When a target object embedded in an array of other objects can be distinguished along a single feature dimension (e.g., colour or shape), it can be detected in parallel. When a target object is defined by a conjunction of stimulus features, search has to be conducted serially, indicating that the visual system is incapable of conducting a parallel search over two stimulus dimensions simultaneously. Earlier research has shown that there are two exceptions to this finding. One dimension can be searched in parallel if the other dimension is stereoscopic depth (Nakayama & Silverman, 1986), or relative motion (McLeod, Driver & Crisp, 1988). We report a third exception: if one dimension involves contrast polarity, another dimension (shape) can be searched in parallel. The neurophysiological implications are discussed.
Deze studie laat zien dat er parallel gezocht kan worden naar conjunctie van vorm en contrast polariteit.