Time perception has been shown to be modulated by various stimulus features such as emotion, color, etc. In addition, more recent studies have documented that temporal perception is also affected by task-irrelevant, non-temporal stimulus properties such as number and size. More specifically, the stimulus of large magnitude is judged to last longer than a stimulus of smaller magnitude. Such cross-domain magnitude interaction has been explained by A Theory of Magnitude (ATOM). According to ATOM, magnitudes such as space, time, and quantities are processed through a generalized magnitude system. ATOM posits that task-irrelevant magnitudes interfere with the processing of task-relevant magnitudes as all the magnitudes are processed in a common system. Many behavioural and neuroimaging studies have found support in favour of a common magnitude processing system. However, it is largely unknown whether such cross-domain monotonic mapping arises from a change in accuracy of the magnitude judgments or results from changes in precision of the processing of magnitude. Therefore, in the present study, we examined whether large numerical magnitude affects temporal accuracy or temporal precision or both. In other words, whether numerical magnitudes change our temporal experience or simply bias our duration judgments. Participants performed a duration discrimination task for the two sequentially presented magnitudes. The first magnitude (standard) was 5 and had a fixed duration of 550ms and the second magnitude (comparison) was either 1 , 5, or 9 presented with varying durations from 250 to 850ms in steps of 100ms. Participants were asked to judge whether the comparison magnitude lasted longer or shorter than the standard magnitude. We estimated temporal accuracy (PSE) and precision (Weber ratio) for each numerical magnitude. The estimated PSE and Weber ratio data were submitted to a one-way repeated measures ANOVA to test how numerical magnitudes affected temporal perception and temporal precision. The ANOVA results revealed that temporal accuracy (PSE) for large (9) numerical magnitude was significantly lower than that of small (1) and identical (5) magnitudes. This implies that the temporal duration was overestimated for large (9) numerical magnitude compared to small (1) and identical (5) numerical magnitude. However, no influence of numerical magnitude was observed on temporal precision (Weber ratio). The findings of the present study suggest that task-irrelevant numerical magnitude selectively affects the accuracy of processing of duration but not duration discrimination.
ANUJ SHUKLA
Bapi Raju