(2007) Defining Habituation Using Hand Geometry

Defining Habituation using Hand Geometry

Eric P. Kukula' Stephen J Elliott, Ph.D.2Industrial Technology, Purdue University Industrial Technology, Purdue University

West Lafayette, Indiana USA West Lafayette, Indiana USAkukulagpurdue.edu elliottgpurdue.edu

Bryan P. Gresock3 Nathan W. Dunning4Industrial 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 auser is habituated, he or she is capable of providing repeatable Each biometric modality has specific interaction issues thatsamples to the biometric sensor, and the performance scores of need to be resolved through training. For hand geometrythe biometric sensor, relative to that user, have stabilized. This readers, training must emphasize hand placement because handpaper establishes a model of the processes of habituation and placement is a key component to successful use. Since handprovides score data from hand geometry to show how this geometry is dependent on orientation of a user's hand, mostconcept works with actual data. We illustrate a four-step process hand readers have pins to facilitate the process of orienting theof a user's interaction with the device and describe how the data user's hand for correct alignment. Training must address howseems to prove that an individual becomes fully habituated after users should interact with the alignment pins. If the user doesrepeated use of the device. The type and amount of user training, not perform hand placement correctly, interaction will beand number of interaction attempts are shown to have an impact problematic and a higher than normal matching score willon the biometric sensor's performance scores. result. A higher matched score could lead to false rejections

(FRRs) [2]. With any technology-based system, training isKeywords- biometrics, hand geometry, habituation, human- essential for the ongoing successful use and integration of the

technology. Understanding how users' habituation andacclimation relates to the successful use of hand readers will

I. INTRODUCTION establish the appropriate training period that customers of aHow an individual interacts with a biometric device so as to particular type of biometric systems can anticipate.

make consistent, repeatable presentations is an important topicof discussion within the biometrics community. In this paper, ii. HABITUATION AND ACCLIMATIONwe propose a novel process to define habituation and providedata 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 anddevice. habituation. First, acclimation is the process in which a user of

a biometric system adapts his or her techniques to achieve aHand 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). Partialused in government facilities to provide high-level security habituation is the period of time during which no newaccess to settings such as nuclear power plants [2]. Hand adaptation techniques are used to achieve a successful match togeometry readers are becoming increasingly ubiquitous; today, the biometric template. Full habituation occurs when a userthey can be found in public applications ranging from hotels, matches his or her biometric template using subconsciouscollege dormitories, and manufacturing plants to parking lots; techniques. Becoming fully habituated to a biometric system isthey support access control, as well as time and attendance a four-step process, as shown in Figure 1. In the first step, atracking [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, apicture of the hand is taken. When deploying a hand geometry

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Userintroduced to hiQmebics stemorntfirstte. During week 7, participants in group 3 enrolled in the readerand were required to provide three scores under thirty.

E cclimation: User adapts his techniques totytaErnxnachanrnn achievepropermatchofbiometrictemplate.rna Toldwhato. Group 4 enrolled in the hand geometryreaderduringweek

r t Self Teaching - 2 of the experiment; participants in this group revisited everyA d ti tW a What arethe differentwChlangtingoneDas behavior [llif techniquestousethe week and made one verification attempt, mimickingatypical

Changing to s rAy Self device?AChangingtosurvive[s] Teaching device? l access control application. There were no scoring constraintsfor group 4 during weeks 2, 4, or 6.

