'DIET

Figure 6. Mean amount of cocoa-flavored (COC) diet
ingested by observers as a percentage of total amount
eaten. (CIN = cinnamon-flavored diet. Bars indicate
:!: 1 SE.)
ney U tests, see Figure 6 for p values).
Experience of toxicosis does not in itself
result in avoidance by observers of the diet
eaten by demonstrators.
General Discussion
The results of the present series of ex-
periments indicate both (a) that cues emit-
ted by one rat, reflecting the identity of the
diet that rat has recently eaten, form an
adequate conditional stimulus for toxicosis-
based aversion learning (Experiments 2
and 3) and (b) that naive rats experiencing
the cues emitted by an ill conspecific pre-
viously fed a diet do not develop an aversion
to that diet (Experiment 1).
Given that the purpose of undertaking
this series of studies was to determine
whether a rat would avoid ingesting a diet
as the result of interacting with an ill con-
specific that had ingested that diet, the
failure to find such a phenomenon consti-
tutes a null outcome. Like all null outcomes
the present finding is difficult to interpret.
Taken together, the finding of Lavin et al.
(1980), that an ill rat is an adequate uncon-
ditioned stimulus for aversion learning, and
the finding in Experiment 2 above, that

cues emitted by a fed rat are an adequate
conditional stimulus for aversion learning,
suggest that under the proper set of exper-
imental parameters, one would find socially
mediated aversion learning.
Our reason for reporting the present re-
sults, rather than searching the relevant
parameter space until a situation in which
socially mediated aversion learning is ob-
tained, is to make clear that even if the
desired result is eventually found, there
must be serious question as to its relevance
to toxin-avoidance behavior of rats in nat-
363
ural environments. The more restricted the
parameter space in which socially mediated
learned aversions occur, the less likely they
are to play a role in the diet selection of
free-living organisms.
In more than 20 experiments on the so-
cially mediated transfer of diet preference,
we have invariably seen preference for dem-
onstrators' diet by observers (Galef, 1983;
Galef & Wigmore, 1983). Similarly Strupp
(in press-a, in press-b, Note 1) and Posa-
das-Andrews (1983; Note 2), using quite
different experimental paradigms, have re-
peatedly found social transfer of diet pref-
erence. This consistency of outcome across

a broad range of conditions suggests that
the social transmission of preference for a
diet is likely to playa role in natural envi-
ronments. The difficulty that both our lab-
oratory and that of Posadas-Andrews (Note
2) have experienced in demonstrating so-
cially mediated aversion learning suggests
that it is unlikely to be an important aspect
of the poison-avoidance behavior of free-
living animals. At the very least, any future
demonstration of social transmission by ill
rats of an aversion to a specific diet will
have to be critically examined to determine
whether the parameters allowing such
transmission to occur are likely to be found
in natural situations.
Reference Notes
1. Strupp, B. J. Personal communications, 1982,
1983.
2. Posadas-Andrews, A. Personal communication,
1982.
References
Bond, N. W. Transferred odor aversions in adult rats.
Behavioral and Neural Biology, 1982,35, 417-421.
Coombes, S., Revusky, S. H., & Lett, B. T. Long-delay
taste-aversion learning in an unpoisoned rat: Ex-
posure to a poisoned rat as the unconditioned stim-
ulus. Learning and Motivation, 1980, 11, 256-266.
Galef, B. G., Jr. Utilization by Norway rats (R. nor-

vegicWl) of multiple messages concerning distant
foods. Journal of Comparative Psychology, 1983, 97,
364-371.
Galef, B. G., Jr., & Wigmore, S. W. Transfer of infor-
mation concerning distant foods: A laboratory in-
vestigation of the "information-centre" hypothesis.
Animal Behaviour, 1983,31, 748-758.
Lavin, M. J., Freise, B., & Coombes, S. Transferred
flavor aversions in adult rats. Behavioral and Neural
Biology, 1980, 28, 15-33.
Posadas-Andrews, A., & Roper, T. J. Social transmis-
sion of food preferences in adult rats. Animal Be-
haviour, 1983,31,265-271.
Steiniger, F. von. Beitrage zur Soziologie und sonsti-
gen Biologie der Wanderratte. Zeitschrift fur Tier-
psychologie, 1950, 7,356-379.
Stierhoff, K. A., & Lavin, M. The influence of render-
ing rats anosmic on the poisoned-partner effect.
Behavioral and Neural Biology, 1982, 34, 180-189.
Strupp, B. J., & Levitsky, D. A. Early brain insult and
cognition: A comparison of malnutrition and hypo-
thyroidism. Developmental Psychobiology, in press-
a.
Strupp, B. J., & Levitsky, D. A. PKU, learning, and
models of mental retardation. Developmental Psy-
chobiology, in press-b.
Received April 2, 1983.
Revision received June 16, 1983 .

