CONTACT AND POSTURE IN NONVISUAL JUDGMENT OF GAP CROSSABILITY

The roles of contact and postural components of haptic probing were in vestigated in 4 experiments. Judgments of the crossability of gaps by blindfolded participants were unimpaired by preventing contact with th e far side of the gap and they were not impaired when participants wie lded only a flashlight that triggered arbitrary sounds when the light struck either side of the gap. Performance was impaired when perceiver s could reach surfaces at varying distances with identical arm movemen ts and, in the 4th experiment, when weights were added to a crossbar o f the probe, perceived crossable gap sizes changed in accord with the prediction that the manipulation would alter the perceived posture. Th ese results support a model of nonvisual gap crossing in which differe nt perceptual modalities can provide information that contact has been made but postural information is necessary for perception of the loca tion of that contact.