_s__t___I_Ch_r_____ks Partial Habituation: No newadaptation of Pickthetechnique | The rotocol required all articipantsinalloupstoNbriasbcative learnglevel echnique to achieve proper match of biometric nechrique you wantto repeat.T P q p p gr p

tatalbshsfeub-c onscience to be used template.Selection -fbru-itmpwohansdtdaiydetalused template \l perform three consecutive verification attempts with scorescharacte6fstics: Reducedresponsvenessto a ovne encel under thirty during week 7 (the experiment's finalweek),as

Reducedl resptbnsiVeness to a given resulting in a reduced number oferrors and numberexperence[3] ofaftemptstoaftainalevelofpetformance.L D this was a strict threshold level. The four groupsconductedI ~~~~~~~~~~~~~~~~~~~~Learnthe selected u*

HabituatiprcessWorksits Repeated technique. verification attempts until each participant successfullytheconSCicus[5] chieved three scores under thirty to establish whether thereLak of sponse[2] Full Habituation: User matches biometric aetP template by subcoscioustechiques. was a statistically significant dIfference among groups'Nopassbdiativb learning[8]

Fuhe rdciono repniveest a ovePefr thetsWith out habituatoour nndvou dbel withoutonnsciPerForm thetaskl7subjected to different levels of training over the previous sixprebocupiewth nsignificarit expenence. Users require minimal concentration and S ubwihthlous t cought.observations[8] no/minimal errors producinga tighter dissibutionof use thoughtweeks.

scores, minutiae, etc...

Figure 1. Conceptual model of habituation/acclimation for biometrics A. Experimental SetupTesting involved two commercially available hand

geometry readers (see Figure 3) situated on a desk at anIII. 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 thethe appropriate level of training required to achieve repeatable potential influence of extraneous factors such as variations ofperformance. The hypothesis was to examine the hand the participants' heights.geometry scores from four groups of participants whointeracted with the device in different scenarios. Figure 2shows the experimental design ofthe four groups.

Group 1 enrolled during the first week of the seven-weekstudy and performed verification attempts during each week ofdata collection until they achieved three consecutive scoresunder the threshold of thirty.

Group 2 simulated the recommendations from theInterNational Committee for Information TechnologyStandards (INCITS) M1.5 draft standard (1602D-5): membersof group 2 utilized six-week intervals between revisits. In this Figure 3. Schlage Recognition Systems Handkey IIRscenario, during week 1 and week 7, group 2 participants wererequired to provide three consecutive scores under thethreshold of thirty. B. Enrollment

Enrollment is the process of collecting a biometric sampleWeek 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 in this case, hand geometry from a person. The data from8/21 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. PriorGroup I Enol to this study, study participants had no experience with a hand3 3 ~ ~ ~ ~ ~~~~~~~~~~333-

\under30. under30. unde 30 er 30.X 3 geometry reader, and were neither habituated nor acclimated.

Enroll ~~~~~~~~~Fourgroups were created and each group was enrolled atGroup 2 3 different periods over the course of the study.

When seated, participants were provided with instructionsEnol on how to use the device and a brief demonstration on the

Group 3 proper technique for hand placement A test administrator waspresent to ensure each test participant followed the test protocol

Group

Enrollfor enrollment. Upon completion of the demonstration andGroup 4 1 A At1 3 training, the administrator entered in the participant's uniquecode 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 thepins, 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 thewith the hand geometry reader until week 7 (the final week). reader. Participants were provided with visual cues (in the form

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of LEDs) to facilitate correct hand placement in the hand 10o Week I Group I Attempts vs. Scorereader. When the LEDs on the hand reader are extinguished, 90-then the participant has achieved proper pin / finger placement. 80-

70QEnrollment consisted of three hand placements to create aunique template for each test participant. In some cases, thedevice may have required additional hand placements if the 40 ' .first three did not satisfy the enrollment criteria. 3- =

C. VerificationVerification is the process ofmatching a claimed identity to 4 C. 7 9 I 12 13 14

a biometric characteristic or sample. The hand geometry unitused in this study functions as a one-to-one (verification) -Wek 2 Group I - Attempts vs. Scoresystem. During each verification attempt, the test participantentered the unique four-digit number provided duringenrollment and, aided by visual cues from the hand geometrysystem, placed his or her hand on the platen around the guidepins, as had been instructed and demonstrated during the

