EFFECTS OF ATTENTION MANIPULATION ON JUDGMENTS OF DURATION AND OF INTENSITY IN THE VISUAL MODALITY

The ''attentional model'' of time estimation assumes that temporal jud gments depend on the amount of attention allocated to the temporal pro cessor (the timer). One of the main predictions of this model is that an interval will be judged shorter when attention is not allocated to the temporal parameters of the task. Previous studies combining tempor al and nontemporal tasks (dual-task method) have suggested that the ti me spent processing the target duration might be a key factor: The les s time devoted by the subject to the temporal task, the shorter the ju dged duration. In the two experiments presented here, subjects were as ked to judge both the duration of a visual stimulus and an increment i n intensity occurring at any time during this stimulus. In the second experiment, trials without intensity increments were added. The main r esult is that the judged duration was shorter when the increment occur red later in the stimulus or did not occur. In those cases, subjects h ad been expecting increment occurrence during most part of the stimulu s and thus had focused for a shorter time on stimulus duration. We pro pose that attention shifts related to expectancy and to detection of t he increment reduce subjective duration.