The author has declared that no competing interests exist.
Conceived and designed the experiments: YM. Performed the experiments: YM. Analyzed the data: YM. Contributed reagents/materials/analysis tools: YM. Wrote the paper: YM.
In daily life, huge costs can arise from just one incorrect performance on a visual search task (e.g., a fatal accident due to a driver overlooking a pedestrian). One potential way to prevent such drastic accidents would be for people to modify their decision criterion (e.g., placing a greater priority on accuracy rather than speed) during a visual search. The aim of the present study was to manipulate the criterion by creating an awareness of being watched by another person. During a visual search task, study participants were watched (or not watched) via video cameras and monitors. The results showed that, when they believed they were being watched by another person, they searched more slowly and accurately, as measured by reaction times and hit/miss rates. These findings also were obtained when participants were videotaped and they believed their recorded behavior would be watched by another person in the future. The study primarily demonstrated the role of being watched by another on the modulation of the decision criterion for responding during visual searches.
In daily life, huge costs can arise from just one failing performance during what is essentially a visual search task (e.g., a fatal accident due to a driver overlooking a pedestrian, or an airline hijacking resulting from overlooking dangerous materials during baggage screening). A potential way to prevent such drastic costs would be to shift the decision criterion during the visual search. In the car driving situation, for example, the potential for an accident could be decreased by making a slower, more careful search in favor of speed or quickness. The principal aim of the present study was to manipulate the decision criterion for responding during visual searches by creating an awareness of being watched by another person.
People are highly sensitive to the signals of being watched
To date, no study has investigated the role of the being watched by another person on the modulation of a decision criterion in a non-social context. This study examines whether an awareness of being watched affects participants' performances during visual searches. There are two plausible hypotheses as to the criterion shift during visual searches with reference to a speed-accuracy tradeoff
In summary, the present study examines the effect of being watched by another person during visual searches. If the first hypothesis is supported, reaction times (RT) will be faster and errors more frequent under the condition of being watched (watched condition) than the condition of being unwatched (unwatched condition). If the second hypothesis is supported, RTs will be longer and errors fewer under the watched than the unwatched condition.
Seventy-three paid graduates and undergraduates participated in the present experiments. There were 24 participants in
Ethical approval for this study was obtained from the Research Ethics Committee of the School of Psychology in Chukyo University. All participants provided written informed consent. They gave permission to use their data in the analysis.
The visual stimuli were projected on a 17 inch CRT monitor (BenQ G775 with a resolution of 1024×768 and refresh rate of 60 Hz). To collect the RTs, we used a response time box
There were two within-participant factors: being watched (watched condition, unwatched condition) and target presence on the visual search task (target present trials, target absent trials), which were crossed to yield four conditions.
In the watched condition (top on
(A) The top picture represents the watched condition and the bottom picture represents the unwatched condition. (B) An example of the target present trials. Participants were required to search for a T in any orientation from among offset Ls in any orientation. The salt-and-pepper visual noise (bottom picture) was superimposed on the search display (top picture).
In the unwatched condition (bottom on
The search display consisted of 16 stimuli, a central fixed indicator (a cross), and salt-and-pepper visual noise (
The experiment was composed of four sessions (two watched and two unwatched conditions). To counterbalance the order of the being watched or not, 12 participants had sessions in the following order: watched–unwatched–watched–unwatched, and then the remaining 12 participants experienced the reverse order. The first and second sessions were practice sessions and were not included in the statistical analyses. Each session began with 18 practice trials with correct/incorrect feedback after each response prior to 72 test trials, half of which were target present trials. In order to induce inaccurate performances, the participants were not provided feedback during the 72 test trials, and the preceding 18 practice trials were excluded from statistical analysis.
Each session started when participants pressed a response button on an instruction screen. After a fixed cross was presented on the center of the display for 1,000 ms, the search display appeared, and remained until a response was made or for 10,000 ms. The participants were instructed to make a target present or absent judgment by using two response buttons, as quickly and accurately as possible. Twelve participants were required to press the left button for a target present judgment, and the right button for target absent; the remaining twelve participants had the reverse setup (left button for target absent and right button for target present). After the response selection or 10,000 ms, the next trial began. In the preceding 18 practice trials, visual correct/incorrect feedback was provided at the center of the display after the response selection or 10,000 ms. The participants were instructed to maintain the viewing distance (57 cm), although they were free to move their heads. The experiment was conducted in a well-lighted room (horizontal illuminance on the desk was approximately 620 lx).
Trials in which the participants did not make a response for 10,000 ms were removed from the statistical analyses (0.52% of trials were removed). Errors during visual searches were divided into groups: “miss” (target absent judgment when target present) and “false-alarm” (target present judgment when target absent).
Trials on which the participants made an error were discarded from RT analysis. Means of RTs under the target present and absent trials are shown in
(A)–(D) Results in
Since the means of false-alarm rates (number of false-alarm trials divided by the total number of the target present trials) were extremely low and did not vary much between conditions (2.18% of watched and 1.68% of unwatched), we focused only on the miss rates.
