Temporal stability of psychophysiological response profiles: Analysis of individual response stereotypy and stimulus response specificity

Temporal stability of frontal electromyographic activity, hand surface temperature,and pulse were recorded from 64 subjects during four sessions over a month's interval. Each session consisted of an adaptation period, a baseline condition, and two stressors (one cognitive, the other physical). Reliability coefficients on absolute scores across sessions were, for the most part, modest and statistically significant. Treating the responses as relative measures (percentage of change from baseline or simple change scores from baseline) produced smaller and less frequently significant correlation coefficients. The data were also examined in a multidimensional manner by using z-scores to determine if each subject showed any consistencies across sessions with respect to which response system was maximally aroused. This analysis led to identifying three groups of subjects: those who responded primarily within a single system across sessions regardless of stressor (individual response stereotypy, 42%), those who responded differentially across sessions to the two stressors (stimulus-response specificity, 20%), and those with profiles not readily classifiable (38%). Subjective ratings by clinicians showed little agreement with these classifications and poor reliability among raters was also obtained. The results are discussed in terms of their clinical implications.