VIBROTACTILE PATTERN PERCEPTION: SOME FINDINGS AND APPLICATIONS
Carl Sherrick Princeton University
When psychologists speak of "the stimulus," the impression all too often gained by their audiences is of a kind of punctate experience in space and time, more or less in keeping with the original Latin definition of the word, which was "a goad." In fact, metaphorical extension of the term lets it comprise a great range of physical events of varying extent, duration, and complexity. In speaking of the tactile stimulus, therefore, we may be describing something as simple as a transient skin displacement, such as a puff of air on the cheek, or as complex as the traveling waves of displacement generated over the entire body when one sits in the chapel listening to a musical passage at full organ from a 32-foot bombard! For this reason it may be better to subsume such events under the general term "stimulus pattern," a phrase that connotes a more or less extended, durative display to the perceptual system, and more realistically represents the psychophysical catenary of events that precede the subject's report.
Definition of Vibrotactile Patterns. Patterns of vibration are not limited to those conditions involving the appearance of long-lasting, periodically varying displacements of the tissues; any transient or sustained disturbance can be analyzed as a distribution of energies over the entire spectrum of vibration frequencies ( Bracewell, 1978; Loomis & Lederman, 1986). The patterns of displacement of the skin produced by braille characters, or by active palpation of two- or three-dimensional objects during attempts at haptic recog