The sense of agency refers to the experience of "I am the initiator of actions, controlling the external world". Temporal binding, which is related to the sense of agency, refers to the subjective compression of the perceived time interval between voluntary action and its action outcome. Previous studies have explored the effect of emotional valence on temporal binding by setting the predictability of emotional valence as the control variable. However, the effect of the predictability of emotional valence on temporal binding remains unknown. This study explored the effect of the predictability of emotional valence of action outcomes on temporal binding, based on the hypothesis that temporal binding is stronger when emotional valence is more predictable.
This study used Libet’s clock paradigm to investigate the effect of the predictability of emotional valence of action outcomes on temporal binding. A 2 (predictability of emotional valence, within: predictable vs. unpredictable) × 2 (stimulus modality, between: auditory vs. visual) mixed design was employed. A total of 60 participants were randomly assigned to one of two between-subject conditions, resulting in 30 in the auditory group and 30 in the visual group. There were two main phases of the study. During the baseline phase, the participants in the two groups were asked to either press the key at a freely chosen point from 2,560ms to 5,120ms or perceive the auditory/visual stimulus randomly from 2,560ms to 5,120ms after the trial start. Next, they were asked to estimate the position of the clock hand at the onset of either the key-press or the stimulus. During the operant phase, participants were also asked to press the key at a freely chosen point from 2,560ms to 5,120ms. The key-press would cause the auditory/visual emotional outcome (negative, neutral or positive) following a delay duration of 250ms. Next, they were asked to estimate the position of the clock hand at the onset of either the key-press or the emotional outcome. When the emotional valence was predictable, there would be a fixed emotional outcome to the key-press (negative, neutral or positive) in 80% of trials and the other remaining emotional outcome in 20% of trials. When the emotional valence was unpredictable, the key-press would result in one of the three emotional outcomes.
The results showed that temporal binding was enhanced when the emotional valence was predictable. Furthermore, when emotional valence was predictable, the outcome binding was stronger in both the auditory and visual groups, whereas the action binding was stronger only in the visual group.
In conclusion, the predictability of emotional valence is an important factor affecting temporal binding. The predictability of emotional valence can enhance outcome binding in both auditory and visual modalities, but can only enhance action binding in the visual modality. This may be due to the difference between action and outcome binding mechanisms or between the timing systems of auditory and visual stimuli. These results have an important implication for the interactive design of Advanced Driver Assistance Systems (ADAS) since temporal binding is the main index of the sense of agency.