1. Abstract
Evolutionary theory predicts that animal behavior is generally governed by
decision rules (heuristics) which adhere to ecological rationality: the tendency to make
decisions that maximize fitness in most situations the animal encounters. However, the
particular heuristics used by ant colonies of the genus Temnothorax and their propensity
towards ecological rationality are up for debate. These ants are adept at choosing a nest
site, making a collective decision based on complex interactions between the many
individual choices made by workers. Colonies will migrate between nests either upon the
destruction of their current home or the discovery of a sufficiently superior nest. This
study offers a descriptive analysis of the heuristics potentially used in nest-site decision-
making. Colonies were offered a choice of nests characterized by the Ebbinghaus
Illusion: a perceptual illusion which effectively causes the viewer to perceive a circle as
larger when it is surrounded by small circles than when that same circle is surrounded by
large circles. Colonies were separated into two conditions: in one, they were given the
option to move to a high-quality nest surrounded by poor-quality nests, and in the other
they were given the option to move to a high-quality nest surrounded by medium-quality
nests. The colonies in the poor condition were found to be more likely to move to the
good nest than were colonies in the medium condition at a statistically significant level.
That is, they responded to the Ebbinghaus Effect in the way that is normally expected.
This result was discussed in terms of its implications for the ecological rationality of the
nest-site choice behavior of these ants.
[1]

2. Introduction
Rational behavior is characterized by the process of maximizing personal
advantage through one’s pattern of choices. A set of decisions is observed to be rational if
it maximizes some hidden currency of an individual without violating a sense of
consistency in the valuations. Namely, four primary axioms—which satisfy intuition—
constitute a rational actor according to expected utility theory: completeness (and
dominance), transitivity, continuity, and independence. According to completeness, an
individual either prefers A to B or B to A, or is indifferent between the two for every
alternative A and B, and dominance claims that the preferred option should be chosen.
Transitivity assumes that preferring A to B and B to C therefore constitutes preferring A
to C, such that an individual will make decisions with transitive consistency. Continuity
assumes that if an individual prefers A to B and B to C, then there is some mixture (of
probabilities) of A and C which is equally preferred to B. Lastly, the axiom of
independence assumes that preference order in a set of two options will remain the same
after the addition of a third option to the set (von Neumann and Morgenstern 1944).
This theory of utility maximization has proved most appropriately suited to
normative economics which describes limited, idealized models. Though the theory’s
normative qualities appear to be reasonable predictors of behavior, they have been
exposed to experimental scrutiny in many situations and revealed to be descriptively
inaccurate (Tversky and Kahneman 1986). Where normative economics is the study of
what people ought to do, positive economics attempts to describe what people actually do
(Friedman 1953). Experimental economics is often adopted when normative conclusions
[2]

3. are observed to be consistently violated. It enables economists to arrive at correct
predictions of behavior by allowing for deviations from normative decision-making.
Though models of rationality have been thoroughly studied with both real and
ideal human subjects, the subjects of this paper are ant colonies. Temnothorax rugatulus
is a species of rock ant which primarily dwells in flat rock crevices (Pratt 2010).
Colonies will migrate between nests both upon the destruction of their current home or
the discovery of a sufficiently superior nest. Though the urgency of replacing a
compromised nest requires quicker decision-making than in the case of passively
browsing, both instances use the same processes and typically achieve the same results
(Franks et al. 2009, Pratt 2005). These ants (the Temonthorax genus in general)
ultimately choose a nest site based on simple rules of preference, viability, and
commitment. The first set of rules outlines their preferences: simple experiments of nest
choice have confirmed that the ants prefer nests with small entrances, few entrances,
adequate size, and dark interiors. The scout who experiences a nest option accounts for
these preferences while also determining the nest’s spatial capability to house the entire
colony (and future growth) by following a second rule (Pratt and Pierce 2000). She will
pace the floor area on several occasions and release an individual-specific pheromone
trail (Mallon 2000). On every subsequent visit, she measures the frequency at which she
crosses her own path to conclude how large or small the area must be (Mugford and
Mallon 2001). Then, if she understands the nest to be better than her home based on all of
her preferences (for light level, entrance size, capacity, etc.), she will return to the colony
to find another ant and recruit her to the site via a slow procedure called tandem running.
The new scout will assess the nest on the aforementioned dimensions and possibly recruit
[3]

