NISTIR 7645 Page 1 07/30/2009

NISTIR 7645

Symbols Representing 

Biometrics in Use

Yee-Yin Choong

Mary Theofanos

Brian Stanton

Patrick Hofmann
NISTIR 7645 Page 2 07/30/2009

NISTIR 7645

Symbols Representing 

Biometrics in Use

Yee-Yin Choong

Mary Theofanos

Brian Stanton

Information Access Division

Information Technology Laboratory

National Institute of Standards and Technology

Gaithersburg, MD 20899

Patrick Hofmann

designpH

Toronto London Sydney

July 2009

U.S. Department of Commerce

Gary Locke, Secretary

National Institute of Standards and Technology

Patrick D. Gallagher, Deputy Director
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Table of Contents

1. INTRODUCTION............................................................................................................................................5

2. METHOD .........................................................................................................................................................6

2.1 PHASE 1....................................................................................................................................................6

2.1.1 Materials ........................................................................................................................................6

2.1.2 Participants.....................................................................................................................................7

2.1.3 Procedure .......................................................................................................................................7

2.2 PHASE 2....................................................................................................................................................7

2.2.1 Materials ........................................................................................................................................7

2.2.2 Participants.....................................................................................................................................8

2.2.3 Procedure .......................................................................................................................................8

2.3 PHASE 3....................................................................................................................................................8

2.3.1 Materials ........................................................................................................................................8

2.3.2 Participants.....................................................................................................................................8

2.3.3 Procedure .....................................................................................................................................10

3. RESULTS AND DISCUSSIONS ..................................................................................................................11

3.1 PHASE 1..................................................................................................................................................11

3.2 PHASE 2..................................................................................................................................................12

3.3 PHASE 3..................................................................................................................................................13

3.3.1 Respondents’ Preference Rankings..............................................................................................13

3.3.2 Responses on Symbol Clarity ......................................................................................................15

3.3.3 Responses on Symbol Induced Confusion ...................................................................................15

3.3.4 Responses on Confidence in Symbol Recognition.......................................................................16

3.3.5 Discussions ..................................................................................................................................16

4. CONCLUSION ..............................................................................................................................................17

5. REFERENCES...............................................................................................................................................19

APPENDIX A: PHASE 3 - EMAIL TO INVITE SURVEY PARTICIPANTS............................................20

APPENDIX B: PHASE 3 – EXAMPLE OF BIOMETRICS SYMBOL SURVEY......................................21
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List of Figures

FIGURE 1 ABSTRACT SYMBOL EXAMPLE – RECYCLING SYMBOL.............................................................................6

FIGURE 2 PHASE 3 - RESPONDENTS’ AGE RANGE ...................................................................................................9

FIGURE 3 PHASE 1 - MDS ANALYSIS....................................................................................................................11

FIGURE 4 PHASE 1 RESULT - PREFERRED SYMBOL VARIANT..................................................................................12

FIGURE 5 PHASE 2 RESULT - PREFERRED SYMBOL VARIANTS................................................................................13

FIGURE 6 RESPONDENTS' VOTES FOR THE 3 SYMBOL VARIANTS............................................................................14

FIGURE 7 PHASE 3 RESULT – TWO SYMBOL CANDIDATES FOR “BIOMETRICS IN USE” ...........................................17

FIGURE 8 EXAMPLES OF PUBLIC INFORMATION SYMBOLS FOR “BIOMETRICS IN USE” ..........................................18

FIGURE 9 EXAMPLES OF ALERTING SYMBOLS FOR "BIOMETRICS IN USE" .............................................................18
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1. INTRODUCTION

During the InterNational Committee for Information Technology Standards (INCITS) M1 

task group meetings in 2008, it was recognized that there is a need for a symbol to represent 

that any biometrics (fingerprint, iris, photo, etc.) are in use. The symbol is to be used to 

indicate that biometric collection may be in use, for example, to indicate to the public that 

their photo may be taken or their fingerprints may be scanned. The symbol should be 

independent of any specific biometric collection processes. It will also need to be generic 

such that it is applicable to all of the modalities including iris, face, fingerprint, voice, vein, 

and temperature and any modalities that may be developed in the future.

