The Use of Heart Rate as an Index of Stress in Blind Pedestrians

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Abstract
This paper describes three experiments. The first experiment was designed to investigate the reason for the high heart rate of blind pedestrians when they travelled unaided over a route of medium difficulty. This experiment showed that if the blind subjects were guided over a route by a sighted person, the heart rate of the blind subjects was not significantly different from that of matched sighted control subjects. It was concluded that some form of psychological stress was responsible for the high heart rate of the blind pedestrians when they walked unaided and the use of the guided heart rate as a control measure, specific to each individual, is discussed. In the next two experiments, the results are given in terms of the percentage differences between the heart rate on unguided and guided trials and this measure has been termed the Stress Pulse Ratio (S.P.R.). The second experiment was designed to investigate the effect on heart rate of (a) the aid used by the blind pedestrian (the long cane in this experiment) and (6) familiarity of the subject with the route. No significant difference was found in the S.P.R. of the subjects on the familiar and unfamiliar routes and there was no decrease in the absolute heart rates or the S.P.R.'s over the five sessions as the subjects became more familiar with tho route. This was in marked contrast to the results of Wycherly and Nicklin who employed subjects using either short canes or guide-dogs. They found the heart rate of those subjects decreased over the five sessions. The implications of this difference, in relation to the different aids used by the subjects, are discussed. The third experiment was designed to investigate the effect of route difficulty on the S.P.R. of blind pedestrians. It was found that, even on a traffic and pedestrian-free route, the absolute heart rate levels of the subjects was significantly greater on the unguided trials than on the guided trials. The S.P.R. of the subjects was significantly higher on a more difficult route than it was on the very simple route. A final conclusion is given which discusses the consistencies found throughout the three experiments, and an overall evaluation of the data is attempted.