It has been argued that an important determinant of the cardiac response is the subject's intended transaction with his or her environment. The present study was designed to investigate whether cardiac deceleration would accompany the solution of a perceptual discrimination problem, and moreover, whether the degree of cardiac deceleration would be related to the accuracy of the response. Fifty-one subjects, 44 months of age, were each given 20 trials of a matching figures task. This task required that S match a figure (called standard) to one of four variations (one of which was identical to the standard). ECG was continuously recorded along with the latency and the accuracy of the response. If the first response was incorrect, S was asked to choose again. The results indicated four major findings. (1)There was a significant cardiac deceleration from the time S received the standard until he or she made his or her first choice. If the first response was correct, the cardiac rate, within 1-3 beats, returned to resting level; however, if S was told to guess again, the cardiac rate remained decelerated. (2)Correct responses were associated with significantly greater cardiac deceleration than incorrect responses; however, both accuracy of response and amount of deceleration were correlated with response time. (3)In general, the degree of cardiac deceleration was significantly correlated with general intellectual function as measured by a standard IQ test. (4)There were important and consistent sex differences in cardiac responsivity. The results of this study suggest that for the very young female child, autonomic responsivity, specifically cardiac deceleration, is directly related to S's efficiency both in terms of her general intellectual functioning and her specific performance--the accuracy of her response.