There is no existing symbol with the intended meaning either in ISO 7001 [1] for public 

information symbols, ISO/IEC 13251 [2] for office equipment, nor in existing ISO standards 

concerning safety symbols for various applications (ISO 3864-1 [3], ISO 7010 [4], ISO 7010 

– Amendment 1 [5], ISO 7010 – Amendment 2 [6], ISO 7010 – Amendment 3 [7], ISO 7010 

– Amendment 4 [8], ISO 6309 [9], ISO 20712-1 [10]). It is apparent that such symbol needs to 

be developed to convey the concept of biometrics in use to people. 

Initially, the intent was to develop a symbol to alert the public that biometrics are in use. The 

National Institute of Standards and Technology (NIST) Biometrics Usability group 

developed a set of symbol variants and performed a study to evaluate those variants. Each 

variant was bordered with the cautionary triangle to convey the alert. The variants were 

evaluated with representative audience in phases. In the first phase, 10 variants were 

evaluated with 49 participants using an interview technique. In the second phase, five

variants (including one variant chosen from phase 1 and four new symbol variants) were 

evaluated with another 50 participants using the same interview technique as in phase 1. 

Two variants were identified as plausible candidates for the intended meaning as the results 

from the first two phases. Those two variants were socialized during the ISO/IEC JTC 1/SC 

37 working group meeting, WG 6 on Cross-Jurisdictional and Societal Aspects, 20-23 

January 2009 in Hawaii. Comments from ISO members regarding the two variants indicated 

that the intended meaning should be informative, rather than alerting, to the general public 

about biometrics in use. ISO members were concerned that the triangular border which 

implies warning may cause the public perceive biometrics collection as alarming and 

harmful. Based on the comments, another set of three variants without the triangular border 

was developed and a phase 3 evaluation has been conducted with an on-line survey. The 

objective of the survey was to reach out an audience with broader backgrounds such as age, 

occupations, and ethnicity.
NISTIR 7645 Page 6 07/30/2009

2. METHOD

This study was conducted in three phases. The details of each phase are described in the 

following sections.

2.1 PHASE 1

2.1.1 Materials

Initially, a set of twenty-four, black-and-white symbol variations were developed, each 

bordered with a cautionary triangle. The purpose of the symbols is to provide general 

indication to the public that any biometrics may be in use. Due to its objective of being 

generic, the design concept was to create symbols that may be abstract to portrait the generic 

nature, yet can be perceived uniquely and will be learned and remembered. Such design 

concept can be illustrated by the well known standard recycling symbol (ISO 7000-1135 in 

ISO/IEC 13251 [2]), in Figure 1, which was designed to be memorable but abstract. The 

recycling symbol has been learned and recognized by the general public.

Figure 1 Abstract symbol example – recycling symbol

Three experts at NIST reviewed and reduced the set to 10 symbol variants (Table 1) based on 

information available to NIST experts regarding the intended purpose of the symbol at the 

time of the review. 

Table 1 Symbol Variants for Phase 1

variant 1-1 variant 1-2 variant 1-3 variant 1-4 variant 1-5

variant 1-6 variant 1-7 variant 1-8 variant 1-9 variant 1-10
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2.1.2 Participants

The recruitment of participants was cautioned to exclude anyone whose job or background is 

related to biometrics to eliminate possible biases. Forty-nine NIST employees volunteered to 

participate in phase 1 evaluation. 

2.1.3 Procedure

An one-on-one interview technique was used in phase 1. All interviews were conducted in 

the participants’ office. The interviewer provided each participant with the background of the 

study, explaining that we were designing symbols to indicate that biometrics are in use in the 

vicinity, similar to the warning sign of surveillance video in use in the building where his/her 

office is. The interviewer further explained that symbols of this kind are generally learned, 

for example, the recycling symbol (Figure 1) that cannot be recognized without learning it 

first. The symbol we are trying to develop will need to be learned but should be memorable 

and linked to biometrics. It will also need to be generic such that it is applicable to all of the 

biometric modalities.

The interviewer informed each participant that there would be 10 symbol variants (Table 1)

and asked the participant to order them from the one most appropriate for a general symbol 

indicating biometrics in use to the one least appropriate. Each participant received a stack of 

10 sheets of paper, each paper with only one symbol variant printed on it. The presentation 

sequence of the 10 variants was randomized for each participant to eliminate any sequence 

effects. There was no time limit on ordering the symbol variants. The participants indicated

to the interviewer when they finished the task. Any comments made by the participants were 

noted by the interviewer.