Social Interaction with an
Intoxicated Sibling Can Result
in Increased Intake of Ethanol
by Periadolescent Rats
Pamela S. Hunt
Jennifer L. Holloway
Elka M. Scordalakes
Department of Psychology
College of William & Mary
Williamsburg, VA 23187-8795
Received 13 December 1999; accepted 10 October 2000
ABSTRACT: A novel procedure for enhancing voluntary intake
of ethanol in periadolescent rats is
described. The procedure is a modi®cation of Galef et al.'s
(e.g., Galet, Kennett, & Stein, 1985; Anim
Learn Behave 13:25 ± 30) demonstrator± observer procedure.
Subjects were Sprague-Dawley rats,
28 ± 35 days of age. The experimental subject (observer)
interacted with a same-sex conspeci®c
(demonstrator) previously administered (a) 1.5 g/kg ethanol, (b)
an equal volume of water, or (c)
2.1% Sanka coffee intragastrically. Observers were tested with

24-hour access to ethanol and coffee
solutions. Observers that had interacted with demonstrators
administered ethanol ingested
signi®cantly more ethanol during the test than observers in the
other two groups. In Experiment 2
demonstrators were administered one of several doses of ethanol
(0.0, 1.0, 1.5, or 3.0 g/kg) and
observers' ethanol intakes were assessed. Only those observers
that interacted with 1.5 g/kg
demonstrators increased their ingestion of ethanol, relative to
water controls. The lower (1.0 g/kg)
and higher (3.0 g/kg) dose groups did not show altered ethanol
ingestion. These results are discussed
with respect to threshold levels of respired ethanol cues and the
ability of observers to detect these
cues from demonstrators. The demonstrator± observer procedure
appears to be effective for the
social transmission of preferences for ethanol in periadolescent
rats. ß 2001 John Wiley & Sons,
Inc. Dev Psychobiol 38: 101 ± 109, 2001
Keywords: ethanol; periadolescent rats; alcohol ingestion;
social learning
Alcohol abuse continues to be one of the most health-
costly issues in today's society, and the incidence of
alcohol abuse is ever-increasing. Particularly disturb-
ing statistics have recently been reported that the age
at which adolescents and young adults begin to
consume alcohol in rather large quantities is dropping

appreciably. A recent University of Michigan health
survey noted that 51% of 12th graders reported
drinking within the previous month and 26% of 8th
graders reported doing so. Binge drinking, de®ned as
having ®ve or more drinks on occasion, is also on the
rise, with 30% of all 12th graders and 16% of all 8th
graders reporting binge drinking at least once in the 2
weeks prior to the survey (National Institute on
Alcohol Abuse and Alcoholism, 1997).
Given the abuse potential for alcohol, and the
decreasing age at which alcohol is being consumed, it
is imperative that information be gained about the
causative factors involved in the initiation of drinking,
from both basic and applied research domains. To
Correspondence to: P. S. Hunt ([email protected])
Contract grant sponsor: National Institutes of Alcohol Abuse
and Alcoholism
Contract grant numbers: AA12135, AA12466
ß 2001 John Wiley & Sons, Inc.

adequately achieve these goals, there is also a need for
adequate animal models to examine relevant social,
environmental and genetic contributions to alcohol
consumption, especially early in development. Cur-
rent research using selectively bred rodent strains
continues to afford valuable insights into the role of
genetic predispositions toward alcohol consumption
and physical dependence (e.g., Brown, Tate, Vik, Haas,
& Aarons, 1999; Grahame, Li, & Lumeng, 1999;
Lumeng, Waller, McBride, & Li, 1982). However, it is
also recognized that genetic factors alone cannot
account for the widespread incidence of alcohol
abuse, either during adolescence or later in life (e.g.,
McKinzie et al., 1998). Experience also contributes
enormously.
As a means of examining experiential factors,
several paradigms have been developed to induce

ethanol intake in rats, a species valuable to addiction
and teratological research, but one that typically
avoids ethanol solutions. Many of the procedures that
result in increased intake of ethanol add confounding
stressor variables (e.g., Adams, 1995; Hansen, Fahlke,
Soederpalm, & Hard, 1995; Le et al., 1998; Roske,
Baeger, Frenzel, & Oehme, 1994), making the study
of mechanistic issues underlying the initiation of
voluntary ethanol intake dif®cult, if not impossible.
Moreover, these and other methods can involve rather
long training histories or complex motor require-
ments, making them unsuitable for use with young
rats because of their rapid rate of development and
relatively immature sensorimotor capabilities. A few
procedures have been speci®cally designed to exam-
ine the consequences of direct exposure to ethanol
cues during the preweanling period on subsequent
alcohol intake patterns (e.g., Bannoura, Kraebel,

