The two general activation systems of affect: Structural findings, evolutionary considerations, and psychobiological evidence

D. Watson and A. Tellegen (1985) proposed a "consensual" structure of affec t based on J. A. Russell's (1980) circumplex. The authors' review of the li terature indicates that this ? factor model captures robust structural prop erties of self-rated mood. Nevertheless, the evidence also indicates that t he circumplex does not fit the data closely and needs to be refined. Most n otably, the modal's dimensions are not entirely independent: moreover, with the exception of Pleasantness-Unpleasantness, they are not completely bipo lar. More generally, the data suggest a model that falls somewhere between classic simple structure and a true circumplex. The authors then examine tw o of the dimensions imbedded in this structure. which they label Negative A ctivation (NA) and Positive Activation (PA). The authors argue that PA and NA represent the subjective components of broader biobehavioral systems of approach and withdrawal, respectively. The authors conclude by demonstratin g how this framework helps to clarify various affect-related phenomena incl uding circadian rhythms, sleep, and the mood disorders.