1. Defining Habituation using Hand Geometry
Eric P. Kukula' Stephen J Elliott, Ph.D.2
Industrial Technology, Purdue University Industrial Technology, Purdue University
West Lafayette, Indiana USA West Lafayette, Indiana USA
kukulagpurdue.edu elliottgpurdue.edu
Bryan P. Gresock3 Nathan W. Dunning4
Industrial Technology, Purdue University Computer Technology, Purdue University
West Lafayette, Indiana USA West Lafayette, Indiana USA
Abstract-The word "habituation" has many meanings within the device or any other biometric to the general population,
biometric community. Most people define the concept of training of the device's users is very important.
habituation as "continued use of a biometric device." When a
user is habituated, he or she is capable of providing repeatable Each biometric modality has specific interaction issues that
samples to the biometric sensor, and the performance scores of need to be resolved through training. For hand geometry
the biometric sensor, relative to that user, have stabilized. This readers, training must emphasize hand placement because hand
paper establishes a model of the processes of habituation and placement is a key component to successful use. Since hand
provides score data from hand geometry to show how this geometry is dependent on orientation of a user's hand, most
concept works with actual data. We illustrate a four-step process hand readers have pins to facilitate the process of orienting the
of a user's interaction with the device and describe how the data user's hand for correct alignment. Training must address how
seems to prove that an individual becomes fully habituated after users should interact with the alignment pins. If the user does
repeated use of the device. The type and amount of user training, not perform hand placement correctly, interaction will be
and number of interaction attempts are shown to have an impact problematic and a higher than normal matching score will
on the biometric sensor's performance scores. result. A higher matched score could lead to false rejections
(FRRs) [2]. With any technology-based system, training is
Keywords- biometrics, hand geometry, habituation, human- essential for the ongoing successful use and integration of the
technology. Understanding how users' habituation and
acclimation relates to the successful use of hand readers will
I. INTRODUCTION establish the appropriate training period that customers of a
How an individual interacts with a biometric device so as to particular type of biometric systems can anticipate.
make consistent, repeatable presentations is an important topic
of discussion within the biometrics community. In this paper, ii. HABITUATION AND ACCLIMATION
we propose a novel process to define habituation and provide
data on how quickly individuals in different circumstances can The definition of habituation varies, depending on context.
fully habituate. For this experiment, we use a hand geometry [4] notes two recurring characteristics for acclimation and
device. habituation. First, acclimation is the process in which a user of
a biometric system adapts his or her techniques to achieve a
Hand geometry has been utilized commercially for more proper match of his or her biometric template. Second,
than three decades [1]. The first hand geometry readers were habituation may be partial or full (complete). Partial
used in government facilities to provide high-level security habituation is the period of time during which no new
access to settings such as nuclear power plants [2]. Hand adaptation techniques are used to achieve a successful match to
geometry readers are becoming increasingly ubiquitous; today, the biometric template. Full habituation occurs when a user
they can be found in public applications ranging from hotels, matches his or her biometric template using subconscious
college dormitories, and manufacturing plants to parking lots; techniques. Becoming fully habituated to a biometric system is
they support access control, as well as time and attendance a four-step process, as shown in Figure 1. In the first step, a
tracking [3]. user is introduced to the equipment for the first time. Note that
Hand geometry measures the size and shape of the human the four "steps" are not discrete, but rather are continuous;
hand [3]. When an individual places his or her hand on a overlaps between the steps will occur.
reflective platen and makes contact with the alignment pin, a
picture of the hand is taken. When deploying a hand geometry
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2. Userintroduced to hiQmebics stemorntfirstte. During week 7, participants in group 3 enrolled in the reader
and were required to provide three scores under thirty.
cclimation: User adapts his techniques to
tytaErnxnachanrnn rna Toldwhato. Group 4 enrolled in the hand geometryieader
drru ngweek
E
achievepropermatchofbiometrictemplate.
r t Self Teaching - 2 of the experiment; participants in this group revisited every
ChlangtingoneDas
Changing rAy
to s
[llif
behavior Changingtosurvive[s] Self techniquestousethe week and made one verification attempt, mimicking
A d ti tW a What arethe differentw
Teaching device?
A
device?
l
typical
a
access control application. There were no scoring constraints
for group 4 during weeks 2, 4, or 6.
