The effects of hypoxia on choice reaction time and movement time.

Abstract

An investigation was made of the effects on choice reaction time and movement time of hypoxia (oxygen deprivation) induced by a reduction in total air pressure inside a decompression chamber. The subjects were adult humans who were given no pre training on the task used, were tested once at a pressure level equivalent to some altitude between ground level and 15,000 ft, and were given no information on the altitude attained. A variety of tasks were used with simple and complex spatial and code relationships between stimulus and response. In three experiments on 92 subjects in all the most consistent finding was that from gTOund level to 7,000 ft or 10,000 ft there was a significant increase in reaction time and a significant decrease in movement time. Above 10,000 ft the results were less consistent, reaction time showing further increase or a decrease to that found at ground level and movement times varying in the opposite direction to these changes. It was suggested that in young adult subjects and in tasks of low ‘ mental load ’ the inverse variation of reaction time and movement time was quite consistent and was possibly a result of an unimpaired total response time plus a selective impairment of the time taken to initiate a response found only at intermediate altitudes. In tasks with mora ’ mental work ’ involved, hypoxic impairment of total response time was found at altitudes as low as 5,000 ft. Above 10,000 ft there was little further impairment, possibly as a result of some compensatory adjustment in drive or arousal level which might also have been the reason for the lack of impairment of reaction time at the highest altitudes in the simple tasks. The great discrepancy between these results and previous literature, and the additional finding of quicker response times with prolonged exposure to the experimental conditions, were attributed to the separate analysis of reaction time and movement time and the use of naive subjects in a novel experimental design,