The Perceived Urgency of Tactile Patterns

by Timothy L. White

ARL-TR-5557 June 2011

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Army Research Laboratory

Aberdeen Proving Ground, MD 21005-5425

ARL-TR-5557 June 2011

The Perceived Urgency of Tactile Patterns

Timothy L. White

Human Research and Engineering Directorate, ARL

Approved for public release; distribution is unlimited.
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The Perceived Urgency of Tactile Patterns

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Timothy L. White

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14. ABSTRACT

The purpose of this research was to examine the effects of stimulus intensity and inter-stimulus interval (ISI) on the perceived urgency and on 

the detection and identification of tactile patterns. A tactile system that includes an adjustable belt developed by Engineering Acoustics Inc. 

(EAI) was used to provide tactile stimuli. This adjustable belt, which consists of eight EAI C2 tactors positioned at 45-degree intervals, was 

worn around each participant’s waist. Participants received tactile patterns at an intensity of either 12 dB or 23.5 dB with an ISI of either 

0 ms (no interval) or 500 ms. Participants were asked to identify each tactile pattern that they received and rate how urgent they perceived the 

pattern to be on a scale of 1 to 10. Results show that participants were able to detect and identify tactile patterns with nearly 100% accuracy. 

Participants rated patterns that were provided at the 23.5 dB intensity with no ISI as the most urgent. Patterns provided at the 12 dB intensity 

with a 500 ms ISI were rated the least urgent.

15. SUBJECT TERMS

tactile, urgency, patterns

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Timothy L. White

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Contents

List of Figures v

List of Tables v

Acknowledgment vi

1. Introduction 1

2. Hypotheses 2

3. Objective 2

4. Method 2

4.1 Participants......................................................................................................................2

4.2 Apparatus.........................................................................................................................3

4.2.1 Tactile System .....................................................................................................3

4.2.2 Tactile Patterns....................................................................................................4

4.2.3 Desktop Computer/Headphones..........................................................................5

4.2.4 Questionnaire.......................................................................................................6

4.3 Experimental Design .......................................................................................................6

4.4 Training ...........................................................................................................................7

4.5. Testing.............................................................................................................................8

5. Results 9

5.1 Perceived Urgency ..........................................................................................................9

5.2 Percent Detected............................................................................................................10

5.3 Overall Percent Correct.................................................................................................12

5.4 Identification Difficulty.................................................................................................14

6. Discussion 14

7. Conclusions and Future Work 16

8. References 17
iv

Appendix A. Volunteer Agreement Affidavit 19

Appendix B. Post-Block Questionnaire 23

Appendix C. Descriptive Statistics (Means and Standard Error of the Means[SEM]) 25

Distribution List 28
v

List of Figures

Figure 1. Tactile communications system. .....................................................................................3

Figure 2. Tactile patterns. ...............................................................................................................4

Figure 3. ISI and pattern durations. ................................................................................................5

Figure 4. SYNWORK arithmetic task. ...........................................................................................6

Figure 5. Participant donning tactile belt........................................................................................8

Figure 6. Inter-Stimulus Interval × Intensity interaction (rating of perceived urgency). .............10

Figure 7. Inter-Stimulus Interval × Intensity interaction (percent detected). ...............................11

Figure 8. Inter-Stimulus Interval × Pattern interaction (percent detected). ..................................11

Figure 9. Inter-Stimulus Interval × Intensity interaction (overall percent correct).......................12

Figure 10. Intensity (12 dB) × Pattern × Arithmetic interaction (overall percent correct)...........13

Figure 11. Intensity (23.5 dB) × Pattern × Arithmetic interaction (overall percent correct)........13

Figure 12. Mean rating of pattern identification difficulty by arithmetic.....................................14

List of Tables

Table 1. Urgency combinations. .....................................................................................................5

Table 2. Independent variables and levels. .....................................................................................6
vi

Acknowledgment 

The author would like to express appreciation to the following individuals who assisted in the 

conduct of this research:

• Dan Cassenti, Ph.D. for the development of the SYNWORK arithmetic application,

• Major Koch and Staff Sergeant Austin for their assistance in obtaining volunteers from the 

U.S. Marine Corps Detachment for this study,

• Asisat Animashaun, Frank Morelli, and Thomas Smith for their assistance with data 

collection.

Last, but never least, the author would like to thank the Marines who participated in this research 

for their enthusiasm and dedication to this project.
1

1. Introduction

In recent years, there has been an increased interest in tactile displays because of the need to 

provide complex information to users who are subject to visual and auditory overload and 

because of the development of more sophisticated tactile display technology (Jones and Sarter, 

2008). Much of the information that Soldiers are currently being provided with is presented 

visually and auditorily. As future technologies advance, Soldiers will be provided with even 

more information regarding combat situations. The multiple-resource theory suggests that 

offloading information from overtaxed sensory modalities to other modalities can reduce 

workload (Wickens, 2002). Tactile displays may be a viable solution to help mitigate the 

overload and performance degradation that can result from this abundance of information being 

provided to Soldiers. If designed and implemented properly, tactile displays may improve 

Soldiers’ situational awareness and survivability on the battlefield. 