_s__t___I_Ch_r_____ks Partial Habituation: Nomatch adaptation nechrique you wantto repeat.T P q p p gr p | The rotocol required all articipants
new of biometric of Pickthetechnique inoupsto
all
fbru-itmpwohansdt detalused
Nbriasbc ative learnglevel
tat albsh
daiy
sfeub-c onscience to be used template
echnique to achieve proper
template.Selection - l perform three consecutive verification attempts with scores
characte6fstics: resulting in a reduced numbera oferrors and number encel
Reducedresponsvenessto ovne under thirty during week 7 (the experiment's final week),
as
experence [3] ofaftemptstoaftainalevelofpetformance.
Reducedl resptbnsiVeness to given
a
I
L D
~~~~~~~~~~~~~~~~~~~~Learn the selected u*
this was a strict threshold level. The four groupsconducted
HabituatiprcessWorksits Repeated technique. verification attempts until each participant successfully
theconSCicus[5]
L ak of sponse[2] Full Habituation: User matches biometric aet
chieved three scores under thirty to establish whether there
P
'Nop out habituatoour
assbdiativb learning [8]
template by subcoscious techiques. was a statistically significant dIfference among groups
With
observations[8]
n ndvou
prebocupiewth nsignificarit
Fuhe rdciono repniveest
dbel
a ove thets
Pefr
expenence. Users require minimal concentration and
no/minimal errors producinga tighter dissibutionof
withoutonnsciPerForm
S ubwihthlous t cought.
use weeks.
thought
thetaskl7
subjected to different levels of training over the previous six
scores, minutiae, etc...
Figure 1. Conceptual model of habituation/acclimation for biometrics A. Experimental Setup
Testing involved two commercially available hand
geometry readers (see Figure 3) situated on a desk at an
III. METHODOLOGY elevation of twenty-nine inches from the floor. Participants
The motivation for this study is to more fully understand performed the test while seated in a chair to exclude the
the appropriate level of training required to achieve repeatable potential influence of extraneous factors such as variations of
performance. The hypothesis was to examine the hand the participants' heights.
geometry scores from four groups of participants who
interacted with the device in different scenarios. Figure 2
shows the experimental design ofthe four groups.
Group 1 enrolled during the first week of the seven-week
study and performed verification attempts during each week of
data collection until they achieved three consecutive scores
under the threshold of thirty.
Group 2 simulated the recommendations from the
InterNational Committee for Information Technology
Standards (INCITS) M1.5 draft standard (1602D-5): members
of group 2 utilized six-week intervals between revisits. In this Figure 3. Schlage Recognition Systems Handkey IIR
scenario, during week 1 and week 7, group 2 participants were
required to provide three consecutive scores under the
threshold of thirty. B. Enrollment
Enrollment is the process of collecting a biometric sample
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 in this case, hand geometry from a person. The data from
8/21 8/28 914 9111 9/18 9/25 1012 the sample is processed and stored in a database as a template
for subsequent usage to validate an individual's identity. Prior
Group I Enol to this study, study participants had no experience with a hand
er X ~~~~~~~~~~3
3 3 ~ ~ ~ ~ 3- 3
under30. under30. unde 30 30. 3 geometry reader, and were neither habituated nor acclimated.
Group 2
Enroll
3
~~~~~~~~~Four
groups were created and each group was enrolled at
different periods over the course of the study.
When seated, participants were provided with instructions
Enol on how to use the device and a brief demonstration on the
Group 3 proper technique for hand placement A test administrator was
present to ensure each test participant followed the test protocol
Enrollfor enrollment. Upon completion in the participant's unique
of the demonstration and
Group 4 1 A At1 3 Group training, the administrator entered
code and the participant placed his or her dominant hand onto
Figure 2. Experimental design of the four groups the platen of the hand geometry reader, applied pressure to the
pins, and kept the hand in position until the test administrator
Group 3 served as our control group; they did not interact instructed the participant to to remove the hand from the
with the hand geometry reader until week 7 (the final week). reader. Participants were provided with visual cues (in the form
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3. of LEDs) to facilitate correct hand placement in the hand 10o Week I Group I Attempts vs. Score
reader. When the LEDs on the hand reader are extinguished, 90-
then the participant has achieved proper pin / finger placement. 80-
Enrollment consisted of three hand placements to create a 70Q
unique template for each test participant. In some cases, the
device may have required additional hand placements if the 40 ' .
