Reliability of psychophysiological assessment within temperament-groups.

Four groups of 16 people selected for their relatively extreme scores (greater or equal to 1 S.D. from the mean) on both the E and N scales of the Eysenck Personality Inventory visited the laboratory for four separate but identical testing sessions. Three physiological indices were recorded at each session: heart rate (HR), basal skin conductance level (SCL), and the number of spontaneous skin conductance responses (SCR). Test-retest correlation coefficients were calculated within E x N groups across days. HR and SCR showed moderate to good reliabilities across all groups. The most interesting finding was that SCL was a consistently reliable index for extraverts but not for introverts. Correlations between days were statistically significant for extraverts but not for introverts. A speculative explanation for these results is that SCL is affected by cognitive activity rather than autonomic arousal per se. This study suggests that there are systematic effects of temperament on physiological measures that are important and should not be relegated to error variance.