A number of research efforts have already shown the potential of tactile display systems in 

military environments. Research efforts to employ tactile displays for orientation, navigation, 

and communication are ever increasing (van Erp and Self, 2008). Some researchers are 

interested in the use of tactile patterns to communicate more complex messages. For example, 

Brewster and Brown (2004) addressed some basic approaches to developing “Tactons” or tactile 

icons to communicate messages. In one study that compared conventional Army hand and arm 

signals to tactile patterns, Soldiers were able to receive, interpret, and accurately respond to the 

tactile patterns faster than with the hand and arm signals while negotiating an obstacle course 

(Pettitt et al., 2006). In another investigation, participants were able to identify and navigate 

using tactile patterns with almost perfect accuracy (Jones et al., 2006). In an extension of this 

work Krausman and White (2006) found that pattern detection and identification rates were 

degraded while participants negotiated obstacles. A noteworthy difference in the Pettitt et al.

(2006) investigation and the other two mentioned investigations is the type of tactile system 

used. The Pettitt et al. (2006) investigation employed an acoustic transducer in which the 

intensity was higher than the pancake motors used in the other two investigations.

Parameters such as frequency, amplitude, and duration of tactile signals have been used to 

encode tactile patterns (Brewster and Brown, 2004). In military environments, some signals or 

messages may need to be encoded with some level of urgency. Research has shown significance 

in the perceived urgency of auditory signals by varying temporal parameters. In one study, interpulse intervals had a consistent effect on the perceived urgency of auditory signals, in that 

signals with shorter inter-pulse intervals and higher sound pressure levels were rated as more 

urgent (Haas and Edworthy, 1996). Similarly, varying inter-stimulus intervals (ISIs) in tactile 

patterns may also be a possible method of displaying urgency. The findings of another study that 

employed “Tactons” that were created from a combination of spatial location, rhythm, and 
2

roughness suggest that varying tactor intensity may also be a feasible alternative of displaying 

urgency (Brown et al., 2006).

2. Hypotheses

Because inter-sitmulus intervals have been successfully used to distinguish urgency in auditory 

signals, it was hypothesized that tactile patterns that have no ISI and a greater (23.5 dB) intensity 

would be rated the most urgent and patterns with a longer (500 ms) ISI and a lower (12 dB) 

intensity would be rated the least urgent. In one investigation, there were no significant 

differences found in detection and localization of tactile signals between two signals, one 20 dB 

and the other 23.5 dB above mean threshold tactor intensity (Krausman and White, 2008). Also, 

weak signals may go unnoticed (Gilson et al., 2007). Furthermore, it is not known how the 

varying intensity and ISIs will interact with each other. It was hypothesized that detection and 

identification rates would be degraded when the arithmetic distractor task was performed.

3. Objective

The objective of this laboratory study was to quantify the effects of ISI and stimulus intensity on 

perceived urgency and on the detection and identification of tactile patterns.

4. Method

4.1 Participants

Sixteen male Marines from the U.S. Marine Corps Detachment at Aberdeen Proving Ground, 

MD, volunteered to participate in this research. All participants were 19 years of age (19.5 years 

±0.5). All participants had vision sufficient (corrected or uncorrected) for driving. Participants 

had normal hearing, as determined by an audiogram.

The voluntary, fully informed consent of the persons used in this research was obtained as 

required by 32 Code of Federal Regulations (CFR) 219 and Army Regulation (AR) 70-25 

(1990). The investigators adhered to the policies for the protection of human subjects as 

prescribed in AR 70-25.
3

4.2 Apparatus

4.2.1 Tactile System

An Engineering Acoustics Inc. (EAI) C2 tactile system was used, which consists of an adjustable 

tactile belt display (figure 1) worn around the waist and a receiver unit. The adjustable belt 

display consists of eight EAI C2 tactors (acoustic transducers) that are approximately 1.2 inches 

in diameter. A belt display was used because, in a more realistic dismounted combat situation, it 

will allow stimuli to be easily perceptible and will be less likely to shift as opposed to other body 

locations during physically demanding tasks (Merlo et al., 2006). Previous research findings 

have proven the feasibility of an eight-tactor belt display (Cholewiak et al., 2004). Each of the 

eight tactors is positioned at 45-degree intervals in the adjustable belt. The tactors can be 

activated individually, sequentially, or in groups to provide a specific sensation or to create 

unique patterns of vibration. The tactor control unit is capable of receiving wired or wireless 

signals and converts them into recognizable patterns of vibration. The system, which provides 

the capability to vary signal frequency, gain, and duration, is powered by a 9.6 V nickel-metal 

hydride (Ni-MH) battery.

Figure 1. Tactile communications system.
4

4.2.2 Tactile Patterns

Four tactile patterns were provided via a tactile belt during this experiment. These patterns were 

developed based on the work of Jones et al. (2006) in which similar tactile patterns were used in 

a 4 × 4 back display. In figure 2, for each pattern, the numbers indicate the sequence in which 

tactors vibrated. The duration of the vibrations were 500 ms. Participants received these 

patterns with varying intensity and ISIs. All patterns were provided at a frequency of 250 Hz. 