Spear, & Spear, 1998; Hunt, Kraebel, Rabin, Spear,
& Spear, 1993; Hunt, Lant, & Carroll, 2000). To date,
however, the effects of direct social contact with an
intoxicated sibling on periadolescent animal's sub-
sequent willingness to ingest ethanol has not been
systematically examined.
It is known that rats detect and learn about foods
through olfactory cues present on the breath or peri-
oral region of a conspeci®c that has recently ingested
a particular food (e.g., Galef, Kennett, & Stein, 1985;
Galef & Stein, 1985; Posadas-Andrews & Roper,
1983; Strupp & Levitsky, 1984). In the experimental
preparation used to examine this social transmission
of dietary information, Galef and colleagues term the
animal that is fed a diet initially the `̀ demonstrator.''
The experimental subject, the one that is tested for
intake of that diet, is termed the `̀ observer.'' The
demonstrator is ®rst fed a diet with a particularly

salient olfactory component, such as chocolate, coffee,
or cinnamon. After the demonstrator has eaten the
food, it is introduced into a cage housing the observer
animal and the two are allowed to interact for a brief
period of time (e.g., 5 ± 30 min). The observer is then
given access to two diets simultaneouslyÐthe one
previously eaten by the demonstrator and another,
novel diet. In several reports, the observer animal was
found to preferentially ingest the diet eaten by its
demonstrator, even if the alternative is normally the
more preferred of the two. The effect is not one of
mere familiarity or simple exposure to the diet (Galef
et al., 1985), but requires a speci®c type of social
context to be established; that is, exposure to food
cues surrounding the peri-oral region of the demon-
strator (Galef & Stein, 1985; Galef & Wigmore, 1983).
Given the pervasive role of social behaviors in the
transmission of dietary information in rats (e.g., Galef,

Kennett, & Wigmore, 1984), it was hypothesized
that the same or similar processes might also act
when the food of interest is a drug of abuse, that is,
alcohol. Because ethanol is eliminated in unmeta-
bolized form through routes such as respiration and
salivation (Hollstedt & Rydberg, 1985) these cues
would be present on the breath of an organism follow-
ing ingestion of alcohol.
We have recently shown that this type of socially
mediated learning can be applied to alcohol intake in
preweanling animals (Hunt et al., 2000). In that study,
the observers were pups ranging in age from 8 to 16
days. After a brief period of social deprivation these
subjects were allowed to interact with a sibling that
had been intragastrically administered a 1.5 g/kg dose
of ethanol or water. Following this interaction, pups
were tested for voluntary intake of ethanol by infusing
ethanol into the mouth via an intra-oral cannula (Hall

& Rosenblatt, 1977). Observers that had interacted
with demonstrators administered ethanol ingested
signi®cantly more ethanol during the test than those
observers that had interacted with demonstrators
administered water.
The purpose of the present experiments was to test
the role of this type of social context in modifying
voluntary ethanol intake in periadolescent Sprague-
Dawley rats. The subjects ranged in age from 28 to 35
days at the beginning of the experiment, considered to
encompass the periadolescent period (Spear & Brake,
1983). In the experimental preparation, the subject of
interest (the observer) interacted with an animal (the
demonstrator) that had previously been force-fed
ethanol. Following this interaction, the observer was
tested for intake of ethanol versus coffee in a two-
bottle test. In two experiments the effectiveness of
this preparation for increasing observers' voluntary

ethanol intake was shown.
102 Hunt, Holloway, and Scordalakes
EXPERIMENT 1
The purpose of Experiment 1 was to determine whether
the demonstrator± observer preparation (Galef et al.,
1985) would be an effective means by which to
promote voluntary intake of ethanol in periadolescent
rats (cf., Hunt et al., 2000). Our choice of periadoles-
cent rats for subjects was in¯uenced by our interest in
adolescent alcohol intake and the social factors that
may contribute to the initiation of drinking. Addi-
tionally, this age allowed for the use of a two-bottle
test, potentially providing more information than that
available when testing preweanlings about alcohol
choice behavior.
Methods
Subjects. The subjects were 30 pairs of same-sex
sibling Sprague-Dawley-derived rats (16 female, 14

male), representing seven different litters. No more
than one male and one female from each litter served
as observers in each treatment group. The subjects
ranged from 30 to 35 days of age at the beginning of
the procedure. All animals were born and reared in the
psychology department vivarium at the College of
William & Mary. Breeders were housed together in
50.8�40.6�21.6 cm3 clear polycarbonate cages
with pine chip bedding and free access to food
(ProLab, St. Louis, MO) and water. Cages were
checked daily for births. Two days after birth (day of
birth�Postnatal Day [PD] 0) litters were culled to
8 ± 10 pups. Animals were maintained on a 12:12 hr
light:dark cycle with light onset at 0700 hr in the
temperature-controlled vivarium. On PD21 pups were
weaned and group-housed with same-sex littermates
in 50.8�40.6�21.6 cm3 clear polycarbonate cages
with ad lib access to food and water until the ®rst day
of the experiment. All procedures were approved by

