Reliability of psychophysiological responding as a function of trait anxiety.

This study examined the temporal stability of three psychophysiological responses (frontal electromyographic activity, hand surface temperature, and heart rate) recorded over four sessions (days 1, 2, 8, and 28) on 34 subjects, 17 with high Spielberger Trait Anxiety Inventory scores and 17 with low scores. Each session consisted of a 20-minute adaptation period, a baseline condition, and two stressors (one cognitive, the other physical). Two forms of reliability coefficients were employed, intraclass correlations and Pearson Product Moment; the two types of reliability coefficients arrived at the same conclusions. Results indicated that reliability coefficients for the two anxiety groups did not differ on frontal EMG or heart rate responses; however, hand surface temperature responding was considerably less reliable for high anxious individuals than low anxious individuals. Reliability coefficients on absolute scores were, for the most part, reliable. Treating the responses as relative measures (percent change from baseline or simple change scores from baseline) produced smaller and less reliable coefficients. Magnitudes of the three physiological responses did not significantly differ as a function of high or low trait anxiety. Findings are discussed in terms of their clinical, as well as basic psychophysiological, importance.