Abstract
Change detection requires comparing the representation of a previously presented stimulus to the representation of a new stimulus. During the interval over which information about the previously presented stimulus is stored, processing of additional information may corrupt the stored representation. The effects of this interference on change detection performance has been shown to depend on allocating attention to the additional information, but is largely independent of the type (visual vs. auditory) of information to which attention is allocated (Makovski, Shim, & Jiang, 2006). In the current experiments, subjects detect changes between the shapes of two smooth, closed, 2D contours presented sequentially, while sometimes also performing a shape-part-counting task between presentations of the change detection displays. On one-third of the trials, the part-counting task was done on a shape similar in structure to the shapes in the change-detection task. On another one-third of the trials, the part-counting task was done on a shape with very different structure - a shape composed of a set of straight lines all meeting at a single point. On the remaining trials, the part-counting task was omitted. Interference due to the part-counting task was measured as the decrease in change detection performance on trials with the part-counting task relative to trials without the part-counting task. Interference effects were dependent on the similarity of the shapes used in the two tasks; similar shapes interfere more than dissimilar shapes. The difference in interference may be reduced or eliminated if the subjects know ahead of time whether there will be an additional, interfering task, and if there is, what type of stimuli will be presented.