2.2 PHASE 2

2.2.1 Materials

In phase 2, four additional symbols were developed and evaluated with the most preferred 

symbol variant (variant 1-6 in Table 1) from phase 1. As the variants in phase 1 were mainly 

abstract, it was the intention in phase 2 to test symbols with a range of abstract and concrete 

concepts. Total of five variants were evaluated, as shown in Table 2.

Table 2 Symbol Variants for Phase 2

variant 2-1 variant 2-2 variant 2-3 variant 2-4 variant 2-5
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2.2.2 Participants

Same as in phase 1, the recruitment of participants was cautioned to exclude anyone whose 

job or background is related to biometrics so that possible biases were eliminated. The 

recruitment also excluded anyone who participated in phase 1. Fifty NIST employees 

volunteered to participate in phase 2 evaluation. 

2.2.3 Procedure

The procedure was the same as in phase 1. All interviews were conducted in the participants’ 

office. The interviewer provided each participant with the same information regarding the 

study and the context of use as given in phase 1.

The interviewer informed each participant that there would be five symbol variants (Table 2) 

and asked the participant to order them from the one most appropriate for a general symbol 

indicating biometrics in use to the one least appropriate. Each participant received a stack of 

five sheets of paper, each paper with only one symbol variant printed on it. The presentation 

sequence of the five variants was randomized for each participant to eliminate any sequence 

effects. There was no time limit on ordering the symbol variants. The participants indicated 

to the interviewer when they finished the task. Any comments made by the participants were 

noted by the interviewer.

2.3 PHASE 3

2.3.1 Materials

Three symbol variants were developed without the warning triangular borders: two variants

were the results from phase 2 and one was new. Those three variants (Table 3) were 

evaluated in phase 3.

Table 3 Symbol Variants for Phase 3

variant 3-1 variant 3-2 variant 3-3

2.3.2 Participants

In order to reach out to a broader audience, an invitation email of a survey was sent to a 

nation-wide user pool of about 12,000 people with various backgrounds such as gender, age, 

education, occupation, and ethnicity. The email was carefully written in plain English to 
NISTIR 7645 Page 9 07/30/2009

ensure that all readers with different backgrounds can understand it. The email was finalized 

(Appendix A) after an 8-year-old, 2nd grader proofread it with complete comprehension. If 

any of the email recipients decided to participate, he/she would access the survey via an URL 

provided within the email.

2.3.2.1 Demographics

Within a two-week span, total of 725 respondents took the survey. There were 520 females, 

202 males, and three respondents who chose not to identify their genders. The age of the 

respondents ranged from 18 to above 75 (Figure 2), with majority (76.7%) between 25 and 

54.

59

150

186

220

82

21

2

5

0 50 100 150 200 250

18-24

25-34

35-44

45-54

55-64

65-74

75 and over

(not specified)

Count

Age

Figure 2 Phase 3 - Respondents’ Age Range

The respondents’ ethnic backgrounds were diverse with majority white Americans. The 

respondents’ jobs covered a wide range of occupations. The respondents’ ethnic backgrounds 

and occupations are summarized in Table 4. 

Table 4 Phase 3 - Respondents' Ethnicity and Occupations

Ethnic Backgrounds Count (%) Occupations Count (%)

White American 542 (74.8%) Administrative support worker 94 (13.0%)

African American 85 (11.7%) Craft worker 16 (2.2%)

Latino American 34 (4.7%) Homemaker 137 (18.9%)

American Indian or Alaskan Native 6 (0.8%) Laborer 41 (5.7%)

East Asian American 3 (0.4%) Professional 198 (27.3%)

South Asian American 6 (0.8%) Retired 61 (8.4%)

Native Hawaiian or other Pacific Islander 1 (0.1%) Sales worker 21 (2.9%)

Canadian 2 (0.3%) Service worker 40 (5.5%)

East Asian 6 (0.8%) Student 42 (5.8%)

European 9 (1.2%) Technician 29 (4.0%)
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Latino 4 (0.6%) Other 46 (6.3%)

Mediterranean 3 (0.4%)

South Asian 10 (1.4%)