first three did not satisfy the enrollment criteria. 3- =
C. Verification
Verification is the process of matching a claimed identity to 4 C. 7 9 I 12 13 14
a biometric characteristic or sample. The hand geometry unit
used in this study functions as a one-to-one (verification) -Wek 2 Group I - Attempts vs. Score
system. During each verification attempt, the test participant
entered the unique four-digit number provided during
enrollment and, aided by visual cues from the hand geometry
system, placed his or her hand on the platen around the guide
pins, as had been instructed and demonstrated during the 40
enrollment stage. 3l
IV. RESULTS { M
Central to this paper is the definition of habituation and 1 2
3 4 5 6 7 a
910 1 13 l
examination of the amount of interaction required to achieve Week 4 Group I - Attempts vs. Score
that status. The study endeavors to answer to research question, 90
"What is the appropriate level of training and interaction Ho
required to achieve repeatable performance?" The statistical 7-
analysis investigated two variables across the groups: number 60
of attempts and the match score output from the hand geometry
device. 30
Before further analysis, tests for violation of the assumption -
of normality were performed. The results of the normality tests
showed the match score data was normally distributed, but the 4................ 14
attempt data was not. Since each group had a defined level of
interaction, the number of attempts were similar within each of 1X=Week roupi - Attempts vs Score
the groups, causing the distribution of attempts to be 901
multimodal and thus non-normal. 81
0
701
601
A. Group I Results 50
Group 1 enrolled during week 1 of the study and performed 41
verification attempts during each week of data collection until*
each member of the group receiving three consecutive scores
under the threshold of thirty. The model assumed that the ID
process would fully habituate the group's participants. 4 6 7 9 1o I 12 3 4
Examining group 1 scores and attempts by the participants over
seven weeks yielded a drop in the scores, but the change was 0 Week 7 Groupi I Attempts vs Sore0
not statistically significant. The visual representation of these 90
results (see Figure 4) shows the process of acclimation and
habituation occurring over the seven-week period. The
university's academic calendar precluded collection of data
during weeks 3 and 5. It is interesting to note that, after week 3, 4t
participants regressed in performance, whereas after the week 5 30|
break, the participants varied less as a group. Examination of 20 .
the week 7 chart shows that most participants are habituated to -
the device; they required minimal attempts to perform three
consecutive scores under thethresholdofthirtv. The data also3
consecutive
under the threshold of thirty. The data also 4 5 6 7 8 9 to I 1. 4S i 14
reveals decreases as the mean number of attempts by week Figure 4. Group 1 time series plot of attempts vs. scores reveal partial
decreased, as well as the median, standard deviation, and habituation
variance (see Table 1).
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4. TABLE I. ANALYSIS OF NUMBER OF ATTEMPTS, GROUP 1 attempt in weeks 2, 4, and 6 no real analyses could be
performed. However at week 7, this group had the lowest range
1
Wcc1 M2n
5.267
M4
4
n 3Std D10iati9n
3.24
Varianc
10.495
and mean score, as shown in Figure 6.
2 4.8 5 1.612 2.6 E. All Groups Combined
4 44.667 4 2.41 5.81
6 4.133
4.133 3
3 1.552
1.552 2.41
2.41.'
In order to consider the groups together, a one-way analysis
3933 1 438 2 067 Iof variance (ANOVA) was performed to examine the average
7 3.933 3 1.438 2.067 score of the four groups during week 7 (see Figure 6). This
ANOVA revealed significant differences between the four
B. Group 2 Results groups: F (3,253) = 4.58 and p < 0.004 (see Table 2). The
results reveal that participants in groups 1 and 4 have the
Group 2 enrolled in week 1 ofthe study and then completed lowest mean scores and the least amount of variation in scores
three verification scores under thirty. After six weeks, the
participants returned and again attempted to complete three in week 7. Interpreting the results, participants in groups 1 and
verifications with scores under thirty. The mean number of 4 progressed towards full habituation, which is illustrated in
attempts was 4.71 for week 1 and 5.21 for week 7 Figure 6, the plot of the match scores.