The intensity of each pattern was presented at either an EAI gain setting of 2 (12 dB) or 4 

(23.5 dB), and the ISI of each pattern was either 500 ms or 0 ms. Therefore, tactile patterns with 

an ISI of 500 ms had a total duration of 3.5 seconds (s), and tactile patterns with an interstimulus interval ISI of 0 ms had a total duration of 2.0 s (figure 3). The gain settings refer to the 

mean ratio of tactor output to the voltage input.

Figure 2. Tactile patterns.
5

Figure 3. ISI and pattern durations.

The two intensity levels and the two ISI levels were combined to form four urgency 

combinations as shown in table 1. Each of the 4 patterns with each urgency combination was 

provided 4 times during each block for a total of 64 patterns per block. There was a three to six 

second interval between each pattern. The patterns and urgency combinations were 

counterbalanced using a Williams square.

Table 1. Urgency combinations.

Inter-Stimulus Interval Intensity

0 ms 12 dB

0 ms 23.5 dB

500 ms 12 dB

500 ms 23.5 dB

4.2.3 Desktop Computer/Headphones

A standard Dell desktop computer was used to execute an application known as Synthetic Work 

Environment (SYNWORK) to present the arithmetic task. SYNWORK is a computer-based 

performance assessment tool that is capable of presenting up to four component subtasks 

(Elsmore, 1994). For this experiment, only the arithmetic subtask was presented (figure 4). In 

this task, participants were asked to add two randomly selected numbers. When the random 

numbers appeared on the screen, participants used a computer mouse to input the sum by 

clicking the “+” and “–” boxes below each digit of the default result. Upon completion of each 

problem, participants clicked the “Done” box to submit their answer to the current problem and 

to receive the next addition problem. The software recorded the number of correct problems, 

incorrect problems, and the average response time.
6

Figure 4. SYNWORK arithmetic task.

The desktop computer also generated a continuous tank noise that was provided to participants 

via Sony model MDR-7506 headphones. The continuous tank noise was used to mask the noise 

generated by the tactors to ensure that ratings of perceived urgency were based solely on the 

sense of touch and not the sense of hearing. The tank noise, recorded at the commander’s 

position in an M1A2 tank, was 50 dBA SPL, measured under the earcup of the participant’s 

headphones.

4.2.4 Questionnaire

Upon completion of each of the blocks, a post-block questionnaire was administered to gather 

each participant’s comments, opinions, and perception of the difficulty to identify tactile patterns 

(appendix B).

4.3 Experimental Design

A 2 × 2 × 2 × 4 within-subjects design was used with four independent variables: ISI, intensity, 

arithmetic task, and pattern. The independent variables and their associated levels are shown in 

table 2. Each participant completed eight blocks during the study. Each block lasted 10 minutes 

(min) and consisted of 64 trials or 64 random tactile pattern presentations. The order of 

presentation of the experimental blocks was counterbalanced using Williams squares.

Table 2. Independent variables and levels.

Variable Levels

Inter-Stimulus Interval 0 ms, 500 ms

Intensity 12 dB, 23.5 dB

Arithmetic Task provided, not provided

Pattern turn right, turn left, move forward, turn around
7

Four dependent variables measured: (1) ratings of perceived urgency of patterns, (2) the 

proportion of patterns detected, (3) the overall proportion of patterns correctly identified, and 

(4) ratings of difficulty of pattern identification. The proportion of patterns detected measured 

whether a pattern was perceived, regardless of whether it was identified correctly or not. For the 

overall proportion of patterns correctly identified, undetected patterns and incorrect identification 

were counted as errors.

4.4 Training

Each volunteer was briefed on the purpose of the investigation, the procedures to be followed 

during the study, and any risks involved in their participation. The investigator read the 

volunteer agreement affidavit aloud to the participant who followed along (appendix A) and 

addressed any questions the participant might have had regarding the study. If the volunteer 

agreed to take part in the investigation, he completed the information on the last page of the 

affidavit and signed it.

Next, each participant donned the tactile belt display (figure 5) and was seated in front of a 

desktop computer. They were then trained on both the tactile patterns and arithmetic task. For 

the tactile pattern training, participants were given a paper copy of the tactile patterns and 

received a brief explanation of each pattern. Participants were then provided each pattern several 

times to allow them to become familiar with how each tactile pattern felt. Next, the tactile 

patterns were provided in a random order, and the participant was asked to verbalize which 

pattern they received. The investigator informed participants if they made any identification 

errors. Once participants became 100% accurate in identifying tactile patterns, the investigator 

demonstrated the two ISI levels and the two intensity levels separately.
8

Figure 5. Participant donning tactile belt.

Upon completion of the tactile pattern training, the investigator demonstrated how to perform the 

arithmetic task. Next, the participants performed the arithmetic task for 2 min. Total training 

time lasted about 15 min for each participant.

