Motor and cognitive factors in the modification of a reflex.

Abstract

By closing a hand-held switch, subjects caused a miniature solenoid to deliver a tap to their own foreheads. (1) The amplitude of elicited eyeblinks was reduced when the delay between switch closure and tap was 50 meec or less. (2) Subjects who expected that switch closure would produce an immediate tap exhibited smaller blinks to such taps than did subjects who expected switch closure to produce a delayed tap. (3) The inhibitory effects of a reflex-modifying tone prior to tap were the same when taps were self-presented as when they were presented by the experimenter. (4) When blinks could be elicited by either a tap or a loud noise, the smallest responses occurred when subjects knew which to expect. (5) On a given trial, the inhibition afforded by the particular stimulus, motor, and cognitive factors operating at the time tended to add in an algebraic fashion.