Other 14 (1.9%)

2.3.3 Procedure

An on-line survey (Appendix B)1

To eliminate any possible biases that may result from the presentation sequence of the three

symbol variants evaluated, six variations of the survey were created to account for all 

possible symbol presentation sequences. All follow-up questions regarding individual 

symbol variants were arranged in the same sequence as how the variants were presented in 

the preference question (Question 5 on the survey, Appendix B). For example, in Appendix 

B, it shows survey variation 5 with the symbol presentation sequence: variant 3-1, variant 3-

2, and variant 3-3. 

was developed to collect respondents’ preferences on the 

symbol variants for “biometrics in use”. The survey also collected respondents’ opinions on 

each symbol variant, concerning its clarity, whether it causes confusion, and the extent that 

the respondents feel confident to recognize the symbol variant with its intended meaning in 

the future.

The six survey variations were roughly even-distributed to respondents (Table 5). When the 

first respondent accessed the on-line survey, the first survey variation was displayed. The 

second survey variation was displayed to the second respondent, then the third respondent 

will see survey variation 3, and so on. The six survey variations followed in sequence and in 

cycles. 

Table 5 Survey Variations Presented to Respondents

Survey 

Variations

Sequence # of Respondents

1 variant 3-3, variant 3-1, variant 3-2 127

2 variant 3-3, variant 3-2, variant 3-1 132

3 variant 3-2, variant 3-1, variant 3-3 114

4 variant 3-1, variant 3-3, variant 3-2 119

5 variant 3-1, variant 3-2, variant 3-3 120

6 variant 3-2, variant 3-3, variant 3-1 113

Total 725

 1 The OMB number for this survey is 0693-0043, expiring on 7/31/2009.
NISTIR 7645 Page 11 07/30/2009

3. RESULTS AND DISCUSSIONS

3.1 PHASE 1 

After each participant ordered the 10 symbol variants based on his/her preference, the 

rankings (1 to 10) were recorded, with “1” denoting the most preferred variant and “10” the 

least preferred variant. The preference rankings are summarized in Table 6 for each symbol 

variant: each cell lists the number of participants who ordered the variant with the specific 

rank. For example, the top left-most cell indicates that there were 10 participants who 

ordered variant 1-1 as their most preferred symbol.

Table 6 Counts of participants' rankings for phase 1 symbol variants

Ranks V 1-1 V 1-2 V 1-3 V 1-4 V 1-5 V 1-6 V 1-7 V 1-8 V 1-9 V 1-10

1st 10 2 2 2 5 9 6 1 6 6

2nd 5 4 5 2 4 7 6 4 5 7

3rd 1 6 6 2 2 3 9 7 7 6

4th 3 5 6 8 2 7 4 1 9 3

5th 3 3 5 4 7 5 9 5 0 8

6th 2 10 5 2 4 6 4 10 2 4

7th 3 8 3 4 3 6 7 4 8 3

8th 6 2 10 1 2 2 1 12 7 5

9th 2 6 6 14 8 3 2 2 4 3

10th 14 3 1 10 12 1 1 3 1 4

As the rankings over the 10 symbol variants were ordinal and related (within participants), a 

non-parametric test, the Friedman’s analysis of variance by ranks, was used. Differences in

preferences across symbol variants were significant, χ

2

(9) = 32.865, p<=0.0001.

Derived Stimulus Configuration

Euclidean distance model

Dimension 1

-2.0 -1.5 -1.0 -.5 0.0 .5 1.0 1.5 2.0

Dimension 2

1.5

1.0

.5

0.0

-.5

-1.0

-1.5

-2.0

f10

f9

f8

f7

f6

f5

f4

f3f2 f1

Figure 3 Phase 1 - MDS Analysis
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The Multidimensional Scaling (MDS) method was used to detect any possible underlying 

dimensions that may explain the similarities or dissimilarities between the preference data 

collected from the forty-nine participants for those 10 symbol variants in phase 1. The results 

of the MDS analysis is shown in Figure 3, where f1to f10 represent symbol variant1-1 to 

variant 1-10, respectively. 