4.5. Testing

During the experiment, each participant completed four blocks with the arithmetic task and four 

blocks without the arithmetic task. Participants were informed of whether or not the arithmetic 

task would be provided during each block. During each block, the participants verbally 

identified tactile patterns and indicated their perceived urgency level under various levels of 

stimulus intensity (12 dB and 23.5 dB) and ISI (0 ms and 500 ms). Ratings were based on a 

scale of 1 to 10, with 10 indicating extremely high urgency. Responses were recorded by the 

investigator. A typical response would be “Turn Right–7.” When the arithmetic distractor task 

was provided, participants performed the arithmetic task in addition to the detection, 

identification, and perceived urgency task. Participants were not told that either task was more 

important. During all experimental trials, participants listened to continuous tank noise to mask 

the noise of the tactors. Upon completion of each block, participants completed a questionnaire 

about the block that they received (see appendix B). This questionnaire allowed participants to 

rate how well they were able to identify tactile patterns and perform the arithmetic task. A 5 min 
9

break was given after each block of the data collection. Total time to complete the experiment 

was approximately 2 h.

5. Results

Separate analyses of variance (ANOVA) were conducted on the percentage of patterns detected 

and correctly identified, ratings of perceived urgency, and ratings of pattern identification 

difficulty. Statistical significance was concluded when p < 0.05. Significant effects were 

examined post hoc with the least significance difference (LSD) test. Means and standard error of 

the means are presented in figures 6–12. Descriptive statistics (means and standard error of the 

means) are presented in appendix C.

5.1 Perceived Urgency

The analysis of the ratings of perceived urgency revealed an Inter-Stimulus Interval × Intensity 

interaction, F(1, 15) = 23.128, p < 0.001, with main effects of both ISI, F(1, 15) = 19.418, 

p = 0.001 and intensity, F(1, 15) = 47.397, p < 0.001. No other main effects or interactions were 

found.

The Inter-Stimulus Interval × Intensity interaction is shown in figure 6. Post hoc analyses 

revealed that when patterns were presented at both the 12 dB and 23.5 dB intensities, ratings of 

perceived urgency were higher when the ISI was 0 ms than at 500 ms. This interaction can be 

attributed to the main effects of ISI and intensity. Ratings of perceived urgency were 

significantly higher when the ISI of patterns was 0 ms than at 500 ms. In regard to intensity, 

ratings of perceived urgency were significantly lower when patterns were presented at 12 dB 

than at 23.5 dB.
10

Figure 6. Inter-Stimulus Interval × Intensity interaction (rating of perceived urgency).

5.2 Percent Detected

The analysis of the percentage of patterns detected revealed an Inter-Stimulus Interval ×

Intensity interaction, F(1, 15) = 4.623, p = 0.048, with a main effect of intensity, F(1, 15) = 

7.816, p = .014. A significant Inter-Stimulus Interval × Pattern interaction, F(3, 45) = 3.824,

p = 0.016 was also indicated by the analysis. No other main effects or interactions were found.

The Inter-Stimulus Interval × Intensity interaction is shown in figure 7. Post hoc analyses 

revealed that when patterns were presented at an intensity of 23.5 dB, there was no significance 

in detection rates. However, when patterns were presented at an intensity of 12 dB, detection 

rates were higher when the ISI was 500 ms than at 0 ms. This interaction can be attributed to the 

main effect of intensity. A significantly greater percentage of patterns (1.32%) were detected 

when intensity was provided at 23.5 dB than at 12 dB. The Inter-Stimulus Interval × Pattern 

interaction is shown in figure 8. Post hoc analyses indicate that when the ISI was 500 ms, there 

was no significance in pattern detection rates. When the ISI was 0 ms, detection rates for “Move 

Forward” were significantly higher than “Turn Around.”
11

Figure 7. Inter-Stimulus Interval × Intensity interaction (percent detected).

Figure 8. Inter-Stimulus Interval × Pattern interaction (percent detected).
12

5.3 Overall Percent Correct

The analysis of the overall percentage of correctly identified patterns revealed an Inter-Stimulus 

Interval × Intensity interaction, F(1, 15) = 7.061, p = 0.018, and a significant Intensity × Pattern 

× Arithmetic interaction, F(3, 45) = 3.103, p = 0.036. Results showed a main effect of intensity 

F(1, 15) = 14.796, p = 0.002. No other main effects or interactions were found.

The Inter-Stimulus Interval × Intensity interaction is shown in figure 9. Post hoc analyses 

revealed that when patterns were presented at an intensity of 23.5 dB, there was no significance 

in the overall percentage of correctly identified patterns. However, when patterns were 

presented at an intensity of 12 dB, identification rates were higher when the ISI was 500 ms than 

at 0 ms. This finding is similar to the Inter-Stimulus Interval × Intensity interaction for 

detection. The Intensity × Pattern × Arithmetic interaction is shown in figures 10 and 11. Post 

hoc analyses indicate that when intensity was provided at 12 dB, for “Turn Around,” 

identification rates were significantly higher when the arithmetic was not provided than when the 

arithmetic was provided. However, identification rates for “Move Forward” were significantly 

lower when no arithmetic was provided than when it was provided. When intensity was 

provided at 23.5 dB, for “Turn Right,” identification rates were significantly higher when 

arithmetic task was provided than when it was not provided. These interactions can be attributed 

to the main effect of intensity. A significantly lower percentage of patterns (2%) were correctly 

indentified when intensity was provided at 12 dB than at 23.5 dB.

