Abstract
Grouping mechanisms are exceedingly important to organize our environment into coherent units. However, perceptual grouping is no unitary process but a mixture of several coexisting mechanisms (e.g. groupings by color, size, connectedness…) which seem to vary fundamentally in their time course and attentional demands. We performed several experiments to compare the influences of different grouping mechanisms on response priming effects. Primes and targets were arranged in a flanker paradigm, such that two primes were presented side by side at the center of the screen. Targets appeared after a stimulus-onset asynchrony (SOA) of either 12, 24, 36, 60, 84 or 108 ms and flanked the primes. In each experiment, two contrasting grouping principles organized the stimuli in vertical or horizontal direction. Primes and targets on each side could be either consistent or inconsistent in their orientation. Subjects should always respond as fast as possible towards the vertically oriented target. Response times showed strong priming effects depending on SOA and task-relevant grouping principles. This also held true for stimuli which could be organized according to two groupings at once so that subject's responses only depended on the particular instruction which to attend. Accordingly, principles of perceptual grouping are in fact considerably different regarding their time course and influences on the visuomotor system. Results are discussed and embedded in current theoretical frameworks.
DFG German Research Foundation.