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Performance measures on a binary discrimination task and oral temperature readings, were obtained at two times of day, morning (0800) and evening (2000), from each of 18 subjects. On the task, subjects reported not only the presence of signal A or B, but also the confidence of their judgment. A signal detection theory approach was applied to derive separate measures of perceptual efficiency and of the decision-making aspects. The results indicate that whereas efficiency, indexed by d', did not alter significantly between testing times, both response-bias and report confidence did change significantly, the latter showing an increase between morning and evening. A parallel rise in oral temperature was also found, and significant correlations between temperature and confidence were obtained. Neither efficiency nor response-bias was significantly related to temperature. The results are discussed in relation to previous reports that perceptual efficiency and body temperature are related and change in parallel during the normal waking day.
Angus Craig (Thu,) studied this question.