ABSTRACTEvidence is provided showing that there is very little change in pulse volume in the ear lobe as a function of the usual types of psychological stimuli. On the one hand, this makes ear lobe plethysmography an excellent source of a signal to trigger a cardiotachometer for investigators interested in pulse rate who do not want to, or cannot, use EKG recording. On the other hand, this makes the ear lobe an inappropriate place from which to record vasomotor reactivity.