Alpha and Theta EEG in Vigilance

During a 1-hr. vigilance session Ss were required to detect specified digit triads in an uninterrupted random digit series. EEG was recorded continuously with sampled epochs analyzed by computer for autocorrelation and period analysis. Correlogram ratios indicated progressively decreasing arousal through the session but did not distinguish responses from detection failures. Incidence of alpha waves by period analysis also did not identify errors, but incidence of theta waves dropped significantly just prior to failures and did not do so around responses.