The vertical dimension (Dimension 2) appears to represent “preference”, with higher values 

for higher preferences. The horizontal dimension (Dimension 1) seems to be a measure of 

symbol complexity – high numbers show the simple cases and negative ones are more 

complex. Based on the MDS analysis, one symbol (f6, i.e. variant 1-6), shown in Figure 4,

was chosen to be moved forward for phase 2 evaluation as it was scored the highest in 

preference and on the positive side of symbol complexity. 

Figure 4 Phase 1 result - preferred symbol variant

3.2 PHASE 2 

After each participant ordered the five symbol variants based on his/her preference, the 

rankings (1 to 5) were recorded, with “1” denoting the most preferred variant and “5” the 

least preferred variant. The preference rankings are summarized in Table 7 for each symbol 

variant: each cell lists the number of participants who ordered the variant with the specific

rank.

Table 7 Counts of participants' rankings for phase 2 symbol variants

Ranks V 2-1 V 2-2 V 2-3 V 2-4 V 2-5

1st 20 5 7 16 10

2nd 11 9 14 12 4

3rd 5 11 13 9 10

4th 11 14 8 9 5

5th 3 11 8 4 21

Friedman’s analysis of variance by ranks was used on these five symbol variants and their 

rankings received from the participants. Differences in preferences across symbol variants 

were significant, χ

2

(4) = 18.892, p<=0.0008.

To further examine the data, the Wilcoxon Matched-Pairs Signed-Ranks Test was used to 

compare participants’ preferences on the symbol variants (Table 8). With significant level at 

α=0.01, variant 2-1 was ranked significantly higher when compared to variants 2-2 and 2-5; 
NISTIR 7645 Page 13 07/30/2009

variant 2-4 was ranked significantly higher when compared to variants 2-2 and 2-5. There 

was no significance between variant 2-1 and variant 2.4. There were no significant 

differences of variant 2-3 when compared to other variants.

From the comparisons, variants 2-1 and 2-4 appear to be the most preferred symbols to 

represent the concept of “biometrics in use”. Thus, those two symbol variants (Figure 5) 

were chosen as candidates and were socialized at the ISO/IEC JTC 1/SC 37 WG 6 working 

group meeting in Hawaii to solicit feedback from ISO members. 

Table 8 Comparisons of preference rankings among Symbol Variants

Variant 2-1 Variant 2-2 Variant 2-3 Variant 2-4

Variant 2-2 W= 261.50, p<=0.001* 

Variant 2-3 W= 433.5, p<=0.05 W= 437, p<=0.10 

Variant 2-4 W= 597.5, p>0.2 W= 356, p<=0.01* W= 462.50, p<=0.20 

Variant 2-5 W= 343, p<=0.005* W= 578.5, p>0.2 W= 426, p<=0.10 W= 261.50, p<=0.001*

 Figure 5 Phase 2 result - preferred symbol variants

The WG6 members were concerned with the symbols being warning signs as these symbols 

may be perceived by the general public that the use of biometrics could be dangerous or 

harmful. They recommended developing an informative symbol to communicate to general 

public the concept that biometrics may be in use in the vicinity surroundings. As discussed 

earlier, to address the concerns raised by WG6 members, another set of three variants 

without the triangular border was developed and was evaluated in phase 3.

3.3 PHASE 3 

3.3.1 Respondents’ Preference Rankings

Out of the 725 people who took the on-line survey, 16 respondents’ data were excluded from 

data analysis as they did not cast any votes toward the three variants in Question #5 on the 

survey (see Appendix B). Partial votes, for example, votes were casted for 1 or 2 variants, 

were included in data analysis. Total of 709 respondents’ data were included in the analyses. 

The counts of respondents voting for the variants as 1st, 2nd, or 3rd are shown in Figure 6.

As the votes over the three symbol variants were ordinal and related (within participants), the 

Friedman’s analysis of variance by ranks, was used. Differences of preferences across 

symbol variants were significant, χ

2

(2) = 280.930, p=0.0000.
NISTIR 7645 Page 14 07/30/2009

To further examine the data, the Wilcoxon Matched-Pairs Signed-Ranks Test was used to 

compare participants’ preferences on the symbol variants. At α=0.01, variant 3-1 was ranked 

significantly higher when compared to variants 3-3 (p=0.0000); variant 3-2 was ranked 

significantly higher when compared to variants 3-3 (p=0.0000). There was no significance 

between variant 3-1 and variant 3.2 (p=0.027) at α=0.01, but the difference was significant at 

α=0.05, with variant 3-1 ranked higher than variant 3-2. 