4. another ant to do the same. Each newcomer will then be responsible for adhering to yet
another rule: the quorum rule. If a certain threshold of ants are found lingering in the nest,
the scouts will switch from slow tandem runs to fast transports in which colony members
are quickly carried from the old home to the new nest until the colony migration is
complete (Pratt 2010).
A normative rational choice model with regard to social insects can be described
as the pattern of decisions which produces fitness-maximizing outcomes. Behavioral
ecologist Alex Kacelnik called this notion B-rationality—‘B’ for Biological (Kacelnik
2006). Normatively, a biologically rational individual is one whose phenotype has been
governed by natural selection to maximize (inclusive) fitness. Though fitness choice is
not constrained to the same axioms of expected utility maximization, it dictates that ideal
decisions will be made (at least for the species in the long run) in the majority of
circumstances an individual faces. This idea was originally presented and termed
ecological rationality by Gigerenzer and Todd (1999) who defined the concept as the
“adaptive behavior resulting from the fit between the mind’s mechanism and the structure
of the environment in which it operates.” Ecological rationality emerges from an animal’s
implementation of a variety of useful decision rules, including both vigilant maximization
as well as helpful rules of thumb (heuristics). Theoretically, this decision-making process
could be measured and studied to offer predictability of behavior, but identifying which
choices are actually beneficial for an individual’s fitness can be a haphazard
undertaking—especially over the course of localized state changes: for instance, if the
timing or ordering of decisions appears to violate transitivity yet is truly the most
advantageous policy according to fitness value. Therefore, it is generally accepted that
[4]

5. the normal and consistent behavior of animals in their natural environment is ecologically
rational behavior (Houston et al. 2007).
On the other hand, a descriptive study of these ant colonies’ decision-making
process may reveal a decision rule used to choose between nest options: namely, that of
piecemeal comparison rather than maximization with complete information. Species rely
on heuristics both because they are limited by cognitive resources and because heuristics
facilitate fast and frugal calculations (Gigerenzer and Todd 1999). One such heuristic to
decision-making is that of comparative evaluation. For instance, an animal may be less
inclined to estimate the raw fitness value of each option in a set than to evaluate pairwise
comparisons (Bateson et al. 2003). In contrast to choosing the utility-maximizing option
of available alternatives, selecting by comparisons is valuing the differences between
outcomes with unequal weights.
Comparative evaluation has been explored in the process of choosing a mate as
well as in foraging decisions and there is compelling reason for why some species might
have evolved with such heuristics. In particular, mate choice is a decision process which
involves many options to the extent that an individual would not be able to remember the
exact value of each potential mate, but she could conceivably loop through every choice,
keeping track of which contender stands out in comparison. The variation observed in
preferences for sexual signals supports the hypothesis of the existence of a comparative
heuristic (Bateson 2005). Additionally, foraging behavior among honeybees has
demonstrated violations in the rationality axiom of transitivity in decision-making (Shafir
1994). This result is understandably attributed to a comparative evaluation mechanism in
[5]

6. which comparisons give more weight to an option than its raw valuation otherwise
would.
Though heuristics like these may chiefly result in rational (fitness-maximizing)
decisions, their use has been shown to yield systematic mistakes in the process of optimal
decision-making (Livnat and Pippenger 2008). Ecological rationality lends itself to
incompleteness. If a heuristic is found to underperform in a specific situation, it can be
repeatedly tested and will elicit the same limitation, isolating a particular cognitive bias
(Ariely 2008). However, if the experimental framework fails to realistically resemble the
subject’s natural environment, then the heuristic in question cannot justly be deemed an
ecologically irrational bias (McNamara et al. 2014). Thus, the goal of this study was to
create an ecologically valid experimental paradigm through which the collective
decisions of ant colonies could be tested for ecological rationality on the basis of a
particular applied decision rule.
This paper explores the nest choice behavior of ant colonies which also exhibits
some of the challenges faced both in mate choice and foraging. In the ants’ natural
environment, there are many nest sites to choose from (sometimes far away from each
other), so their ability to store accurate information of every opportunity is questionable.
In the lab, the ants have been known to fail to uphold house-hunting hypotheses by way
of displaying different preferences in otherwise identical situations under the assumption
of absolute evaluation (Sasaki and Pratt 2011). Therefore, the nest choice process is also
embraced as a candidate which is aided by a comparative evaluation mechanism.
Evaluation based on the comparison of alternatives is particularly vulnerable to
the decoy effect, a cognitive bias which departs from rationality. In its simplest form, the
[6]