Figure 9. Inter-Stimulus Interval × Intensity interaction (overall percent correct).
13

Figure 10. Intensity (12 dB) × Pattern × Arithmetic interaction (overall percent correct).

Figure 11. Intensity (23.5 dB) × Pattern × Arithmetic interaction (overall percent correct).
14

5.4 Identification Difficulty

Analysis of the ratings of the difficulty to identify patterns revealed a significant main effect of 

arithmetic, F(1, 14) = 6.512, p = 0.023. Ratings of difficulty were significantly higher when 

arithmetic was provided (figure 12).

Figure 12. Mean rating of pattern identification difficulty by arithmetic.

6. Discussion

Although the use of tactile patterns has been successfully used to communicate messages, there 

may be a need to provide levels of priority or some sense of urgency to those patterns to enhance 

the information management of Soldiers. In an effort to maximize the benefits of tactile displays 

for Soldiers, it is essential that the manipulation of parameters such as frequency, intensity, 

duration, and ISI be explored. The objective of this study was to quantify the effects of ISI and 

stimulus intensity on perceived urgency and on the detection and identification of tactile patterns. 

Findings of this study will be discussed in light of the dependent variables and the hypotheses.

In regard to ratings of perceived urgency, intensity and ISI both had an effect on how 

participants rated the urgency of tactile patterns. Data from the Inter-Stimulus × Intensity 

interaction indicate that patterns provided at with no ISI at the strong 23.5 dB intensity were 

rated the most urgent, and patterns with the 500 ms ISI at the 12 dB intensity were rated the least 

urgent. These findings support our hypotheses regarding ratings of perceived urgency. 

Although patterns provided with the 500 ms ISI at the 12 dB intensity were rated the least urgent, 

these patterns provided for higher detection and identification rates than patterns provided with 
15

no ISI at the 12 dB intensity. Apparently these patterns were not as easily missed because they 

had a longer total duration, which made them more distinct than the patterns with no ISI. These 

findings are similar to those obtained for these parameters (intensity and ISI) in auditory display 

research. Auditory signals with shorter inter-pulse intervals and higher sound intensity pressure 

levels yielded greater perceived urgency (Haas and Edworthy, 1996; Haas and Casili, 1995).

It is important that users of tactile display systems are able to detect tactile stimuli regardless of 

the type of environment in which the stimuli is provided. In this investigation, detection rates 

were better when tactile patterns were provided at the strong 23.5 dB intensity than at the weaker 

12 dB intensity. Data from the Inter-Stimulus Interval × Intensity interaction indicate that when 

tactile patterns were provided at the greater 23.5 dB intensity, ISI had no effect on detection 

rates. However, tactile patterns were more difficult to detect when they were provided at the 

weak 12 dB intensity with no ISI. It appears that patterns with no ISI or shorter total duration 

time were more easily missed when they were provided at the weaker intensity. The InterStimulus Interval × Pattern interaction indicates that when no ISI was provided, it was more 

difficult to detect the “Turn Around” pattern than the “Move Forward” pattern. This finding may 

be explained by the shorter total duration time of patterns provided with no ISI and the difference 

in sensitivity thresholds for the belly and the back. For the “Move Forward” pattern, the 

sequence in which the tactors vibrate begins on the sides of the body and sweep toward the belly, 

and for the “Turn Around” pattern, the sequence begins on the sides and sweep toward the back. 

All participants in this investigation were male, and for males, the sensitivity thresholds on the 

back are slightly higher than the belly (Weinstein, 1968). Although significant effects were 

found, detection results were very high (97% and above) in this investigation.

In addition to users being able to detect tactile stimuli, it is important that users are able to 

distinguish or identify tactile stimuli as well. Similar to the detection findings, identification 

rates were better when tactile patterns were provided at the strong 23.5 dB intensity than at the 

weaker 12 dB intensity. The analysis also revealed a similar Inter-Stimulus Interval × Intensity 

interaction. ISI had no effect on identification rates at the strong 23.5 dB, but identification rates 

were lower when tactile patterns were provided with no ISI at the weak 12 dB intensity. This 

finding can be explained in the same way as the Inter-Stimulus Interval × Intensity interaction 

for detection. Data from the Intensity × Pattern × Arithmetic interaction indicate that when 

patterns were provided at the strong 23.5 dB intensity, identification rates were better when 

arithmetic task was provided than when it was not provided for “Turn Right.” When tactile 

patterns were provided at the weak 12 dB intensity, identification rates were better when the 

arithmetic was not provided than when the arithmetic was provided for “Turn Around.” 