367

244

93

194

355

151

138 101

453

0

100

200

300

400

500

600

700

800

Variant 3-1 Variant 3-2 Variant 3-3

Counts

1st 2nd 3rd

Figure 6 Respondents' votes for the 3 symbol variants

To determine whether the preference rankings were different among different age groups, the 

Friedman’s analysis of variance by ranks was used. Differences in preferences across symbol 

variants were significant among different age groups, χ

2

(2) = 10.75, p=0.0046, at α=0.01.

The score rankings within age groups from Friedman test are listed in Table 9. The age group 

of “75 and over” was the only group with different ranking patterns that the participants in 

this group preferred variant 3-3, followed by variant 3-1, then variant 3-2; whereas all other 

age groups gave variant 3-1 top rank, followed by variant 3-2, then variant 3-3. It should be 

noted that the “75 and over” age group consisted only two participants which represented a 

very small percentage (0.28%) of the survey participants.

Table 9 Score rankings on symbol variants within age groups

Score Rankings

Age Group Variant 3-1 Variant 3-2 Variant 3-3

18-24 (n=57) 1 2 3

25-34 (n=148) 1 2 3

35-44 (n=182) 1 2 3

45-54 (n=213) 1 2 3

55-64 (n=81) 1 2 3

65-74 (n=21) 1 2 3

75 and over (n=2) 2 3 1

Not specified (n=5) 1 2 3
NISTIR 7645 Page 15 07/30/2009

To examine whether there were gender differences in ranking the symbol variants, 

Friedman’s analysis of variance by ranks was used. Three respondents who did not specify 

their genders were excluded from this analysis. There were 198 males and 508 females. 

Differences in preferences across symbol variants between male and female respondents 

were not significant, χ

2

(2) = 4.000, p=0.1353, at α=0.01.

3.3.2 Responses on Symbol Clarity

For each symbol variant, respondents were asked a question: “The symbol clearly describes 

the concept of biometrics in use.” The question used Likert-scale ratings, with “1” as 

“Unclear” and “5” as “Completely clear.”

A non-parametric analysis, Kruskal-Wallis one-way ANOVA, was used. Differences in the 

ratings on symbol clarity across symbol variants were significant, H=455.8078 (critical value 

for χ

2 with p<=0.01 and 2 df is 7.82).

To further examine the data, the Mann-Whitney U test was used to compare participants’ 

opinion ratings on symbol clarity. The medians and the Mann-Whitney U test results are 

listed in Table 10. With significant level at α=0.01, variant 3-1 was rated significantly higher 

on symbol clarity than variant 3-2 and variant 3-3, and variant 3-2 was rated significant 

higher than variant 3-3. 

Table 10 Medians and comparisons of ratings on symbol clarity 

Variant 3-1 Variant 3-2 Variant 3-3

Variant 3-2 U=320521, p=0.0000

Variant 3-3 U=230720, p=0.0000 U=386779.5, p=0.0000

Median (n=725) 4 3 1

3.3.3 Responses on Symbol Induced Confusion

For each symbol variant, respondents were asked a question: “The symbol is confusing.” The 

question used Likert-scale ratings, with “1” as “Not confusing” and “5” as “Completely 

confusing.”

A non-parametric analysis, Kruskal-Wallis one-way ANOVA, was used. Differences in the 

ratings on symbol clarity across symbol variants were significant, H=393.5126 (critical value 

for χ

2 with p<=0.01 and 2 df is 7.82).

Table 11 Medians and comparisons of ratings on symbol induced confusion

Variant 3-1 Variant 3-2 Variant 3-3

Variant 3-2 U=313990, p=0.0000

Variant 3-3 U=412485, p=0.0000 U=374825.5, p=0.0000

Median (n=725) 1 2 3

To further examine the data, the Mann-Whitney U test was used to compare participants’ 

opinion ratings on the degree that symbols appear to be confusing to the participants. The 
NISTIR 7645 Page 16 07/30/2009

medians and the Mann-Whitney U test results are listed in Table 11. With significant level at 

α=0.01, variant 3-1 was rated significantly as being less confusing than variant 3-2 and 

variant 3-3, and variant 3-2 was rated significant less confusing variant 3-3. 