7. decoy effect occurs when the addition of a strictly-dominated option to a choice set
changes preferences for the initial options. This creates a situation in which the
dominating target is the clear winner in all pairwise comparisons, thus enhancing its
attractiveness for individuals using comparative heuristics. It can also cause an individual
to value the pairwise differences of relevant characteristics between a target and non-
targets with unequal weighting, causing the target to seem more attractive when
compared to the least attractive non-target than when compared to others. This cognitive
bias also comes in the form of the asymmetrically-dominated effect in which an option
dominated on only a subset of dimensions alters preferences for the other options. Prior
research has concluded that several species may use comparative evaluation as observed
in binary and trinary trials with asymmetrically dominated decoys (Bateson 2004).
Alternatively, an immunity to decoy effects as suggested by past research would
maintain that nest site choice is consistent with regularly maximizing fitness (Edwards
and Pratt 2009). In particular, researchers found that though individuals may be flustered
when given a scenario of decoys, colony-level decisions are apt to bypass the
asymmetrically-dominated decoy effect (Sasaki and Pratt 2011). That is, when presented
with a decoy, the colonies maintained an equivalent preference distribution between
equally-preferred targets as they did without a decoy present. However, the current study
attempts to highlight comparative evaluation by removing asymmetrical domination,
varying nest choices by a single dimension only.
The decoy nests in this study were arranged on the basis of the Ebbinghaus Effect.
Traditionally, the Ebbinghaus Illusion is a visual illusion in which two patterns of circles
are presented: in one pattern, a central circle is surrounded by smaller circles whereas in
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8. the other pattern the central circle is surrounded by larger circles. The illusion is such that
the observer will most often view the central circle in the annulus of smaller circles as
bigger than the central circle in the annulus of larger circles, when in reality both central
circles are the same size.
Figure 1. The Ebbinghaus Illusion.
The hypothesis is that a colony’s nest choice process relies on comparative
heuristics such that a decision set characterized by an Ebbinghaus Effect will encourage
irrational behavior. Specifically, if a nest option were made to appear better than it is by
the presence of decoys, then it will be chosen with higher likelihood than if that same
option were made to appear worse. Whereas an absolute evaluation mechanism would
lead to choosing the maximizing option every time, a comparative heuristic might value
the target-decoy comparison at differing amounts and cause the target to be perceived as
either worth moving to or not.
In this study, the only explicit variable that was modified was the quality of nests
based on light intensity which was accomplished by light filters. The experiment involves
[8]

9. two conditions: in one condition, a colony lives in a medium-quality nest and is presented
with three other medium-quality nests for three days; afterwards, a fourth nest of high-
quality is added to the arena and the colony is given 24 hours to decide whether to move
to it or not. In the second condition, their initial home is the same, the fourth nest is still
of high-quality, but now the three decoy nests are poor-quality nests. The design of this
experiment is such that the decoy nests are only as good as (or worse than) their current
home, so the only decision in question is that of migrating to the high-quality nest.
Materials and Methods
Nest Designs.
To test for the Ebbinghaus Effect on decision making, nests were designed to
represent both an annulus of small circles in one condition and of large circles in the
other as well as a center circle to be identical in both conditions. This effect was
accomplished by using nest quality as an analogue for circle size. In this experiment, the
only attribute adjusted was interior illumination: Temnothorax prefer a darker interior
which is thought to act as an indirect cue of nest wall integrity (Franks et al. 2006).
Each nest was made from a balsa wood slat (2.4-mm thick) sandwiched between
glass microscope slides (50 × 75 mm). A circular cavity (38-mm diameter) was cut
through the middle of the slat, and an entrance tunnel was cut from the longer side (2-mm
thick). The roof was composed of two identical slides stacked on top of one another.
Interior illumination was adjusted by placing transparent neutral density filters (Rosco
Cinegel) between the roof slides. This design prevented ants from directly contacting the
filters, which can sometimes build up an electrostatic charge that the ants find repellent
[9]

