A demonstration of selection of analyzers for integral dimensions.

Three experiments investigated the integrality of height and width of rectangles and the ability of observers to selectively attend to only one dimension. In Experiment 1, redundancy gain and orthogonal interference were demonstrated in a same/different task. Orthogonal interference was due to the output of the "irrelevant" analyzer interfering with the output of the "relevant" analyzer. These results indicated that height and width are integral, but they can be most parsimoniously explained by assuming that rectangles are initially processed by separate dimensional analyzers. Experiment I demonstrated that with sufficient practice (160 trials), observers are able to selectively attend to the more frequently relevant dimension. Performance for the stressed dimension increased, whereas performance for the unstressed dimension declined. Experiment 3 also demonstrated that with sufficient practice (192 trials), observers are able to selectively attend to the relevant dimension and ignore the irrelevant dimension. Orthogonal interference disappeared. The results are discussed in terms of the ability of observers to modify the perceptual process.