Although identification rates were not significantly better for all patterns when the arithmetic 

was not provided as opposed to when it was provided, these findings partially support the 

hypothesis that states that detection and identification rates would be degraded when the 

arithmetic task was provided. However, on the contrary, identification rates for “Move Forward” 

were worse when no arithmetic was provided than when it was provided. Providing an 
16

explanation for this finding is rather difficult because it is unclear why this occurred. Significant 

effects were found in identification rates. However, results were very high (95% and above) in 

this study

In regard to the hypothesis that states that detection and identification rates would be degraded 

when the arithmetic distractor task was provided, the arithmetic distractor task did not degrade 

detection and identification rates. However, questionnaire results indicate that participants felt 

that it was harder to identify tactile patterns when the arithmetic distractor task was provided.

7. Conclusions and Future Work

Results of the present study show that the manipulation of ISI and intensity are a feasible means 

of adding a sense of urgency to tactile patterns. Despite the significance among the detection 

and identification findings, these findings are not very meaningful from a practical perspective 

since the results were so high. Therefore, it is difficult to identify one urgency level as more 

favorable than the other in the investigation. Adding this level of complexity to tactile patterns 

or messages will enhance the information management of Soldiers by allowing them to prioritize 

the tasks within their overall mission. This laboratory investigation was the first step in 

empirically determining the ability of Soldiers to detect and identify tactile patterns with varying 

urgency levels. However, this research should be extended to the field so that it encompasses 

more demanding, operationally relevant tasks such as performing dismounted maneuvers or 

riding in a vehicle. Greater significant effects are expected in the field. Also, a more in depth 

look should be taken at the number of levels of urgency and the number of patterns that are 

perceivable in Army relevant environments.
17

8. References

Brewster, S.; Brown, L. M. Tactons: Structured Tactile Messages for Non-Visual Information 

Display. Proceedings of the 5th Australasian User Interface Conference (AUIC2004),

Duniden, New Zealand, 2004; Vol. 28, pp15–23.

Brown, L. M.; Brewster, S. A.; Purchase, H. C. Multidimensional Tactons for Non-Visual 

Information Presentation in Mobile Devices. Proceedings of the Eigth Conference on

Human-Computer Interaction with Mobile Devices and Services, Helsinki, Finland, 2006; 

Vol. 159, pp 231–238.

Cholewiak, R. W.; Brill, J. C.; Schwab, A. Vibrotactile Localization on the Abdomen: Effects of 

Place and Space. Perception and Psychophysics 2004, 66 (6), 970–987.

Elsmore, T. F. SYNWORK1: A PC-based Tool for Assessment of Performance in a Simulated 

Work Environment. Behavior Research Methods, Instruments, & Computers 1994, 26 (4), 

421–426.

Gilson, R. D.; Redden, E. S.; Elliott, L. R. Remote Tactile Displays for Future Soldiers; ARLSR-0152; U.S. Army Research Laboratory: Aberdeen Proving Ground, MD, 2007.

Haas, E. C.; Casali, J. G. Perceived Urgency and Response Time to Multi-tone and Frequencymodulated Warning Signals in Broadband Noise. Ergonomics 1995, 38 (11), 2313–2326.

Haas, E. C.; Edworthy, J. Designing Urgency into Auditory Warnings Using Pitch, Speed and 

Loudness. Computing & Control Engineering Journal 1996, 7 (4), 193–198.

Jones, L. A.; Sarter, N. B. Tactile Displays: Guidance for Their Design and Application. Human 

Factors 2008, 50, 90–111.

Jones, L. A.; Lockyer, B.; Piateski, E. Tactile Display and Vibrotactile Pattern Recognition on 

the Torso. Advanced Robotics 2006, 20 (12), 1359–1374.

Krausman, A. S.; White, T. L. Tactile Displays and Detectability of Vibrotactile Patterns as 

Combat Assault Maneuvers are Being Performed; ARL-TR-3998; U.S. Army Research 

Laboratory: Aberdeen Proving Ground, MD, 2006.

Krausman, A. S.; White, T. L. Detection and Localization of Vibrotactile Signals in Moving 

Vehicles; ARL-TR-4463; U.S. Army Research Laboratory: Aberdeen Proving Ground, MD, 

2008. 
18

Merlo, J. L.; Terrence, P. I.; Stafford, S.; Gilson, R. D.; Hancock, P. A.; Redden, E. S.; 

Krausman, A.; Carstens, C. B.; Pettitt, R.; White, T. L. Communicating Through the Use of 

Vibrotactile Displays for Dismounted and Mounted Soldiers. Proceedings of the 25th Army 

Science Conference, Orlando, FL, 2006. 

Pettitt, R. A.; Redden, E. S.; Carstens, C. B. Comparison of Army Hand and Arm Signals to a 

Covert Tactile Communication System in a Dynamic Environment; ARL-TR-3838; U.S. 

Army Research Laboratory: Aberdeen Proving Ground, MD, 2006.

