Affect is the experience of feeling or emotion. Affect is a key part of the process of an organism's interaction with stimuli. The word also refers sometimes to affect display, which is "a facial, vocal, or gestural behavior that serves as an indicator of affect" (APA 2006).
The affective domain represents one of the three divisions described in modern psychology: the cognitive, the conative, and the affective. Classically, these divisions have also been referred to as the "ABC of psychology", in that case using the terms "affect", "behavior", and "cognition". In certain views, the cognitive may be considered as a part of the affective, or the affective as a part of the cognitive.
Affective states are psycho-physiological constructs. According to most current views, they vary along three principal dimensions: valence, arousal, and motivational intensity. Valence is the subjective positive-to-negative evaluation of an experienced state. Emotional valence refers to the emotion’s consequences, emotion-eliciting circumstances, or subjective feelings or attitudes. Arousal is objectively measurable as activation of the sympathetic nervous system, but can also be assessed subjectively via self-report. Arousal is a construct that is closely related to motivational intensity but they differ in that motivation necessarily implies action while arousal does not. Motivational intensity refers to the impulsion to act. It is the strength of an urge to move toward or away from a stimulus. Simply moving is not considered approach motivation without a motivational urge present.
All three of these categories can be related to cognition when considering the construct of cognitive scope. Initially, it was thought that positive affects broadened cognitive scope whereas negative affects narrowed cognitive scope. However, evidence now suggests that affects high in motivational intensity narrow cognitive scope whereas affects low in motivational intensity broaden cognitive scope. The cognitive scope has indeed proven to be a valuable construct in cognitive psychology.