10. (Sasaki and Pratt 2011). The colony’s starting nest had a rooftop with a light filter of 1
stop. The medium condition (corresponding to an annulus of large circles) was comprised
of three nests which also used 1-stop light filters. The poor condition (corresponding to
an annulus of small circles) was comprised of three nests with rooftops containing no
light filter between the glass slides. Lastly, the target nest in each condition had three 3-
stop light filters for a total of 9 stops: this acted as an analogue of the central circle in the
Ebbinghaus Illusion even though it was the darkest option (whereas in the illusion, the
central circle is the middle of three sizes).
Figure 2. Poor: 0-stop (glass); Medium: 3-stop filters; High: 9-stop filters.
Nests were illuminated at all times by two LED light fixtures suspended 1 m
above the bench on which all experiments were carried out. This provided distributed
illumination of 1900 lux in the middle to 1200 lux on the boundary (as measured by a
Lutron LX-101A light meter) which struck each arena with equal ranges and angles of
light intensity. Experiments were located on a bench within a wooden cabinet with a
heavy curtain as the fourth wall to shut out all ambient light in the room. The bench
accommodated four arenas, two of each condition, which were arranged with the
[10]

11. matching conditions positioned diagonal to each other in a square. Before each
experiment, all glass slides were washed in a commercial dishwasher, and the
experimental arena was cleaned with ethanol. Balsa slats were made fresh for each
experiment and never reused.
Figure 3. The view from the workbench with four arenas at a time, two of each condition.
Subjects.
Forty-eight colonies of T. rugatulus were used—twenty-four in each condition—
with each colony tested only once. Colonies were collected in the Pinal Mountains near
Globe, AZ (N 33° 19.00’, N 110° 52.56’, W). All colonies used had worker populations
ranging from 50 to 150 and brood populations ranging from 20 to 50. Special
consideration was given in selecting colonies with only one queen for this experiment to
eliminate any behavioral distinctions that may arise from polygyny. Each colony was
housed in a nest like those described above, but without any light filters. Each nest was
[11]

12. kept in a plastic box (11 cm × 11 cm), the walls of which were coated with Fluon to
prevent the ants from escaping. Each box was provided with a water-filled plastic tube
capped with cotton and an agar-based diet that was refreshed weekly (Bhatkar and
Whitcomb 1970). Colonies were housed in an incubator with a 12 hour day-night cycle
(with temperatures ranging from 15°C at night to 22°C during the day).
Experimental Procedure.
Initially, in each condition, a starting nest of medium quality was placed in a
circular arena 25 cm in diameter with Fluon-coated walls. This starting nest was on the
edge of the circle with the entrance facing towards the center and with a water tube
positioned lengthwise behind it. Also, the arena was oriented on the bench such that the
nest was on the periphery of the illuminated area, therefore exposed to the least amount
of light of any location in the arena. The particular positioning of the starter nest on the
bench and of the water tube in the arena was implemented to augment the value of the
starter nest, creating extra incentive to not move from that nest (because it is adequately
dark and close to water).
The colony’s home nest was placed 2 cm across from this nest and the roof was
removed from the home nest to induce migration to the starter nest. After 24 hours, when
the colony had successfully migrated, the remnants of their old home were removed. At
the same time, three new nests were introduced: one at the opposite edge across from the
starter nest and two below that, rotated 90° to have entrance sides facing each other. In
the medium condition, these three nests were of medium quality (identical to the starter
nest), whereas in the poor condition the three nests had no light filter. The colony was
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13. then allotted 72 h to become familiar with the three nest options, none of which
dominated their current situation on level of light or proximity to water.
At the end of this period of exploration, a target nest of the same high quality in
each condition was placed equidistance between the three decoy nests with its entrance
facing the starter nest. Lastly, the colony was given 24 h of exposure to the high quality
target nest in the presence of the three other alternatives as well. In this case, the colony
was not induced to move at any point but rather given the option to relocate. The
colony’s choice data were collected by recording whether or not the colony moved to the
high-quality nest as observed on the end of the 5th
day.
Figure 4. The six-day progression shown for the Poor Condition. Days 1 through 5
represent full 24-hour days; Day 6 represents the final moment of observation
The presence of an Ebbinghaus Effect was tested with a χ2
test of independence.
The null hypothesis was that the preference for moving to the high-quality nest was
independent of the presence of the strictly-dominated surrounding nests. The alternative
hypothesis used was that the presence of poor-quality decoys would drive preference
Day 1 Day 2 Day 5 Day 6...
...
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14. towards the high-quality nest with a higher frequency than would the presence of
medium-quality decoys.
Results
According to the experimental design, only one variable was observed and
recorded as the rest were controlled to be reasonably non-confounding. Out of 48
colonies total, 20 moved to the high-quality nest on the fifth day and 28 did not move to
that nest. This comparison acts as the conditional standard for the Chi-Squared test for
how likely a colony is to move to the high-quality nest regardless of where it starts. To
test for independence against that standard, the movement decisions are compared
between conditions.
In the medium condition, 6 colonies moved to the high-quality nest and 18 did
not. However, the poor condition yielded movement to the high-quality nest by 14
colonies and the absence of movement by the remaining 10 colonies. A Chi-Squared test
on these data leads to a value of 5.48 with a p-value of less than 0.05 (χ2
= 5.48, df = 1, N
= 48, P < 0.05). In words, at a level that is statistically significant, a colony’s decision to
move to the high-quality nest is not independent of whether it is surrounded by medium-
quality nests versus poor-quality nests. Therefore, the presence of different unattractive
non-target nests had an effect on the likelihood that a colony would move to an
undeniably superior nest.
Table 1. Nest Quality refers to the quality of the three non-target nests. The results displayed in a
contingency table. Chi-Square Test of Independence: (χ2= 5.48, df = 1, N = 48, P < 0.05).
[14]