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J.B.F. & Self, B.P., Eds.; In Tactile Displays for Orientation, Navigation and 

Communication in Air, Sea, and Land Environments (RTO-TR-HFM-122). Research and 

Technology Organisation and North Atlantic Treaty Organisation: Neuilly-sur-Seine Cedex, 

France, 2008; pp 1-1–1-18. 

Weinstein, S. Intensive and Extensive Aspects of Tactile Sensitivity as a Function of Body Part 

Sex, and Laterality. In The Skin Senses; Kenshalo, D. R., Ed.; Charles C. Thomas, 

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19

Appendix A. Volunteer Agreement Affidavit

Informed Consent Form 

Army Research Laboratory, Human Research & Engineering Directorate

Aberdeen Proving Ground, MD 21005

Title of Project: The Effects of Stimulus Intensity and Inter-Stimulus Duration on 

Perceived Urgency and the Ability to Detect and Identify Tactile Patterns

Project Number: ARLSponsor: Army Research Laboratory

Principal Investigator: Timothy L. White

Army Research Laboratory

Human Research & Engineering Directorate

RDRL-HRS-B, Bldg. 459

Aberdeen Proving Ground, MD 21009

(410) 278-5884; timothy.l.white1@us.army.mil

Associate Investigator: Andrea S. Krausman

Army Research Laboratory

Human Research & Engineering Directorate

RDRL-HRS-B, Bldg. 459

Aberdeen Proving Ground, MD 21009

(410) 278-5933; andrea.krausman@us.army.mil

You are being asked to join a research study. This consent form explains the research study and 

your part in it. Please read this form carefully before you decide to take part. You can take as 

much time as you need. Please ask the research staff any questions at any time about anything 

you do not understand. You are a volunteer. If you join the study, you can change your mind 

later. You can decide not to take part now or you can quit at any time later on.

 

This appendix appears in its original form, without editorial change.
20

Purpose of the Study

The purpose of this study is to assess the effects of urgency on the detection and identification of 

tactile patterns. You are being invited to participate because you are in good health and are not 

taking medications for any health reasons

Procedures to be Followed

You will be asked to (1) to detect and identify tactile patterns and rate their urgency and (2) to 

perform an arithmetic task. Tactile patterns will be provided with a belt that will be worn around 

your waist on the outside of your shirt, and the arithmetic task will be presented on a computer 

screen. Before the testing period, you will be trained on the tactile patterns and the arithmetic 

task. 

There will be a total of eight blocks in this experiment. Each block will last 10 minutes. In four 

of the blocks, you will only identify tactile patterns and provide an urgency rating of those 

patterns. In the other four blocks, you will perform an arithmetic task in addition to the pattern 

identification and urgency rating task. You will rate the urgency of the tactile patterns you 

receive on a scale of 1 to 10, with 10 indicating an extremely urgent pattern. Random tactile 

patterns will be presented with varying intensity and inter-stimulus intervals during each block. 

When tactile patterns are received, you will be asked to verbalize the tactile pattern received and 

rate its urgency (for example: “Turn Right – 7”). There will be 64 trials per block for a total of 

512 trials to complete the experiment.

After each block, you will be asked to complete a questionnaire to rate how well you were able 

to identify tactile patterns and perform the arithmetic task (if provided). You will be given the 

opportunity to rest for 5 minutes after each block. The investigator will record any comments 

that you may have during this investigation. 

Discomforts and Risks

The risks to you in this experiment are considered minimal. They are not unlike those to which

you might be exposed when reading a standard computer screen. These risks might include 

headaches and eye strain associated with observing the visual display.

Benefits

There are no personal benefits for you for taking part in this study. However, your participation 

will provide valuable information about Soldier performance that will assist in the design of 

future Army systems.
21

Duration

It will take approximately 2 hours for you to take part in this study.

Confidentiality

Your participation in this research is confidential. The data will be stored and secured at 

Aberdeen Proving Ground, in a locked file cabinet. The data, without any identifying 

information, will be transferred to a password-protected computer for data analysis. After the 

data is put in the computer file, the paper copies of the data will be shredded. This consent form 

will be sent to Army Research Laboratory’s Institution Review Board, where it will be retained 

for a minimum of three years. 

If the results of the experiment are published or presented to anyone, no personally identifiable 

information will be shared. Publication of the results of this study in a journal or technical 

report, or presentation at a meeting, will not reveal personally identifiable information. The 

research staff will protect your data from disclosure to people not connected with the study. 

However, complete confidentiality cannot be guaranteed because officials of the U. S. Army 

Human Research Protections Office and the Army Research Laboratory’s Institutional Review 

Board are permitted by law to inspect the records obtained in this study to insure compliance 

with laws and regulations covering experiments using human subjects.

We would like your permission to take pictures during the experimental session. The pictures 

will be printed in technical reports and shown during presentations when we describe the results 

of the study. To protect your identity, we will pixelate the image to obscure your face. You can 

still be in the study if you prefer not to be photographed. Please indicate below if you will agree 

to allow us to take pictures of you.

