The oddball effect is the perceived temporal dilation of a deviant stimulus in a train of homogeneous stimuli. A number of models have proposed attentional explanations of the oddball effect, according to which temporal dilation occurs because of the violation of perceptual expectations in a manner akin to repetition suppression effects. On the other hand, the perceived duration of a stimulus is known to depend on its spatial magnitude, such that smaller stimuli are perceived to be shorter in duration. In order to examine these competing effects, we examined the role of the spatial magnitude of oddball stimuli in an oddball duration discrimination task. Participants were presented with a single blue square (oddball) at a random temporal position within a sequence of white squares (standards) of equivalent duration. Oddballs were smaller, equivalent, or larger in physical size and varied in duration. Participants judged whether the oddball was shorter or longer in duration than the standard stimuli. Individual participants’ data were fitted with a logistic function using maximum likelihood estimation and the point of subjective equality, corresponding to the oddball duration perceived to be equivalent to the standard duration, was estimated. The perceived duration of oddballs varied as a function of spatial magnitude: relative to the standard stimuli, larger oddballs were perceived to be longer in duration whereas small and equivalent oddballs were perceived to be shorter in duration. These results are inconsistent with attentional models of the oddball effect and warrant revisions of these models.

time perception; spatial magnitude; attention