15. These results report every final movement decision, but throughout the trials there
were three colonies which presented anomalies. In two cases, a colony (one in each
condition) migrated to a non-target nest within the three day exploration period and failed
to move to the high-quality nest by the end of the experiment; these were both recorded
as having not moved. In the third case, a colony in the poor condition migrated to a poor-
quality nest after two days of exposure but then ultimately moved to the high-quality nest
by the conclusion of the trial; this colony was recorded as having moved. Even if these
data are rejected, the effect still exists and is statistically significant at the 0.05 level.
Nest Quality
Poor
Condition
Medium
Condition
Decision
Moved
14 6
Not
Moved 10 18
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16. Conclusions
The initial hypothesis was confirmed in the context of this Ebbinghaus Illusion
analogue. Evidence from this experiment shows that ant colonies as decision-makers are
prone to systematic irrationality—plausible fitness-maximizing errors. In particular, the
colonies exhibited susceptibility on account of comparative evaluation to a form of the
decoy effect cognitive bias as studied in human subjects. However, past thorough
research has concluded that colonies can effectively protect themselves from the decoy
effect even if the choices of individuals are biased (Sasaki and Pratt 2011). As group
rationality emerged from individual irrationality, Sasaki and Pratt found that nest-site
preference by colonies was not affected when presented with a typical decoy effect
scenario. In this case, two targets were designed to be equally preferred, and the colonies’
choices remained to be almost equally distributed between the two even in the presence
of an asymmetrically dominated decoy. In contrast, the current study’s results show an
evident shift in preferences (between the two conditions) and in the case of strictly-
dominated decoys. The difference in these results speaks to the differences in what was
being asked of the ants as decision-makers.
Another similar study offers further confounding evidence that might have
encouraged the inverse of the initial hypothesis. An experiment by Healey and Pratt
subjected colonies to living in a series of several identical-quality nests (in two
conditions: poor-quality nests or high-quality nests) for a number of weeks. After this
period of exposure, colonies were presented with a medium-quality nest and their home
was destroyed. The time that elapsed for migration to the new nest was recorded and
viewed as an indication of the effect of previous experience on preference for the
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17. medium-quality nest. In seeming contrast to the current study’s results, the researchers
found that colonies with recent experience of high-quality nests moved more quickly to
the medium-quality nest than did those with recent experience of poor-quality nests
(Healey and Pratt 2008). This result was a surprise even to them, and its conflicting
results can likely be explained by two major aspects: the ants experienced state changes
considering they were induced to move by the destruction of their home and, similarly,
time-to-move in this situation is not a perfect representation of preferences.
There are two ways to interpret the investigated Ebbinghaus Effect on the ants’
behavior: informally, an internal or external interpretation. The internal interpretation
ascribes the inter-condition preference shift to a change in internal selectivity. In theory,
prior experience could alter selectivity in such a way as to redefine a colony’s searching
and discrimination strategy. Past research focused on this phenomenon has shown that
context-dependent selectivity modifications offer a reasonable explanation for some
choice patterns (Sasaki and Pratt 2013). Specifically, selectivity changes manifest in
reaction to a meaningful distribution in the quality of available alternatives (Real 1990).
Applied to the experimental paradigm, it would be as though the colonies which were
presented with a period of poor-quality nests in turn set a more liberal acceptance
threshold whereas the colonies which were presented with a period of high-quality nests
set a more conservative acceptance threshold. This internal change can be attributed to a
mechanism like the scarcity heuristic: overvaluing or undervaluing the high-quality
nest—beyond attribute quality—when viewed in the context of “a world of poor nests (or
medium nests),” based on the perceived physical and temporal scarcity of it. With this
[17]