the College of William & Mary Research on Animal
Subjects Committee and followed guidelines estab-
lished by the International Society for Developmental
Psychobiology.
Apparatus. All training and testing occurred in indi-
vidually sized stainless steel hanging cages located in
a room adjacent to the main vivarium, and maintained
on the same temperature and light control systems.
Demonstrators were intragastrically administered
ethanol, water, or coffee solutions using 12-cm lengths
of polyethylene tubing (PE-50; Clay Adams) attached
to 5-cc disposable syringes. Observers were tested for
intake of ethanol and coffee using 50-ml graduated
borosilicate drinking tubes with curved sipper spouts
that were attached to the outside of the hanging cages.
Procedure. The experiment was conducted over 5
days and is outlined in Table 1. On days 1 and 2 of
the procedure, same-sex siblings were pair-housed in
metal hanging cages and handled for approximately

2 min each day. At this time animals within each pair
were assigned to be the demonstrator or the observer.
On Day 3, the demonstrator was removed from the
home cage and placed alone in an adjacent hanging
cage. The demonstrator was given free access to both
food and water, while at this time the observer was
water-deprived but continued to have free access to
food.
On Day 4, 23 hr following separation and the
initiation of water deprivation, demonstrators were
weighed to the nearest 0.1 g. Next, the demonstrator
was intragastrically administered a 1.5 g/kg dose of
12.0% v/v ethanol solution (EtOH, n�10), an equal
volume of 2.1% w/v Sanka decaffeinated coffee (COF,
n�9), or an equal volume of the tap water vehicle
(WATER, n�10). One pair of male COF subjects was
eliminated from the experiment because of improper
intubation. Following intubation, demonstrators were
returned to their cages for 30 min. The 30-minute
period was selected because it has been shown to be

suf®cient for attaining approximately peak blood ±
alcohol levels and respiratory/salivary elimination
of alcohol cues (Molina & Chotro, 1989a; Molina,
Chotro, & Spear, 1989; Pohorecky & Brick, 1982).
The demonstrator was then placed into the observer's
cage and the two animals were left undisturbed for 30
min. After the interaction phase the demonstrator was
once again removed from the observer's cage.
Observers (34 ± 39 days at test) were then offered
two graduated drinking tubes; one containing a 5.6%
v/v ethanol solution and the second containing a 2.1%
Table 1. Procedure Used for Experiments 1 and 2
Day/time Procedure
1/10:00 am Pair-house demonstrators and
observers
Handle subjects 2 min
2/10:00 am Handle subjects 2 min
3/10:00 am Remove demonstrator and individually

house animals
Water deprive observers
4/9:00 am Weigh demonstrator
i.g. administration of EtOH, WATER,
or COF
4/9:30 am Demonstrators placed into observers'
cages
4/10:00 am Demonstrators removed
Two-bottle test begins (observer)
5/10:00 am End of two-bottle test
Periadolescent Ethanol Intake 103
w/v Sanka decaffeinated coffee solution. Both test
solutions were prepared with tap water and the
concentrations of each were chosen on the basis of
preliminary data (Scordalakes & Hunt, unpublished
data) indicating an equal preference for these solu-
tions in naõÈve animals. Observers were allowed free

access to both solutions for 24 hr. The left ± right
placement of the drinking bottles containing the two
solutions was counterbalanced across subjects in all
conditions to avoid a side-preference bias in the data.
At the end of the testing interval, the volume of each
solution ingested (ml) was recorded. The data were
also expressed in terms of the dose of ethanol ingested
during the 24-hour test period (g/kg/day).
Results
The data from this experiment are shown in Figure 1
and Table 2. It was predicted that EtOH observers,
those that had interacted with demonstrators adminis-
tered ethanol, would ingest more ethanol during the
test than WATER controls. Furthermore, observers
interacting with demonstrators administered coffee
(COF) were expected to ingest more coffee than
WATER controls (cf. Galef & Stein, 1985). The ®rst
prediction was realized. Observers that had interacted

