Further learning effects of knowledge of results upon time estimation

College students of both sexes served as their own controls to test four hypotheses in each of three experiments designed to assess effects of knowledge of results (KR) as verbal information correct to the nearest .01 sec. on time estimations. Analysis indicated that (1) KR significantly increased the mean accuracy of time estimations obtained by the methods of production and estimation but not by the method of reproduction, (2) that KR significantly decreased the variance of the time estimations in all three experiments, (3) that in all three experiments after KR underestimators significantly increased their mean time estimates whereas overestimators significantly decreased their mean time estimations, and (4) that no significant sex differences were present. Notions of excitation and inhibition as intervening variables and of the Pavlovian first- and second-signalling systems were employed in tentative explanations.