Decelerative changes in heart rate are associated with performance on tasks that assess intelligence

Abstract

Changes in heart rate, chin electromyographic (EMG) activity, and respiration rate were monitored during the performance of three tasks that are commonly employed to assess intelligence in human adults. Stimuli from the digit span subtest (Expt. 1) of the Wechsler scales of intelligence, the picture completion subtest (Expt. 2), and the picture arrangement subtest (Expt. 3) were employed. A 10-s warning preceding the onset of each stimulus was also used in each of the experiments. During all three tasks there was an initial increase in heart rate during the first 3–4 s of the warning signal, followed by a decrease in heart rate during the last 5–6 s of the warning signal. Mean heart rate during the 5 s immediately preceding the presentation of stimuli to which subjects gave correct responses was significantly lower than mean heart rate during the 5 s immediately preceding the presentation of stimuli to which subjects gave incorrect responses. In addition, mean heart rate during the 5 s immediately preceding the presentation of stimuli to which subjects gave correct responses decreased significantly below the pre-warning baseline level, whereas mean heart rate during the 5 s preceding the presentation of stimuli to which subjects gave incorrect responses did not decrease below the baseline level. The differential heart rate results for correct and incorrect responses were consistent across the three tasks. No significant changes in chin EMG and respiration rate were noted during any of the tasks. Relationships among heart rate, attention to environmental information, and the role of attention in measures of intelligence are discussed.