Auditory event-related potentials while ignoring tone stimuli: Attentional differences reflected in stimulus intensity and latency responses in low and highly hypnotizable persons

Effect of hypnotic susceptibility level on auditory event-related potentials (AERPs) was studied as subjects were instructed to ignore tones while reading a novel or counting one's pulse. Assessed previously on two hypnotic susceptibility scales [Harvard Group Scale of Hypnotic Susceptibility; Stanford Hypnotic Susceptibility Scale, Form C (SHSSC)], subjects were 12 low (lows; SHSSC 0-2) and 12 highly (highs; SHSSC 9-12) hypnotizable, right-handed college students. AERPs were recorded at C3, C4, and Cz to 50 ms 1,961 tone pips 50, 60, 70 and 80 dB intensities, pseudorandomly presented at 1.5 intervals. As predicted, highs had significantly smaller N1 and P2 amplitudes than did lows when ignoring tones. As stimuli intensities increased, N1 latencies decreased for lows while N1 latencies increased for highs. N1 latency slopes across the 50 to 80 dB intensities were significantly more negative for lows than highs; slopes correlated significantly with both hypnotizability and absorption (Tellegen Absorption Scale). Thus, the highs appeared to divert greater attentional processing to the tasks at hand, particularly as the tones increased in intensity, and were slower to respond to not-to-be-attended stimuli. These results are interpreted as further evidence for hypnotic susceptibility being associated with efficient attentional processing such that highs can more effectively partition attention towards relevant stimuli and away from irrelevant stimuli than can low hypnotizables.