with EtOH demonstrators exhibited increased intake
of the ethanol solution relative to coffee. Second, and
in contrast to what was predicted, observers that had
interacted with COF demonstrators did not exhibit
altered intake of coffee relative to that observed in the
WATER controls. When the data were expressed as a
daily dose of ethanol ingested (g/kg/day), again the
observers that had interacted with demonstrators
administered ethanol ingested a higher dose of ethanol
than controls.
The ethanol and coffee intake data were analyzed
using a 3 (demonstrator solution)�2 (test solution:
ethanol or coffee)�2 (gender) mixed-design analysis
of variance (ANOVA). This analysis yielded a signi-
®cant main effect of test solution [F (1,23)�6.23,
p < :05]. The demonstrator solution � test solution
[F (2,23)�4.85, p < :05] and test solution�gender
[F (2,23)�5.93, p < :05] interactions were also sig-
ni®cant. Post hoc comparisons conducted with Neu-
man ± Keuls tests revealed that the EtOH observers
ingested more ethanol and less coffee than either

the WATER or COF observers. Additionally, male
observers ingested more of the ethanol solution than
females, regardless of prior experience. Finally, total
¯uid intake during the test did not differ as a function
of group assignment. A 3 (demonstrator solution)�2
(gender) ANOVA conducted on the dose (g/kg/day)
data revealed signi®cant main effects of demon-
strator solution [F (2,23)�5.37, p < :05] and gender
[F (1,23)�7.87, p < :01]. Observers interacting with
ethanol-administered demonstrators ingested a higher
dose of ethanol during the test, and males ingested a
higher dose of ethanol than females, regardless of group.
Discussion
Results of the ®rst experiment indicate that an ob-
server animal will increase its intake of a 5.6% v/v
FIGURE 1 Mean (�SEM) intakes of ethanol and coffee
(ml) by observers in Experiment 1 during a 24-hour two-
bottle choice test. Observers had previously interacted for
30 min with demonstrators that had been intragastrically
administered a 1.5 g/kg dose of ethanol (EtOH), an equal

volume of tap water (WATER) or an equal volume of 2.1%
Sanka coffee (COF).
Table 2. Mean (�SEM) Dose of Ethanol (g/kg/day)
Ingested During the 24-Hour Two-Bottle Ingestion Test
for Experiments 1 and 2
Experiment 1
Observer group
EtOH 9.45 (1.13)
H2O 5.80 (0.98)
COF 5.97 (0.99)
Experiment 2
Demonstrator dose
0.0 5.69 (0.77)
1.0 6.45 (1.10)
1.5 8.16 (0.67)
3.0 5.96 (0.75)

ethanol solution following a brief (30 min) interaction
with an intoxicated sibling. Presumably, the adminis-
tration of ethanol to the demonstrator resulted in the
elimination of unmetabolized ethanol that was dete-
cted by the observer. By experiencing these ethanol
cues in the context of social interactions, the observer
acquired suf®cient information about ethanol to guide
later voluntary choice of this drug. In contrast to the
®nding of increased ethanol ingestion in EtOH
observers, animals that had interacted with demon-
strators administered a coffee solution showed no
socially mediated change in coffee preference (but see
Galef & Stein, 1985). It is possible that the time
between administration of coffee to the demonstrator
and the interaction phase, or characteristics of the
coffee solution intubated, may have affected the
observers detecting and learning about the coffee cue
from the demonstrators.

The work of Galef and colleagues (Galef & Stein,
1985; Galef & Wigmore, 1983) has repeatedly indi-
cated that physical contact per se is not a necessary
component of this type of learning. Observers have
been found to acquire dietary information from de-
monstrators even when the animals are separated by a
wire mesh screen or when demonstrators are anesthe-
tized. There is, however, a lack of data on preweanling
and periadolescent animals. The availability for social
interactions may in fact enhance the strength of diet
acquisition in younger animals more so than in adults.
Several laboratories have shown that social interac-
tions and the opportunity for play are highly rein-
forcing to adolescent age rats. Most of the research in
this area has utilized the conditioned place preference
paradigm, in which one arm of a T-maze contains a
play partner while the alternative arm contains no
stimulus, a surrogate animal, or an animal that does

not engage in play behavior. Using variants of this
paradigm, adolescent rats have consistently been
shown to prefer the arm previously associated with
a play partner (e.g., Calcagnetti & Schechter, 1992;
Crowder & Hutto, 1992; Humphreys & Einon, 1981;
Normansell & Panksepp, 1990). In the present proce-
dure the demonstrators and observers were allowed to
physically interact following a period of social isola-
tion. It is unclear at present whether or not this
physical contact had the effect of promoting acquisi-
tion of appetitive responses toward ethanol.
EXPERIMENT 2
In Experiment 1 the EtOH demonstrators were ad-
ministered a 1.5 g/kg dose of ethanol. This dose was
chosen on the basis of a series of reports by Molina
and colleagues (Molina et al., 1989; Molina & Chotro,
1989b) indicating that 1.5 g/kg ethanol, but not lower
doses, resulted in detectable levels of ethanol orosen-

