Effect of demand characteristics on heart rate during a behavioral avoidance test.

A 2 X 2 experimental design utilized two levels of verbally reported snake fearfulness (high-low) and two levels of experimental demand (high-low) with 16 college student subjects during a behavioral avoidance test. Subjects given high-demand instructions for heart-rate increase increased their heart rate more than subjects given low-demand instructions. Results were specific to heart rate, as demand produced no effects on approach behaviors or fear ratings. Heart rate during the behavioral avoidance test was shown to be as susceptible to experimental demand as other studies have shown approach behaviors to be influenced.