Task-relevant attention and repetition suppression co-determine perceived duration

Abstract

Duration perception of an event can be influenced by the temporal context. One such phenomenon is subjective time expansion induced in an oddball paradigm ("oddball chronostasis"), where the duration of a novel item (oddball) appears longer than that of repeated items (standards). Two leading theories are 1) attention enhances oddball duration [Tse et al., 2004] and 2) repetition suppression reduces standards duration [Pariyadath & Eagleman, 2007]. However, no studies so far have evaluated both together. We thus measured observers' chronostasis magnitude (CM) with constant stimuli method, where CM = standard duration - point of subjective equality of the target, and manipulated three sequences types: repeated, ordered and random (Fig 1a). The stimuli dimensions were digits, orientations, and colors in Exp 1, 2, and 3, respectively (Fig 1b-d). The repeated condition was the classic oddball paradigm. In the ordered condition, items never repeated; the target was the item that did not follow the order. In the random condition, the observers were instructed which item would be the target while the other items were random and unpredictable. Positive CM in the random condition would indicate task-relevant attention effect. From random to ordered condition, CM increment would imply prediction error effect; from ordered to repeated condition, it would imply repetition suppression. Results in Exp 1 and 2 revealed task-relevant attention and repetition suppression effects (Fig 2a,b); results in Exp 3 showed only task-relevant attention effect (Fig 2c). In Exp 1 and 2, attention and repetition suppression contributed about equally. In all experiments, CM correlations between sequence type condition pairs were mostly significant (Tab 1), indicating a common factor, which is likely task-relevant attention. Hence, both attention and repetition suppression are necessary for explaining the original oddball phenomenon. In the special case of colors, attention alone may be sufficient as an account. Meeting abstract presented at VSS 2017