There was no statistically significant difference between the 100-
attempts on week 1 and week 7. The graphical summary for all
participants is shown in Figure 5. It is apparent that the process go
of habituation does not occur and participants perform no better
in week 7 than they did in weekl. 60
60-
1to WeeIk I Group 2 - Attempts vs. ==
Stoe
90- < 40-
'70)
60- 20 ~
30 S, V A 7 0
I 2 3 4
IWIf- ,._, .- roup
0-
IFigure 6. Week 7 match scores, by group
3 2 3 4 5 6 7 9 9 10 II I2 iS3 14
I. Wee1 7 Group 2 _ Atte mptsJ vs. Score
tk TABLE II. MEANS AND STANDARD DEVIATIONS, ANOVA OF WEEK 7
9',90*1 # A SCORES ACROSS GROUPS
So 01
Group N (Attcmpts) t IISD
601 .,
N *I fS:R 1 ~~~~~~1
~ _____53_____ _ 1 18.66 1 13.22
40i 2 73 27.38 17.96
m.
v ,kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkrkkkkkkkki
'kkkkkkI8 .8 %.6 if2
4 44 18.3 10.5
1 2 3 4 5 6 7 9 t 1t ' 12 13 X4 The second analysis examined the difference in
Figure 5. Group 2 time series plot of attempts vs. scores reveal no performance of groups 1 and 2 during week 1 (the first week of
acclimation or habituation the study) and week 7 (the last week of the study). A one-way
ANOVA analyzed the average score of groups 1 and 2 during
C. Group 3 Results week 1, which revealed no statistically significant difference
between the two groups: F (1, 133) = 0.10 and p=O.747, which
Group 3 enrolled and verified three times in the last week would be expected, since both groups received the same
of the study. There should have been no difference between treatment. However, when this analysis was repeated on the
group 3 scores in week 7 and those of the other groups during data gathered six weeks later, the results were quite different.
their respective enrollment weeks. As expected, there was no The ANOVA revealed a statistically significant difference in
statistically significant difference between the groups. the mean scores between groups 1 and 2: F (1, 124)= 8.97 and
Nonetheless, it is interesting to note that the range of matching p=0.003. Table 3 lists the means and standard deviations for
scores for group 3 was greater than the other groups. week 1 and week 7 analyses. Figures 7 and 8 show the
graphical representation of these analyses. Refer to Figures 4
D. Group 4 Results and 5 to assess the relationship between attempts and scores of
This group mimicked the access control environment of one the two groups in weeks 1 and 7.
attempt each week. As these participants only conducted 1
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5. TABLE III. MEANS AND STANDARD DEVIATIONS, WEEK 1 AND WEEK 7 thirty), and the ranges of these groups were smaller than those
SCORES FOR GROUPS 1 AND 2 of groups 2 and 3. Therefore, when considering habituation of a
hand geometry reader, it is important to recognize that the type
Week Group N (Attcmpts) ll SD and number of training attempts and interaction will affect the
1 1 69 21.07 13.47 score. This factor is crucial to practitioners implementing
biometric solutions in their organizations, as the cost for
2
1F 66 21 l.85
2 14.43 training and instruction is high.
7 1 53 18.66 13.22
2 73 27.38 17.96 VI. FUTURE WORK
While this paper provides a conceptual framework for
defining habituation and provides data that shows the process
70- of habituation, there are other factors that can have an effect on
habituation. The authors believe training might affect whether,
60- . when, and how long it takes to achieve habituation. Therefore,
50; *instead ofbe interestingnumber of interactions,experiment that,
it would varying the to conduct a similar varies the type
t 40 0 t *= =and amount of training a participant receives before enrollment
=X
*s==**
0% to determine whether the type of training, (i.e., no training;
i30- visual instruction; oral instruction; and a combination of oral
and visual instruction with and hands-on experience) changes
20. _ - - the progress toward habituation and acclimation.
10 4
3 . ' = VII. g
,, REFERENCES
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G
2
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Figure 7. Plot of match score for groups 1 and 2 for week 1 28, 1999.
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[9.] Thehttp://www.thefreedictionary.com/habituation.
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parntuardic
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n
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e ased on
.
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"Aciato, from
fro http://medical-
htp/eicl
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the performance success of participants .relative to the device.*
. . . .10.] ~~~~~Wikipedia.ic"Acclimation,"
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