The means of miss rates (number of miss trials divided by the total number of the target absent trials) are shown in
For each participant and for each condition,
The results indicated that the participants searched more slowly and accurately when they thought they were being watched by another person, supporting the second hypothesis: the participants prioritized accuracy. In addition, with reference to signal detection theory, it found that the effect of being watched did not alter the sensitivity (
To further test the effect of being watched during visual searches, in
The apparatus was identical to
There were two within-participant factors: being videotaped (videotaped condition, non-videotaped condition) and target presence on the visual search task (target present trials, target absent trials), which were crossed to yield four conditions.
In the videotaped condition, participants were videotaped by the DV cameras during the session. In the non-videotaped condition, the two DV cameras were covered by opaque fabrics and were not operated. The locations of the DV cameras were the same as for
The stimuli were identical to
The procedure was almost identical to
Trials on which the participants did not make a response for 10,000 ms were removed from the statistical analyses (0.75% of trials were removed).
Trials in which the participants made an error were discarded from RT analysis. The means of RTs for the target present (or absent) trials are shown in
The means of false-alarm rates were extremely low and did not vary systematically with each condition (2.63% for the watched condition and 3.31% for the unwatched condition).
The means of miss rates are shown in
Where necessary, the proportions of 1 and 0 were adjusted to avoid infinite values. For the means of
The results indicated that the participants searched more slowly and accurately when they were being videotaped and they believed their behavior would be watched in future. Results also indicated that the non-real-time signals of being watched also affected the decision criterion during visual searches. Taken together, the results of Experiments 1 and 2 showed that the signals of being watched by another person, whether in real time or in the future, contribute significantly to a decision criterion shift of prioritizing accuracy over speed during visual searches.
However, these conclusions have one caveat: The slower RTs and fewer misses under the watched (or videotaped) condition might be a part of the post-search process rather than the search process (i.e., the participants were careful in making their response selection, after the visual search). The next experiment was conducted to examine this possibility. In
If the finding that participants searched more slowly and accurately when they were being watched was derived from the change in the search process, then the slope of the search function would be steeper under the watched condition compared to the unwatched condition.
The apparatus was identical to
There were three within-participant factors: being watched (watched condition, unwatched conditions), set size (stimulus search set size of 4, 16), and target presence on visual search task (target present trials, target absent trials), which were crossed to yield eight conditions.
The stimuli were identical to
The procedure was identical to
As before, trials on which the participants did not make a response for 10,000 ms were excluded from statistical analyses (0.17% of trials were removed).
Trials in which participants made an error were discarded from RT analysis. The means of RTs in the target present (or absent) trials are shown in
A three-way repeated measures ANOVA revealed a significant main effect of being watched (
The slope and
(A) Means of search function's slope (in ms/item) in the target present trials. (B) Means of the slope in the target present trials. (C) Means of search function's
Finally, to confirm that outliers did not cause the difference in RTs and the slope, the statistical analyses were also conducted by using the trimmed means of RTs. Since the overall patterns of statistical results were similar to the results using non-trimmed RT means, we rejected the possibility that outliers influenced the differences in RTs.
The means of false-alarm rates were extremely low and did not vary systematically with each condition (2.13% and 2.38% for set sizes of 4 and 16, respectively, in the watched condition, and 1.88% and 2.57% for set sizes of 4 and 16 in the unwatched condition).
The means of miss rates are shown in
Where necessary, the proportions of 1 and 0 were adjusted to avoid infinite values. For the means of
The results showed that the slope of the search function was steeper for the watched condition than the unwatched condition, but the
The overall aim of the present study was to manipulate the decision criterion during visual searches by making participants aware of being watched by another person. Experiments 1 and 3 showed that participants searched more slowly and accurately when they were being watched (compared to when they were unwatched) by another person. Although it has already been shown that the signals of being watched (or observed) affect participants' criteria for making a decision on social tasks (e.g.,
Experiment 2 showed that participants searched more slowly and accurately when they were being videotaped, and they believed their recorded behavior would be watched by another person in the future. Also, a decision criterion shift during visual searches was induced by non-real-time signals of being watched. The results of Experiment 2 have significant implications with regard to the car driving example, given above; installing in-vehicle cameras and being videotaped at all times during driving could contribute to a driver's more careful visual searching. Although this most likely would be considered impractical on a widespread basis, it may be of interest to transportation companies, i.e., employers of truck drivers, bus drivers, etc.
In comparison to the present study using video-monitoring setups for the condition of being watched, more subtle cues of being watched (e.g., eye-like paintings or dots:
Finally, three potential problems in the present study need to be mentioned. Firstly, we imposed a considerably difficult search task on the participants; salt-and-pepper visual noise was superimposed on the search display and knowledge of results feedback was not provided after each response during test trials to induce inaccurate performance. Therefore, the decision criterion shift during visual searches when the participants were being watched by another might be limited to the difficultly of the search task (e.g., similar to searching for a man wearing a dark suit while driving a car in the rain). It is suggested that future studies should investigate this issue by manipulating the level of task difficulty. Next, in the visual search task in
In conclusion, the present study primarily demonstrated the role of being watched on the modulation of a decision criterion during visual searches. Of course, the author does not suggest that people need to perform searches slowly and accurately in all circumstances. However, some visual searches ideally should be performed as carefully as possible to prevent fatal accidents and huge costs associated with possible visual search failures. The results of this study could have a significant impact under the condition that people should search carefully.