Carl E. Sherrick

Apparent haptic movement

When as were presented with 150-Hz vibrotactile bursts at two loci on the skin of the thigh and permitted to adjust the time between burst onsets, they reported good apparent movement between the loci. The time between stimulus onsets for optimal movement was found to vary directly with the duration of the stimulus. Replication of the experiment with electrocutaneous stimuli at 1 KHz yielded similar results. Comparison of the data with results from a study of visual apparent movement revealed no difference between the two modalities for the relationship between stimulus onset intervals and stimulus duration. The significance of the results for hypotheses about the processes underlying perception of apparent movement is discussed.

Basic and applied research on tactile aids for deaf people: Progress and prospects

A brief introduction describes the alternative methods for replacement of the sense of hearing, including the educational procedures of sign language and lipreading, the medical procedure of cochlear implants, and the sensory substitution procedures of visual or tactual displays. For the tactual displays, which are most commonly electronically activated, a listing of desirable objectives is discussed in some detail. Among these are a better understanding of the processing capabilities of the skin, the form an efficient transducer may take, and what features of the speech stream may most profitably be extracted for processing and display to the sense of touch. Because the technology for device design and production in this area is seriously retarded, a great amount of space is devoted to the precise specification of a transducer for the tactile display; included is a discussion of direct electrocutaneous stimulation as a realistic alternative. A number of multichannel displays exist, and several of these may be workable systems if their transducer elements can be kept small and use little energy. What is of current, even urgent, importance is the early and widespread deployment of a single‐channel tactile aid to permit the general assessment of the effectiveness of a simple sensory adjuvant for a deaf person who has lipreading skills.

The cutaneous saltatory area and its presumed neural basis

The saltatory area, defined as that region of the skin within which two successive and spatinily separated signals will interact to produce apparent mislocalization of the prior signal, is measured by a campimetric technique applied to the palm, finger pad, and volar forearm. As contrasted with earlier measures on larger anatomical units, saltatory areas of the hand region are considerably compressed. Comparisons between cortical receptive fields and saltatory areas lead to speculation concerning the operation of the neural principle of “magnification” in the establishment of saltatory limits. The correspondence of configurational properties of both receptive fields and saltatory areas suggests a commonality of principles underlying both, but demands more information on the temporal dimensions of cortical interaction to confirm the parallelism.

Multiple Cutaneous Stimulation: The Discrimination of Vibratory Patterns

In an effort to supply widespread cutaneous stimulation and thus make possible systematic study of the limits of spatial discrimination through this channel, there has been devised a multiple contactor system permitting application of vibratory signals to 10 bodily loci simultaneously. Patterns comprising from 1 to 9 stimuli were presented in successive pairs, the subjects task being to report whether the patterns were perceived as “same” or “different.” Members of pairs were separated by 500 msec and burst duration was 200 msec. Two synchronized Western Union tape transmitters presented 20 programs of 50 pairs of patterns, 500 “same” and 500 “different” pairs being randomly intermixed in the 1000 presentations. A pilot experiment, in which many types of pattern changes were explored, revealed errors to be associated with (a) relative pattern complexity (large numbers of vibrators) and (b) high degree of communality (many elements in common). A formal experiment, involving a stratified sample with all co...

A scale for rate of tactual vibration

Observers were asked to make estimates of the rate of mechanical vibrations presented to the finger as pulses ranging from 2 to about 300 pps. From the functions generated by this study, a set of ten values of mechanical vibration rate was selected. In a second experiment additional observers were asked to learn to identify these values of rate. Information analysis of the data showed that, when rate alone is varied, observers can identify between three and five items correctly; when rate and intensity are covaried redundantly, between five and eight items can be identified correctly. These results are viewed as supporting those from studies of the DL for rate, and as evidence for a limited but useful role of rate discrimination in tactile displays of acoustic signals.

The role of skin coupling in the determination of vibrotactile spatial summation

A series of three experiments was carried out to determine the effects of variation of static force and contactor area on both absolute thresholds and the magnitude of vibrotactile stimuli at frequencies of 20, 80, and 250 Hz. The findings were: (a) If contactor penetration into the skin is constant, vibratory threshold amplitude falls off at the rate of 3 dB per doubling at 250 Hz, in agreement with previous studies, (b) There is no increase in vibrotactile magnitude with increase in area at constant amplitude, (c) Increasing static force on the contactor produces an increase in the vibrotactile magnitude. Also, changing contactor force can shift the exponent of the vibrotactile magnitude function. Some discussion is given of the questions raised by the present research, in particular the question of whether static conditions modify not only the mechanics of wave propagation, but also the excitability of neural systems in the tissues.

Bilateral apparent haptic movement

When Os are permitted to manipulate the interstimulus onset interval (ISOI) to obtain optimal apparent movement between two ipsilateral vibrotactile stimuli, a consistent quantitative relation between ISOI and stimulus duration appears. The present report describes conditions for movement between contralaterally-placed stimuli, and shows that whereas movement is qualitatively incomplete, the aforementioned relation is still evident. The results are discussed in the light of recent work in both visual apparent movement and complex patterns of stimulation on the skin.

A computer-controlled matrix system for presentation to the skin of complex spatiotemporal patterns

A system for presenting complex spatiotemporal patterns to the skin is described. The computer-controlled device consists of a matrix of 64 piezoceramic benders mounted in a support system that can be fitted to steeply contoured skin surfaces such as the thigh. Vibrotactile patterns that include movement across the skin’s surface and/or intensitive variation within or across display epochs are programmed and presented in a frame-by-frame manner, similar to the production of motion pictures. Patterns can be predefined, or modified by observers’ responses to allow for an interactive haptographic display. Design considerations for the construction of the tactile matrix, computer interface, and software are discussed.

Touch as a communicative sense: Introduction

A brief survey is made of some of the threads of research and theory that have converged upon the problems of application of the touch sense to the task of substituting for the hearing process.

A case study of the tracking skill of a deaf person with long‐term tactile aid experience

The paper describes a case study of Dimitry Kanievski, a deaf individual who has been using a vibrotactile aid for approximately 13 years. He has acquired the ability to lipread speakers in three languages, using the Kanievski speech‐analyzing device. The report describes his communicative abilities with and without the aid in his native language, Russian, as well as in English and Hebrew. When Dr. Kanievski was tested with the De Filippo‐Scott tracking technique, the aid provided for a considerable improvement in performance over unaided lipreading scores. The degree of improvement, however, was a function of several factors, in particular his unaided lipreading rate for the different languages. Plotting the ratio of aided to unaided performance against unaided tracking rate yielded a power function. [Work supported by NIH Grant NS‐04775.]