Limited attention facilitates coherent motion processing

It has been suggested that sensitivities for visual motion are typically impaired by poor attention. Here, we show that limited attention paradoxically improves performance on a global motion detection task. Psychophysical experiments revealed that deliberately attending to an irrelevant stimulus enhanced sensitivity for detecting coherent motion in random-dot kinematograms but did not affect contrast and velocity sensitivity for local luminance motion. Subsequent experiments further demonstrated that the dual task reduced sensitivity for detecting spatial modulations in local motion direction and induced illusory motion assimilation. Additional measurements confirmed that the secondary task had no effect when attentional load was extremely high or when motion stimuli were presented peripherally. These results may be explained by the idea that limited attention dynamically expands the spatial extent of motion integration by reducing center-surround interactions at high-level motion processing.