sory cues suf®cient for learning about those cues to
occur. In the Molina studies, the animal that was
administered the ethanol intragastrically was assessed
for its own learning about alcohol in terms of olfactory
preferences and alcohol intake. The results of the
present Experiment 1 indicate that another animal can
detect and learn about these cues as well. It is possible
that with the demonstrator± observer procedure doses
lower than 1.5 g/kg would be effective for producing
suf®cient elimination of ethanol to affect the alcohol
intake of an observer. The purpose of Experiment 2
was to conduct a dose ± response study to determine
(a) whether demonstrators administered a dose of
ethanol lower than 1.5 g/kg would provide suf®-
cient orosensory stimuli to promote ethanol intake
in observers and (b) whether demonstrators adminis-
tered a dose higher than 1.5 g/kg would establish
even stronger preferences for the ethanol solution in

observers. In this experiment demonstrators were
intragastrically administered 0, 1.0, 1.5, or 3.0 g/kg
ethanol.
Methods
Subjects. The subjects in this experiment were 48
pairs of same-sex sibling Sprague-Dawley-derived
rats (24 male, 24 female), representing 14 different
litters. Subjects ranged in age from 28 to 33 days on
the ®rst day of the procedure. Animals were born and
reared in the psychology department vivarium at the
College of William & Mary under conditions identical
to those described in Experiment 1. Pairs of animals
were randomly assigned to one of four conditions,
designated according to the dose of ethanol adminis-
tered to the demonstrator: 0 (n�12), 1.0 (n�12), 1.5
(n�12), or 3.0 g/kg (n�11). One pair of female
subjects assigned to the 3.0 g/kg group was eliminated
from the study due to the improper intubation of the
demonstrator.
Procedure. The experimental procedure was similar

to that of Experiment 1, except for a change in coffee
concentration and the dose of ethanol administered to
the demonstrators. Following 2 days of pair housing
in hanging cages, demonstrators were removed and
placed in an adjacent cage. Observers were then
water-deprived. Demonstrators were intragastrically
administered one of three doses of a 12.0% v/v ethanol
solution prepared in a tap water vehicle: 1.0, 1.5, or
3.0 g/kg. A water-intubated control group (0 g/kg) was
administered a volume of tap water equal to the
volume administered to the 1.5 g/kg EtOH group.
Thirty minutes following intubation, the demonstrator
was placed into the observer's cage and the two
animals were allowed to interact for 30 min. The
demonstrator was again removed and the observer
was given a 24-hour test of intake of 5.6% v/v ethanol

vs. 1.8% w/v Sanka coffee. The concentration of the
coffee solution was decreased in order to reduce
baseline ethanol preference. This allowed us to more
clearly address the question of whether the preference
for ethanol established through interactions with a 3.0
g/kg demonstrator would be greater than that with a
1.5 g/kg demonstrator. The volume of each solution
ingested by the observers was recorded, and the data
were also expressed in terms of the dose of ethanol
ingested (g/kg/day).
Results
The data from this experiment are presented in Figure
2 and Table 2. As can be seen in the ®gure, observers
that had interacted with demonstrators administered
1.5 g/kg ethanol exhibited an increased intake of
ethanol vs. coffee, and therefore a higher daily dose of
ethanol consumed, replicating the results of Experi-
ment 1. However, observers that had interacted with

demonstrators administered either a lower (1.0 g/kg)
or a higher (3.0 g/kg) dose of ethanol failed to exhi-
bit a reliable change in ethanol intake. Finally, the
water observers (0 g/kg) showed approximately equal
intake of both solutions, similar to that observed in
Experiment 1.
A 4 (demonstrator dose)�2 (test solution)�2
(gender) ANOVA conducted on the intake data
revealed only a signi®cant main effect of gender [F
(1,39)�4.18, p < :05]. Generally, males ingested
more ¯uid during the test than females, although there
were no differences in terms of the proportions of
ethanol and coffee. Follow-up ANOVAs [2 (demon-
strator dose)�2 (test solution)] were used to compare
intakes of the 0.0 g/kg group with each of the other
groups. The only reliable demonstrator dose� test
solution interaction occurred for the 1.5 g/kg obser-
vers that exhibited increased intakes of ethanol, and
reduced intakes of coffee, relative to the water (0.0 g/
kg) controls [F (1,22)�5.77, p < :05]. The analyses
comparing the 0.0 with the 1.0 g/kg and 3.0 g/kg

