Psychometric, diurnal, and electrophysiological correlates of activation.

Several studies were performed using Thayer's Activation-Deactivation Adjective Check List (AD-ACL). Factor analysis of college students' scores identified a single activation factor representing a continuum ranging from sleep through wakefulness. Next, changes over the diurnal cycle in activation factor scores were demonstrated. One-week test-retest reliability was also investigated. Finally, activation scores were related to pulse rate, respiration rate, and skin resistance level under passive and active conditions. Correlations between factor scores and electrophysiological measures were higher than were intercorrelations of electrophysiological measures, indicating that scores on this revised activation factor represent a valid measure of phenomenological bodily activation level.