Abstract
The oddball paradigm is perhaps the most popular means of studying the neural and perceptual consequences of implicit predictions in the human brain – including implicit visual predictions. The traditional paradigm involves presenting a sequence of identical repeated events, that are eventually broken by a novel ‘oddball’ presentation. Oddball presentations have been linked to increased neural responding, and to an exaggeration of perceived duration relative to repeated events. As the number of repeated events in such protocols is circumscribed, as more repeated events are encountered the conditional probability of a further repeated event diminishes, whereas the conditional probability of an oddball presentation increases. However, these facts have not always been appreciated in analyses of visual oddball protocols. Rather, repeats and oddballs have been treated as binary categories of event. This risks an under appreciation of the impact of event probabilities on measures of neural response and perception. Here we show that event probabilities tend to scale inversely with measures of neural response, and positively with measures of perceived duration – resulting in a negative correlation between measures of perceived duration and neural responding. This relationship is opposite to a popular account of how perceived duration might be linked to neural responding, but it is consistent with the suggestion that perceived durations might scale with the degree of anticipatory attention allocated to an event.