40enrollment stage. 3l

IV. RESULTS { MCentral to this paper is the definition of habituation and 1 2 3 4 5 6 7 a 9 10 1 13 l

examination of the amount of interaction required to achieve Week 4 Group I - Attempts vs. Scorethat status. The study endeavors to answer to research question, 90

"What is the appropriate level of training and interaction Horequired to achieve repeatable performance?" The statistical 7-

analysis investigated two variables across the groups: number 60of attempts and the match score output from the hand geometrydevice. 30

Before further analysis, tests for violation of the assumption -of normality were performed. The results of the normality testsshowed the match score data was normally distributed, but the 4................ 14attempt data was not. Since each group had a defined level ofinteraction, the number of attempts were similar within each of 1X=Week roupi - Attempts vs Scorethe groups, causing the distribution of attempts to be 901multimodal and thus non-normal. 810

701601

A. Group I Results 50

Group 1 enrolled during week 1 of the study and performed 41verification attempts during each week of data collection until*each member of the group receiving three consecutive scoresunder 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 4Examining group 1 scores and attempts by the participants overseven weeks yielded a drop in the scores, but the change was 0 Week 7 Groupi I Attempts vs Sore0not statistically significant. The visual representation of these 90results (see Figure 4) shows the process of acclimation andhabituation occurring over the seven-week period. Theuniversity's academic calendar precluded collection of dataduring 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 threeconsecutive under thethresholdofthirtv. The data also3 4 5 6 7 8 9 to I 1. 4S i 14consecutive scores under the threshold of thirty. The data alsoreveals decreases as the mean number of attempts by week Figure 4. Group 1 time series plot of attempts vs. scores reveal partialdecreased, as well as the median, standard deviation, and habituationvariance (see Table 1).

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TABLE I. ANALYSIS OF NUMBER OF ATTEMPTS, GROUP 1 attempt in weeks 2, 4, and 6 no real analyses could beperformed. However at week 7, this group had the lowest range

Wcc1 M2n M4 n 3Std D10iati9nVarianc and mean score, as shown in Figure 6.1 5.267 4 3.24 10.4952 4.8 5 1.612 2.6 E. All Groups Combined4 4.667 4 2.41 5.814

4.133 3 1.552 2.41 In order to consider the groups together, a one-way analysis6 4.133 3 1.552 2.41.'3933 1 438 2 067 Iof variance (ANOVA) was performed to examine the average7 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 fourB. 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 theGroup 2 enrolled in week 1 ofthe study and then completed lowest mean scores and the least amount of variation in scoresthree verification scores under thirty. After six weeks, theparticipants returned and again attempted to complete three in week 7. Interpreting the results, participants in groups 1 andverifications with scores under thirty. The mean number of 4 progressed towards full habituation, which is illustrated inattempts 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 allparticipants is shown in Figure 5. It is apparent that the process goof habituation does not occur and participants perform no betterin 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 4IWIf- ,._, .- roup0 - IFigure 6. Week 7 match scores, by group

3 2 3 4 5 6 7 9 9 10 I I I 2 iS3 14

I. Wee1tk 7 Group 2 _ AttemptsJ vs. Score TABLE II. MEANS AND STANDARD DEVIATIONS, ANOVA OF WEEK 790*1 A9', # \ SCORES ACROSS GROUPS

So 01

Group N (Attcmpts) t IISD601 .,

*I f :RSN 1 ~~~~~~~1_____53_____ _ 1 18.66 1 13.2240i 2 73 27.38 17.96

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4 44 18.3 10.5

1 2 3 4 5 6 7 t9 1t ' 1 2 13 X 4 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 ofacclimation 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 duringC. Group 3 Results week 1, which revealed no statistically significant difference

between the two groups: F (1, 133) = 0.10 and p=O.747, whichGroup 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 thegroup 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 instatistically significant difference between the groups. the mean scores between groups 1 and 2: F (1, 124)= 8.97 andNonetheless, it is interesting to note that the range of matching p=0.003. Table 3 lists the means and standard deviations forscores 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 4D. 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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TABLE III. MEANS AND STANDARD DEVIATIONS, WEEK 1 AND WEEK 7 thirty), and the ranges of these groups were smaller than thoseSCORES 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 typeWeek 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 implementingbiometric solutions in their organizations, as the cost forF12 66 212 l.85 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 fordefining habituation and provides data that shows the process

