The impact of visual exploration on judgments of whether a gap is crossable

When observers look down into a gap in the ground plane, their judgments of the widest gap they can step across (gap(max)) decrease as gap depth incre ases (Y. Jiang & L. S. Mark, 1994). This study investigated the possibility that Jiang and Mark's viewing conditions did not afford observers a suffic ient opportunity to perform exploratory movements needed to detect informat ion about gap width. Experiment 1 showed that the gap depth by gaze interac tion disappeared only when restrictions were not imposed on observers' expl oratory activities (eye, head, and body movements). Experiment 2 showed tha t observers tended to see the vertical surface as slanted away from them, w hich made the bottom of the surface appear farther away from them than the top. Only when observers were able to view the gap binocularly under condit ions that did not restrict exploratory activity did their slant perception improve and their gap,, judgments no longer covary with gap depth. The data indicate that the exploratory movements of prospective actors are essentia l for the pickup of information about their action capabilities.