Figure 1
Experiment set-up. (a) Training reference duration (approximately 2 min). After a 5 s fixation cross, participants viewed a flashing white circle ten times with a random inter-trial interval (1–1.5 s) to learn the reference duration of (450 ms). (b) An example trial of the duration judgment task. The probe circle was selected from 300, 350, 400, 450, 500, 550, or 600 ms, followed by a monetary incentive cue of 1 s in either the blue, red, or gray color with a random fixation (2–2.5 s) in between. Participants responded to the decision probe within a 2 s time limit. They pressed a mouse button to indicate that the perceived probe duration was longer or shorter than the reference duration. Each trial was scored on a Likert scale from 1 (0% confident) to 7 (100% confident) to obtain a confidence score.
Figure 2
Result of reward influence on time perception. Probability of responses in which participants reported that the target duration lasted longer than the reference (450 ms) plotted as a function of the display duration for each reward condition, separately (gain, neutral, and loss). The points of subjective equality (PSE) are shifted to the left in the gain and loss conditions compared to the neutral condition. The PSE for reward conditions shows a significant difference between gain and neutral (top right). The slope values of the fitted psychometric function show a non-significant difference between gain and neutral (bottom right). (Note: bar graphs show mean and standard error).
Figure 3
Reward influence on reaction time and confidence. (a) Mean values of reaction time across all probe durations, except for 450 ms, are shown on the left, while mean values of reaction time perceived as longer for 450 ms are shown on the right. (b) Mean confidence scores for all probe durations, except for 450 ms, are depicted on the left, and mean values of confidence ratings perceived as longer only for 450 ms are presented on the right. (The 450 ms is plotted separately since it is equal to the reference duration and no correct response is given for this duration).
Figure 4
Comparing confidence scores and reaction times: High vs. Low Confidence Groups. (a) Group differences in confidence scores between LC and HC participants for 450 ms and correct answers. (b) Group differences in reaction times between LC and HC participants for 450 ms and correct answers. (Note: bar graphs are plotted based on the mean and standard error).
Figure 5
Effect of reward gain on time perception within HC and LC groups. Comparison of PSEs between gain and neutral conditions within HC (a), and LC (b) groups are plotted with corresponding psychometric functions. The PSE is shifted to the left in the gain compared to neutral condition only in HC group, not in LC group. Comparison of the mean of PSEs between gain and neutral shows significant difference in HC group (a). (Note: bar graphs are plotted based on the mean and standard error).
Figure 6
Effect of reward gain on time perception between HC and LC groups. Comparison of PSEs between the HC and LC groups in the gain condition are plotted with corresponding psychometric functions. The PSE is shifted to the left in the HC compared to LC group. The comparison of the means of PSEs between the HC and LC groups indicates significant difference in between groups. (Note: bar graph is plotted based on the mean and standard error).
Figure 7
Correlation between confidence and time perception. (a) Pearson correlation (one-tail) between confidence (450 ms) and PSE in the gain condition. (b) Pearson correlation (one-tailed) between confidence (correct answers) and PSE in the gain condition.