3.3.4 Responses on Confidence in Symbol Recognition

For each symbol variant, respondents were asked a question: “How confident are you that 

you would recognize the symbol as biometrics in use if you saw it in the future?” The 

question used Likert-scale ratings, with “1” as “Not confident” and “5” as “Completely 

confident.”

A non-parametric analysis, Kruskal-Wallis one-way ANOVA, was used. Differences in the 

ratings on symbol clarity across symbol variants were significant, H=377.8455 (critical value 

for χ

2 with p<=0.01 and 2 df is 7.82).

To further examine the data, the Mann-Whitney U test was used to compare participants’ 

opinion ratings on confidence in recognizing symbol in the future. The medians and the 

Mann-Whitney U test results are listed in Table 12. With significant level at α=0.01, variant 

3-1 was rated significantly higher on confidence in recognizing the symbol in the future than 

variant 3-2 and variant 3-3, and variant 3-2 was rated significant higher than variant 3-3. 

Table 12 Medians and comparisons of ratings on confidence in symbol recognition

Variant 3-1 Variant 3-2 Variant 3-3

Variant 3-2 U=320109.5, p=0.0000

Variant 3-3 U=409744, p=0.0000 U=368788.5, p=0.0000

Median (n=725) 4 3 2

3.3.5 Discussions

From the results, variant 3-1 (Figure 7(a)) is the best candidate for representing the concept 

of “biometrics in use” as it received highest preference ranking, was perceived as clearer and 

less confusing and respondents felt more confident to recognize the symbol in the future. 

However, some respondents shared their concerns that, although the symbol is well 

recognized and understood, it is too specific representing only single modality which may 

limit its capability to be generalized in the situation where multiple modalities are in use. For 

example, one respondent stated “I do think it clearly displays biometrics as a symbol but it 

does not define the whole spectrum of what can be used.” Another respondent commented 

“This symbol gives the impression of fingerprints only whereas the other symbols suggests 

more.” One respondent also stated “I associate this symbol with a fingerprint, and nothing 

else. This symbol I have already seen for things requiring a simple fingerprint, and I would 

not associate it with the wider scope of biometrics.”
NISTIR 7645 Page 17 07/30/2009

(a) (b)

Figure 7 Phase 3 result – two symbol candidates for “Biometrics in Use”

Variant 3-2 (Figure 7(b)) seems to be another plausible candidate as its preference ranking 

was not significantly different from variant 3-1. And, it was rated second consistently 

regarding its clarity, induced confusion, and respondents’ confidence in recognizing it in the 

future. Respondents who ranked it first pointed out that it covers a broader spectrum of 

biometric modalities. One respondent commented “[variant 3-2] symbolizes everything for 

biometrics.” Another respondent stated “Biometrics is a finger print, eye scan, or a face 

photo and this symbol is the best!” Some respondents who ranked it second were mainly 

concerned with the small size of the fingerprint image in the center that may cause 

recognition problems when the symbol is reduced to smaller sizes, for example, as an icon on 

a computer screen. One respondent commented “As long as it was good size it would work. 

The smaller the worse it becomes.” Another respondent stated “this symbol captures 

biometrics but if the symbol is minimized, I [can] barely see the fingerprint.” Another noted 

“My only reason for not voting this icon in the #1 position is due to the fingerprint being too

small for some to easily view. If the fingerprint were larger/easier to identify, I'd use this as 

the first choice.”

4. CONCLUSION

From the results, two variants are plausible candidates to be proposed to the ISO/IEC JTC 

1/SC 37 WG 6 for consideration to represent the concept of “biometrics in use.” It is 

recommended to use variant 3-1, i.e. fingerprint image (Figure 7(a)), when only the 

fingerprint collection is in use. When multiple modalities are in use, variant 3-2 (Figure 7(b))

is to be used. 

When the symbols are to be used as public information symbols, they can be reproduced in 

any color and be enclosed with borders (ISO 7001 [1]). Examples of how the two symbols 

can be presented as public information symbols with optional supplementary text are 

demonstrated in Figure 8 (a) and (b).
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(a) (b)

Figure 8 Examples of public information symbols for “Biometrics in Use”

If the symbols were to be used as alerting symbols for certain situations, such as in 

workplaces and public areas, design principles outlined in ISO 3864-1 [3] should be 

followed. A warning sign shall use yellow safety color, black contrast color, and be 

displayed in an equilateral triangle. Examples of the symbols for “biometrics in use” used as 

alerting signs optional supplementary text are demonstrated in Figure 9 (a) and (b).