I give consent to be photographed during this study: ____Yes ____No 

please initial:____

Contact Information for Additional Questions

You have the right to obtain answers to any questions you might have about this research both 

while you take part in the study and after you leave the research site. Please contact anyone 

listed at the top of the first page of this consent form for more information about this study. You 

may also contact the Chairperson of the Human Research & Engineering Directorate, Institution 

Review Board, at (410) 278-5992 with questions, complaints, or concerns about this research, or 

if you feel this study has harmed you. The chairperson can also answer questions about your 

rights as a research participant. You may also call the chairperson’s number if you cannot reach 

the research team or wish to talk to someone else.
22

Voluntary Participation

Your decision to be in this research is voluntary. You can stop at any time. You do not have to 

answer any questions you do not want to answer. Refusal to take part in or withdrawing from this 

study will involve no penalty or loss of benefits you would receive by staying in it.

Military personnel cannot be punished under the Uniform Code of Military Justice for choosing 

not to take part in or withdrawing from this study, and cannot receive administrative sanctions 

for choosing not to participate.

Civilian employees or contractors cannot receive administrative sanctions for choosing not to 

participate in or withdrawing from this study.

You must be 18 years of age or older to take part in this research study. If you agree to take part 

in this research study based on the information outlined above, please sign your name and the 

date below. 

You will be given a copy of this consent form for your records.

This consent form is approved from to .

Do not sign after the expiration date of 

_____________________________________ ___________________

Participant Signature Date

______________________________________________ ___________________

Person Obtaining Consent Date
23

Appendix B. Post-Block Questionnaire

Post-Block Questionnaire

Participant #: ___ Block ___ Arithmetic Yes or No

Answer each question below by placing an “X” in the bracket that best describes your 

experience in the experimental block you just completed. 

Please answer the following question.

1. How difficult or easy was it to identify the tactile patterns and their urgency levels.

 Neither 

Extremely Difficult Nor Extremely

 Difficult Easy Easy

 [ ] [ ] [ ] [ ] [ ] [ ] [ ]

Comment: _____________________________________________________________

If you received the arithmetic task in your last block, please answer the following question.

2. How difficult or easy was it to perform the arithmetic task.

 Neither 

Extremely Difficult Nor Extremely

 Difficult Easy Easy

 [ ] [ ] [ ] [ ] [ ] [ ] [ ]

Comment: _____________________________________________________________

 

This appendix appears in its original form, without editorial change. 
24

INTENTIONALLY LEFT BLANK.
25

Appendix C. Descriptive Statistics (Means and Standard Error of the 

Means[SEM])

Percent Detected

Intensity

Intensity Mean SEM

12 dB 98.05 0.274

23.5 dB 99.37 0.164

Inter-Stimulus Interval (ISI) x Intensity

ISI Intensity Mean SEM

0 ms 12 dB 97.51 0.448

23.5 dB 99.17 0.287

500 ms 12 dB 98.58 0.314

23.5 dB 99.56 0.161

Inter-Stimulus Interval x Pattern

ISI Pattern Mean SEM

0 ms Turn Right 98.73 0.502

Turn Left 97.95 0.613

Move Forward 99.12 0.348

Turn Around 97.56 0.623

500 ms Turn Right 99.51 0.257

Turn Left 98.63 0.406

Move Forward 98.83 0.384

Turn Around 99.32 0.350

Overall Percent Correct

Intensity

Intensity Mean SEM

12 dB 96.00 0.389

23.5 dB 98.61 0.229

 

This appendix appears in its original form, without editorial change. 
26

Inter-Stimulus Interval x Intensity

ISI Intensity Mean SEM

0 ms 12 dB 95.12 0.627

23.5 dB 98.68 0.323

500 ms 12 dB 96.88 0.458

23.5 dB 98.54 0.325

Intensity x Pattern x Arithmetic 

Intensity Pattern Arithmetic Mean SEM

12 dB Turn Right No 98.05 0.595

Turn Left No 95.51 1.158

Move Forward No 94.53 1.357

Turn Around No 97.66 0.704

Turn Right Yes 96.29 1.041

Turn Left Yes 94.53 1.385

Move Forward Yes 97.27 0.887

Turn Around Yes 94.14 1.344

23.5 dB Turn Right No 99.61 0.275

Turn Left No 99.02 0.430

Move Forward No 99.80 0.195

Turn Around No 99.61 0.275

Turn Right Yes 96.68 1.051

Turn Left Yes 96.68 1.014

Move Forward Yes 99.02 0.430

Turn Around Yes 98.44 0.772

Ratings of Perceived Urgency

Inter-Stimulus Interval

ISI Mean SEM

0 ms 4.74 0.044

500 ms 3.66 0.034

Intensity

Intensity Mean SEM

12 dB 2.90 0.029

23.5 dB 5.51 0.039

Inter-Stimulus Interval x Intensity
27

ISI Intensity Mean SEM

0 ms 12 dB 3.24 0.047

23.5 dB 6.25 0.056

500 ms 12 dB 2.55 0.034

23.5 dB 4.78 0.048

Ratings of Identification Difficulty

Arithmetic

Arithmetic Mean SEM

No 3.13 0.196

Yes 3.75 0.193
NO. OF

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