groups, respectively, revealed no signi®cant diffe-
rences. The analyses of the ethanol dose ingested
yielded comparable results (see Table 2). The 4
(demonstrator dose) �2 (gender) ANOVA revealed
no signi®cant effects or interactions. Planned t-tests,
however, indicated that the dose of ethanol ingested
by the 1.5 g/kg observer group was signi®cantly
higher than that ingested by the water control group
[t (22)�2.36, p < :05]. No other differences were
statistically reliable.
Discussion
The results of Experiment 2 once again indicated that
observers that had brie¯y interacted with an intoxi-
cated sibling exhibited increased intake of ethanol
during a two-bottle choice test. Furthermore, there
was an inverted-U dose ± response relationship. Obser-
vers interacting with siblings given a 1.5 g/kg dose of
ethanol did increase their intake of ethanol; however,
observers interacting with siblings administered either

a lower (1.0 g/kg) or a higher (3.0 g/kg) dose failed to
exhibit altered ethanol ingestion.
The failure to obtain increased ethanol intake in
the low (1.0 g/kg) dose condition is likely due to
insuf®cient olfactory cues present on the breath of the
demonstrator animals. Decreased salience of these
cues would correspondingly reduce the ability of
observers to detect and/or learn about alcohol from the
demonstrators (cf. Molina & Chotro, 1989b). This
social modulation of ethanol intake can easily be
viewed within a Pavlovian conditioning perspective,
for which the ethanol olfactory cues detected on a
conspeci®c's breath serve as the conditioned stimulus
(CS) and some aspect of the social interaction serves
FIGURE 2 Mean (�SEM) intakes of ethanol and coffee
(ml) by observers in Experiment 2 during a 24-hour two-
bottle choice test. Observers had previously interacted for
30 min with demonstrators that had been intragastrically

administered 0, 1.0, 1.5, or 3.0 g/kg ethanol.
as the unconditioned stimulus (US). It is well known
that characteristics of the CS, as well as the US, can
in¯uence the rate and asymptotic level of conditioning
(e.g., Pearce & Hall, 1980; Rescorla & Wagner, 1972).
If the amount of respired ethanol cues is not of
suf®cient intensity, then minimal conditioning would
be expected. Therefore, little or no conditioned res-
ponse (ethanol intake above 50%) would be expected
to occur. This is precisely what was observed in
Experiment 2.
A different explanation, however, is required to
describe the failure of the 3.0 g/kg observers to exhibit
an ethanol preference. First, it is possible that the
severely intoxicated demonstrator was capable through
some means of communicating an aversion for ethanol

to the observer (but see Galef, Wigmore, & Kennett,
1983). The post-ingestional consequences of a dose of
3.0 g/kg ethanol have been found to condition taste
aversion to a concurrently presented sucrose solution,
at least in younger animals (Hunt, Spear, & Spear,
1991). Furthermore, preweanling rats administered a
3.0 g/kg dose will subsequently avoid both ethanol
odor and taste (e.g., Molina et al., 1989). It is therefore
possible that a severely intoxicated demonstrator
could transmit cues that serve to communicate even
a weak ethanol avoidance to an observer, one that was
capable of counteracting an established preference.
A second explanation for the failure of 3.0 g/kg
observers to acquire a preference for ethanol centers
on the ability of the observers to detect the ethanol
cues from the demonstrators. Clearly if the salience of
the CS in part determines the strength of conditioning,
then the intensity of the cues resulting from this high

dose of ethanol should be even greater than those from
the 1.5 g/kg condition (Hollstedt & Rydberg, 1985;
Pohorecky & Brick, 1982). Although the concentra-
tion of these cues might in fact be greater, the question
remains as to whether the observers were actually able
to detect these cues from the demonstrator. Casual
observation of the 3.0 g/kg demonstrators indicated
an almost complete lack of movement during the
30-minute interaction period; demonstrators tended to
lie in a prone posture with their mouths directed
toward the bottom of the cage. Although quantitative
measurements of peri-oral contact between demon-
strators and observers were not made, it is possible
that the observers were unable to detect the ethanol
cues emanating from the peri-oral region of the
3.0 g/kg demonstrators. In the absence of adequate
detection of ethanol orosensory cues, the transmission
of ethanol information from demonstrator to observer

would not occur. By this account then, the failure of
these observers to exhibit modi®ed ethanol ingestion
resulted from an inability to learn about ethanol.
GENERAL DISCUSSION
Among the ways that human infants, young children,
and adolescents can be exposed to alcohol in the
context of the home and other social environments is
through the detection of ethanol in the milk of a
breast-feeding mother, long-term exposure to the odor
of ethanol, direct topical application (e.g., for relief of
teething pain), and/or the detection of respired ethanol
cues (e.g., Fossey, 1993; Mennella & Beauchamp,
1991, 1993; Noll, Zucker, & Greenberg, 1990). It has
been suggested that young children acquire informa-
tion about alcohol via such types of exposure. Noll
et al. (1990) reported that children whose parents were
heavy drinkers were more likely to correctly identify
the odor of alcohol than children whose parents drank