(a)

(b)

Figure 9 Examples of alerting symbols for "Biometrics in Use"

Some future research is needed before finalizing the symbol variants for representing the 

concept of “Biometrics in Use.” Firstly, based on comments made by the survey respondents, 

the fingerprint image in both variants may need to be simplified to address respondents’ 

concerns on legibility and also to help in image scaling, especially when reducing the size of 

the symbols is necessary. Secondly, these symbols need to be evaluated in an operational 

environment where the symbols will be used to ensure that the general public is informed of 

“biometrics in use” by the symbol. Thirdly, the symbols should be evaluated in other 

countries to understand if there will be any cultural implications.
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5. REFERENCES

[1] International Organization for Standards. ISO 7001 Graphical symbols – Public information 

Geneva, Switzerland: Author, (2007). 

[2] International Organization for Standards. ISO/IEC 13251 Collection of graphical symbols for 

office equipment Geneva, Switzerland: Author, (2004). 

[3] International Organization for Standards. ISO 3864-1 Graphical symbols – Safety colours 

and safety signs – Part 1: Design principles for safety signs in workplaces and public areas 

Geneva, Switzerland: Author, (2002). 

[4] International Organization for Standards. ISO 7010 Graphical symbols – Safety colours and 

safety signs – Safety signs used in workplace and public areas Geneva, Switzerland: Author, 

(2003). 

[5] International Organization for Standards. ISO 7010 Graphical symbols –Safety colours and 

safety signs – Safety signs used in workplace and public areas, Amendment 1 Geneva, 

Switzerland: Author, (2006). 

[6] International Organization for Standards. ISO 7010 Graphical symbols –Safety colours and 

safety signs – Safety signs used in workplace and public areas, Amendment 2 Geneva, 

Switzerland: Author, (2007). 

[7] International Organization for Standards. ISO 7010 Graphical symbols –Safety colours and 

safety signs – Safety signs used in workplace and public areas, Amendment 3 Geneva, 

Switzerland: Author, (2007). 

[8] International Organization for Standards. ISO 7010 Graphical symbols –Safety colours and 

safety signs – Safety signs used in workplace and public areas, Amendment 4 Geneva, 

Switzerland: Author, (2009). 

[9] International Organization for Standards. ISO 6309 Fire protection – safety signs Geneva, 

Switzerland: Author, (1987). 

[10] International Organization for Standards. ISO 20712-1 Water safety signs and beach 

safety flags – Part 1: Specifications for water safety signs used in workplaces and public 

areas Geneva, Switzerland: Author, (2008). 
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APPENDIX A: PHASE 3 - EMAIL TO INVITE SURVEY PARTICIPANTS

Dear Survey Participant,

The international community is voting on symbols for biometric systems such as fingerprint, 

eye (iris) scans, and face photo. The United States National Institute of Standards and 

Technology (NIST) is working with the international community to identify symbols that can 

be used anywhere in the world with biometric systems. We are currently voting on a symbol 

to inform people that biometrics are being collected. 

In general symbols are learned. For example you learned that a stop sign is red and has 8 

sides and that a caution sign is a yellow triangle. You would not recognize these without 

someone teaching you.

The symbol we are voting on will need to be learned. The symbol should also be easy to 

remember and remind you of biometrics. It will be used to identify all types of biometrics 

including eye, face photo, and fingerprint. 

We need your vote. Please help us find the biometric symbol by completing a short 

questionnaire. It will only take 5 minutes. 

Simply click on the link below or copy the link into your Internet browser. The link will 

only be available for the next 10 days.

http://control.nist.gov/biometrics/cgi/biometrics_survey.cgi

Thank you 

Sincerely,

The NIST Team,

biosymbol@nist.gov
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APPENDIX B: PHASE 3 – EXAMPLE OF BIOMETRICS SYMBOL SURVEY

This example shows a variant (out of six variants) of the survey as it was presented on the 

internet. 
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