70- of habituation, there are other factors that can have an effect onhabituation. The authors believe training might affect whether,

60- . when, and how long it takes to achieve habituation. Therefore,

it would be interesting to conduct a similar experiment that,50; *instead of varying the number of interactions, varies the typet 40 0 t *= =and amount of training a participant receives before enrollment

0%=X*s==** 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) changes20. _ - - the progress toward habituation and acclimation.

10 43 . ' = ,, gVII. REFERENCES

0- [1.] A. Jain and N. Duta, "Deformable matching of hand shapes for

G 2 user verification," presented at the 1999 InternationalConference on Image Processing, Kobe, Japan, October 24-

Figure 7. Plot of match score for groups 1 and 2 for week 1 28, 1999.[2.] Zunkel, D., Hand Geometry Based Verification, in Biometrics:

100- Personal Identification in a Networked Society, S. Pankanti,100 Editor. 1999, Kluwer Academic Publishers: Norwell. p. 87-

101.so- [3.] E. Kukula and S. Elliott, "Implementation of hand geometry at

Purdue University's recreational center: An analysis of usere60 * perspectives and system performance," presented at the 39th

Annual International Carnahan Conference on Security= . * =. Technology (ICCST), Las Palmas de Gran Canaria, Spain,

4 4Q = = * .October 12, 2005.4e:0 * * = , i [4.] M. Thieme, D. Setlak, E. Kukula, S. Pankanti, K. Gregory, andN. Sickler, (February 17, 2005), "Ad hoc Report: Effects of

-20 user habituation and acclimation in the context of biometricperformance testing," (No. M1/05-0139), Washington:

~~~~~~~~~ ~~~~~~~~INCITS. Available:0- http:HwwwJncitsorgtc home/r dlhtm/docs/m 10501 39pdf.

Grou'p [5.] M. P. Haines, "Habituation and social norms," The Report onSocial Norms. 2005, 4(7). Available:

Figure 8. Plot of match score for groups 1 and 2 forweek 7 http://www.socialnorm.org/pdf/HainesHabituation.pdf.[6.] Merriam- Webster Online, "Habituation," from http://www.m-

V. CONCLUSION [7.] w.com/dictionary/habituation.V7.] WordNet 2.1, "Habituation," retrieved September 4, 2006, from

This paper outlines a model for determining the levels of http://wordnet.princeton.edu.habituation and provides data on various methods of interacting [8.] The American Heritage® Dictionary of the English Languagewith a hand geometry device, with the objective of (2004, 4th ed), "Habituation," fromdemonstrating the level of training required to use this http://www.thefreedictionary.com/habituation.parntuardic toi best outc e.I

n i appairent, ased on [9.] The American Heritage® Stedman's Medical Dictionary (2004),particular device to itS best outcome. It iS apparent, based on "Aciato, fro htp/eicl- .. ' . ''~~~~~Acclimation"' from http://medical-the data that repeated use of the device yields some increase inthe performance success of participants relative to the device. .10.] .ic .. . . . * [10.] ~~~~~Wikipedia (2006a), "Acclimation," retrieved September 18,The groups whose participants interacted with the device over a 2006, from http://en.wikipedia.org.longer period of time (groups 1 and 4) had lower scores, [11.] Wikipedia (2006b), "Habituation," retrieved September 4, 2006,although fewer interactions (attempts to achieve scores under from http://en.wikipedia.org.

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