Inhibition of the human eyeblink reflex: an evaluation of the sensitivity of the Wendt-Yerkes method for threshold detection.

In two experiments, human subjects showed a reduced eyewink reflex to an airpuff (S2) if it was preceded by a light flash or a noise burst (S1). The first (N=6) showed that a light inhibited the blink maximally at a 100-msec lag. In the second (N=8), thresholds for noise pips were established with the method of limits. Then the pips were presented in multiples of threshold values as S1 100 msec before S2. Sujbects pressed a button whenever they heard the sound, on S1-S2 pairs, on S1 alone, or on S2 alone trials. Eyeblinks to S2 declined in amplitude and increased in latency as S1 intensity increased. The threshold S1 (approximately 2 dB over a 50-dB background) produced reliable inhibition in 7 of 8 subjects, and a weaker S1 which never evoked a button press was sufficient to produce reliable inhibition for the group as a whole. Inhibition in any particular trial was unrelated to button pressing. The sensitivity of the reflex technique and its relative invariance to task demands suggest its usefulness as a behavioral psychophysical procedure.