Interactions between cognitive space and motor activity
pp. 107-117
in: Fred Mast, Lutz Jancke (eds), Spatial processing in navigation, imagery and perception, Berlin, Springer, 2007Abstract
Extensive signal processing occurs in sensory systems before perception of object positions. Normally this processing is cognitively opaque, inaccessible to experience or behavioral experiment. Several experimental techniques, however, allow analysis of relationships between unconscious processing and subsequent conscious perception and action. In the induced Roelofs effect, a visual target's perceived position is biased by a large static frame that is offset from the center, an effect that appears in perceptual judgment but not in immediate motor activity. Delayed judgment and delayed pointing both show the effect. All four of these results are due to the frame capturing the straight-ahead, a bias that disappears after stimulus offset. The subject, however, is unaware of the bias, believing the straight-ahead (which affects orientation judgments) to remain accurate. Thus an unconscious bias changes conscious behavior. In a further experiment, inattentional blindness prevents perception of the frame. Nonetheless, the induced Roelofs effect appears. This phenomenon requires two dissociable and sequential unconscious steps, processing the frame and biasing the straight-ahead, before conscious responses are altered.