18. interpretation, the prevailing decisions in both conditions validate these ants’ ability to
adhere to ecologically rational decision-making.
Colonies in the poor condition actually did find themselves in a world of poor
nests, so their shift in selectivity motivated them to move to a rare high-quality nest—
with a sense of urgency—which they concluded may not be available forever: they made
the best decision they could with the information available. On the other hand, colonies in
the medium condition viewed the high-quality nest in the context of their world in which
similar nests might not be so hard to come by; they assessed the nest as neither physically
nor temporally scarce. These colonies understood moving as an unnecessary cost for a
subpar benefit given the world they lived in. This interpretation assumes that the colonies
in the poor condition were right to think that the high-quality nest was scarce and that the
colonies in the medium condition were right to think that the high-quality nest was not
scarce; the result could be considered context-dependent ecological rationality.
On the other hand, the external perspective points towards comparative evaluation
and reinforces the prospect of its existence in various facets of animal decision-making.
This satisfies both the motivation and results of the hypothesis; these ant colonies employ
a comparative evaluation heuristic when house hunting which may or may not uphold
ecological rationality. In the framework of this experiment, comparative evaluation took
place as the colonies discovered the quality of the non-target nests and subsequently
compared the high-quality nest to those nests. The ants made side-by-side comparisons of
the high-quality nest and non-target nests and ultimately made a decision dependent not
only on whether the former was better but also on the differential of how much better.
Past research has shown that this mechanism of evaluation is at least physiologically
[18]

19. possible; specifically, these ants are capable of retaining memories of nest qualities
observed while scouting (Stroeymeyt et al. 2011).
According to the results, ecological irrationality via comparative evaluation could
be exemplified in one of two ways: by colonies in the medium condition or colonies in
the poor condition. If the original assumption holds, that moving to the high-quality nest
is the fitness-maximizing choice, then the majority of colonies in the medium condition
(75%) acted ecologically irrational by forgoing that choice. That is, the comparison of the
high-quality nest to medium-quality nests did not present a sufficiently attractive
difference of quality. On the other hand, if the decision to move from the medium-quality
nest to the high-quality nest is thought of as generally not a net gain in benefits (dark
interior, structural integrity) over costs (emigration, distance from water), then, contrary
to initial assumptions, the fitness-maximizing decision would instead be to not move to
the superior nest. In that case, the majority of colonies in the poor condition (58%)
demonstrated ecologically irrational behavior by moving to the high-quality nest on
account of comparative evaluation. Of course, this can only be concluded on the basis
that the experimental design was representative of the ants’ natural environment to the
point that the ants were expected to behave exactly as they would if they had encountered
a similar scenario in nature.
In contrast, just as a scarcity heuristic would be responsible for encouraging the
colonies to value perceived-to-be rare good nests more highly than perceived-to-be
common good nests, a comparative heuristic would have the same effect (as shown in
this experiment). If this would lead to fitness-maximizing decisions in their natural
environment—because a high-quality nest might actually be rare among a majority of
[19]

20. inferior nests—then comparative evaluation in similar nest-site choice scenarios
effectively leads to ecological rationality. Therefore, careful analysis would have it that
ecological rationality also follows from the external interpretation.
In order to gain insight on whether the results can be attributed to an external or
internal element, further research could be conducted. Specifically, the research would
include an identical experimental design with one informative difference. Instead of
presenting the colonies the choice between four concurrent nest alternatives at the finale,
the three non-target nests should be removed upon the introduction of the high-quality
target. This alteration would provide a distinction between internal selectivity changes
and external comparative evaluation based on the results. Without nests to compare with
side-by-side, the colonies would behave in one of two ways: they may exhibit equal
preferences across conditions because they would be judging the nest without the context
of decoys. This result would support the hypothesis predicting comparative evaluation
(the existence of which was found in the current study to produce ecological irrationality)
because the absence of comparisons led to the absence of an effect. Alternatively, the
colonies may display the same difference in preferences between conditions as found
from the current research. This outcome would support the internal interpretation in that
the colonies were influenced by prior exposure which formed internal selectivity shifts
which dictated their final decisions.
In conclusion, the research supports a descriptive explanation for the existence of
these ants’ decision rule for nest-site choice, comparative evaluation, which is likely to be
fitness-maximizing in their natural environment.
[20]

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