only moderately or not at all. Another study reported
similar results from a cohort of Scottish and British
children (Fossey, 1993). In this study, the children
were capable of correctly identifying alcohol by smell
on over 80% of the occasions presented. Whether
exposure to ethanol cues in these situations would be
suf®cient to modify a human's later choice and
acceptance of this drug is not yet known.
Such experiential factors may indeed contribute
substantially to the initiation of alcohol drinking in
children and adolescents. It is known that children of
alcoholics tend to drink more than children of non-
alcoholics (U.S. Department of Health and Human
Services, 1993). Although genetics no doubt play an
important role here, the home environment is likely to
also be extremely important. Children of alcoholics
would spend more time in contact with alcohol-
related cues, potentially affecting these children's

learning of positive responses toward this drug.
In animal studies designed to model such situations,
young rats have consistently been shown to increase
their acceptance of ethanol following each type of
exposure. These results are highly suggestive that early
experiences with alcohol cues can impact alcohol inges-
tion patterns. For example, Hunt et al. (1993) investi-
gated alcohol intake in preweanling rats following
exposure to ethanol during a bout of nursing. Pups
12 ± 16 days of age increased their intake of ethanol
after experiencing alcohol-contaminated milk in con-
junction with the opportunity to suckle. Pepino,
Kraebel, Lopez, Spear, and Molina (1998) have addi-
tionally reported that exposure to alcohol-contami-
nated milk can result in altered motor and cardiac
responsivity toward ethanol cues in preweanlings.
Bannoura et al. (1998) raised rat pups from birth to
weaning in cages that were continuously scented with

ethanol odor. These pups exhibited a clear preference
for ethanol when tested for intake after weaning,
compared with controls not exposed to ethanol cues.
These ®ndings could re¯ect a conditioned preference
for ethanol odor experienced in the context of social
interactions with the dam and littermates, or the effect
of familiarity from long-term repeated exposure
(Bronstein & Crockett, 1976; Leon, Galef, & Behse,
1977).
Once ingested, a proportion of the ethanol dose is
distributed throughout the body in unmetabolized
form and is expired via its accumulation in the lungs.
Additional routes of nonhepatic elimination involve
salivation, urination, and perspiration (Hollstedt &
Rydberg, 1985). Regardless of the actual route of
elimination, animals are known to be capable of

detecting these cues and learning about them in a
variety of experimental preparations in which social
contact with other animals is a critical feature (e.g.,
Bannoura et al., 1998; Chotro, Kraebel, McKinzie,
Molina, & Spear, 1996; Hunt et al., 2000). Hunt et al.
reported that social interactions with an intoxicated
sibling result in enhanced intake of ethanol by pre-
weanling animals, ranging in age from 8 to 16 days.
These results, along with those of previous research
(e.g., Chotro et al., 1996) indicate that exposure to
ethanol in social contexts can play a role in modifying
a preweanling animal's responsiveness toward etha-
nol. The results of the present experiments indicate that
a periadolescent rat will also acquire information
about alcohol cues from an intoxicated sibling, and as
a result will increase its subsequent intake of an etha-
nol solution. It is, however, unclear at this time, whether
or not exposure to ethanol-derived cues in these

situations would have a relatively long-term impact on
later alcohol choice (but see Galef, 1989; Hunt et al.,
2000, Experiment 3; Strupp & Levitsky, 1984).
Clearly, research is beginning to identify ways in
which early experiences involving direct exposure to
ethanol cues in the context of the home environment
can affect young organisms' later acceptance of this
drug. Continued investigation into the nature of the
alcohol cues detected, and the mechanisms through
which various types of learning take place, may help
to further elucidate the consequences of social learn-
ing for alcohol abuse in late childhood and adoles-
cence. Moreover, the present experimental procedure
may afford a relatively simple and robust experimental
situation in which to further study the role of social
experiences with alcohol in the initiation, and possibly
also the maintenance, of excessive ethanol intake.
NOTES

This research was supported by grants AA12135 and
AA12466 from the National Institutes of Alcohol
Abuse and Alcoholism to P.S.H.. Experiment 1 was
conducted as part of the requirements for a B.S. with
honors in biological psychology by E.M.S., and
Experiment 2 was conducted as part of the require-
ments for a master's degree in psychology by J.L.H..
We are grateful to Elena Cuticelli for her assistance
with data collection.
REFERENCES
Adams, N. (1995). Sex differences and the effects of tail
pinch on ethanol drinking in Maudsley rats. Alcohol, 12,
463 ± 468.
Bannoura, M. D., Kraebel, K. S., Spear, L. P., and Spear,
N. E. (1998). Effects of preweanling ethanol odor expo-
sure on ethanol preference. Alcohol, 15, 213 ± 217.
Bronstein, P. M., & Crockett, D. P. (1976). Exposure to the
odor of food determines the eating preferences of rat

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