Emerson Foulke

The Comprehension of Rapid Speech by the Blind

DOCUMENT RESUME

Expanding the tactual field of view

Can tactual information be acquired simultaneously by several different fingers? Blind and sighted Ss were asked to scan vertical displays of braille (consisting of either one or two dots) with the index and middle fingers on each hand-using one, two, or four fingers at the same time. Stimuli were recognized most rapidly when the displays were scanned by two fingers on different hands and least rapidly when two fingers on the same hand were used; performance was similar with one finger and with four fingers. The results indicated some parallel perceptual processing of the inputs to the two hands and mutual interference in processing inputs from fingers on the same hand.

EFFECTS OF COMPLEXITY AND REDUNDANCY ON THE TACTUAL RECOGNITION OF METRIC FIGURES

An attempt was made to assess the influence of two information parameters, viz., complexity and redundancy, on the tactual recognition of metric figures by 24 sighted and 24 blind Ss. Four levels of complexity were used with random and Redundancy-1 forms. The stimuli were raised dots and standard braille values were employed for dot height and spacing. Efficiency of performance was measured in terms of both speed and accuracy of recognition. Although the results were in part dependent upon response measures, the following overall trends were noted: (a) efficiency of performance was greater in the blind than in the sighted Ss and for random as compared to Redundancy-1 figures and (b) speed and accuracy of recognition tended to decrease with increments in stimulus complexity. The data were interpreted as supporting central factors in form perception and as illustrating the need for close attention to the nature of performance indices employed in the study of the perception of form.

A human factors approach to the assessment of the mobility of blind pedestrians.

Improving the mobility of blind pedestrians will require the application of methods developed by human factors specialists. Mobility must be recognized as a complex skill, the analysis of which will provide the information that is needed for the design of mobility aids, the development of training methods, and the evaluation of both. This paper suggests some of the requirements of a method for assessing the mobility of blind pedestrians. In so far as possible, mobility should be studied in a situation that provides both experimental control and reasonable fidelity to those situations in which the mobility task is ordinarily performed. Measures should be independent of the mobility aid used by the blind pedestrian. They should be operationally defined. They should assess behaviors that lead to the realization of the terminal objective of the mobility task. Finally, measures should be included that permit valid inferences concerning the perceptual and cognitive processes upon which mobility depends, so that a more adequate theory of mobility can be developed.

TRANSFER OF A COMPLEX PERCEPTUAL SKILL.

Communication systems that depend upon stimulation of the skin will be more flexible and useful if it is possible to shift to new sets of loci in accordance with the needs of particular situations. However, the feasibility of making such shifts will depend upon the amount of transfer that can be expected. To explore this problem, an experiment was performed in which braille readers served as Ss. They were required to read lines of braille characters with each of eight fingers. Performance was best when the forefingers were used and fell off sharply as the little fingers were approached. Explanations of the results in terms of anatomical, physiological and experiential factors were discussed. Some implications for cutaneous communication systems in general were suggested.

Comparison of comprehension of two forms of compressed speech.

An experiment was performed to determine the influence of word rate and the method used in compressing speech upon listening comprehension. One group of subjects heard speech made rapid by means of the Tempo Regulator. The other group heard speech made rapid by playing a record at a faster speed than the one used during recording. Each group was further divided into three subgroups, and each subgroup heard the selection at a different accelerated word rate. The three word rates employed were 253, 300, and 350 words per minute. Following this, subjects took a multiple choice test of listening comprehension based upon the selection heard. The analysis of variance of test scores showed the word rate variable to be highly significant. However, the method used in compressing speech was not a significant variable.

SPATIAL ABILITY AND THE LIMITATIONS OF PERCEPTUAL SYSTEMS

Our reason for participating in this symposium is to share what we know and discover what we do not know about the spatial ability of humans, and to become clearer about what we need to know. There are many ways to seek an understanding of spatial ability, and the approach I have chosen is to consider the performance of a task that depends on spatial ability, and the results of efforts to build electronic devices to facilitate the performance of that task. The task I have in mind is the task in which blind pedestrians engage when they travel independently, and the electronic devices are the electronic travel aids (ETAs) that have been designed and evaluated over the past several decades. I will discuss both the task and the ETAs shortly, but first I would like to set the stage by indicating the importance of independent travel to blind pedestrians, and by reviewing briefly the history of efforts to develop techniques and tools which, when properly used by blind pedestrians, will afford at least a measure of independence in travel.

Visual Impairment and the Development of Perceptual Ability

In order to be considered legally blind, a person must have “central visual acuity of 20/200 or less in the better eye, with correcting lenses; or central visual acuity of more than 20/200 if there is a field defect in which the peripheral field has contracted to such an extent that the widest diameter of the visual field represents an angular distance no greater than 20 degrees” (American Foundation for the Blind, 1967). As a consequence of the legal definition, the word “blind” is used as a label that groups together people who are totally without sight and people with a considerable degree of vision. Therefore, it might prove advantageous to use other functional criteria in defining degrees of blindness, such as the ability or inability to read newspaper print, vision that is useful for reading but not for travel, or vision that is useful for travel but not for reading.

Transmission of Morse Code by Electrocutaneous Stimulation

Two Morse code operators who could receive code at the rate of 20 words per minute or faster were given training in the reception of 4 and 5 member groups of Morse code characters, presented by means of electrical stimulation of the skin. Near the end of the training, one S demonstrated the ability to receive 10 five-character groups per minute with an accuracy of 96%. Results are promising enough to justify further exploration.

Reaction time to electrocutaneous onset and offset stimulation.

Reaction times were obtained from two Ss to the onset (beginning) and offset (cessation) of 70 cps AC electrocutaneous stimuli of three sensation levels: low, medium and high. The results indicated that onset was faster than offset RTs at all three intensity levels.