Affect (psychology)
Affect, like the adjective affective, refers to the experience of feeling or emotion. Affect is a key part of the process of an organisms 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 classical divisions of psychology: the cognitive, the conative, and the affective. One current psychological theory, the lateralization of brain function, holds that one half of the brain deals mainly with the affective or emotional, while the other half deals mainly with the cognitive or rational. In certain views, the conative may be considered as a part of the affective, or the affective as a part of the cognitive..
This article discusses theoretical perspectives, history and psychological meanings of the term, as well as distinctions between mood and emotion.

# Theoretical perspective
The term "affect" can be taken to indicate an instinctual reaction to stimulation occurring before the typical cognitive processes considered necessary for the formation of a more complex emotion. Robert B. Zajonc asserts this reaction to stimuli is primary for human beings, and that it is the dominant reaction for lower organisms. Zajonc suggests affective reactions can occur without extensive perceptual and cognitive encoding, and can be made sooner and with greater confidence than cognitive judgments (Zajonc, 1980).
Many theorists (e.g., Lazarus, 1982) consider affect to be post-cognitive. That is, affect is thought to be elicited only after a certain amount of cognitive processing of information has been accomplished. In this view, an affective reaction, such as liking, disliking, evaluation, or the experience of pleasure or displeasure, is based on a prior cognitive process in which a variety of content discriminations are made and features are identified, examined for their value, and weighted for their contributions (Brewin, 1989).
A divergence from a narrow reinforcement model for emotion allows for other perspectives on how affect influences emotional development. Thus, temperament, cognitive development, socialization patterns, and the idiosyncrasies of one's family or subculture are mutually interactive in non-linear ways. As an example, the temperament of a highly reactive/low self-soothing infant may disproportionately affect the process of emotion regulation in the early months of life (Griffiths, 1997).

# History
A number of experiments have been conducted in the study of social and psychological affective preferences (i.e., what people like or dislike). Specific research has been done on preferences, attitudes, impression formation, and decision making. This research contrasts findings with recognition memory (old-new judgments), allowing researchers to demonstrate reliable distinctions between the two. Affect-based judgments and cognitive processes have been examined with noted differences indicated, and some argue affect and cognition are under the control of separate and partially independent systems that can influence each other in a variety of ways (Zajonc, 1980). Both affect and cognition may constitute independent sources of effects within systems of information processing. Others suggest emotion is a result of an anticipated, experienced, or imagined outcome of an adaptational transaction between organism and environment, therefore cognitive appraisal processes are keys to the development and expression of an emotion (Lazarus, 1982).

# Non-conscious affect and perception
In relation to perception, a type of non-conscious affect may be separate from the cognitive processing of environmental stimuli. A monoheirarchy of  perception, affect and cognition considers the roles of arousal, attentional tendencies, affective primacy (Zajonc, 1980), evolutionary constraints (Shepard, 1984; 1994), and covert perception (Weiskrantz, 1997) within the sensing and processing of preferences and discriminations.     Emotions are complex chains of events triggered by certain stimuli. There is no way to completely describe an emotion by knowing only some of its components. Verbal reports of feelings are often inaccurate because people may not know exactly what they feel, or they may feel several different emotions at the same time. There are also situations that arise in which individuals attempt to hide their feelings, and there are some who believe that public and private events seldom coincide exactly, and that words for feelings are generally more ambiguous than are words for objects or events.
Affective responses, on the other hand, are more basic and may be less problematical in terms of assessment. Brewin has proposed two experiential processes that frame non-cognitive relations between various affective experiences. Those that are prewired dispositions (i.e.. non-conscious processes), able to select from the total stimulus array those stimuli that are casually relevant, using such criteria as perceptual salience, spatiotemporal cues, and predictive value in relation to data stored in memory (Brewin, 1989, p.381), and those that are automatic (i.e.. subconscious processes), characterized as rapid, relatively inflexible and difficult to modify...(requiring) minimal attention to occur and...(capable of being) activated without intention or awareness (1989 p.381).

# Arousal
Arousal is a basic physiological response to the presentation of stimuli. When this occurs, a non-conscious affective process takes the form of two control mechanisms; one mobilization, and the other immobilizing. Within the human brain, the amygdala regulates an instinctual reaction initiating this arousal process, either freezing the individual or accelerating mobilization.
The arousal response is illustrated in studies focused on reward systems that control food-seeking behavior (Balliene, 2005).  Researchers focused on learning processes and modulatory processes that are present while encoding and retrieving goal values.  When an organism seeks food, the anticipation of reward based on environmental events becomes another influence on food seeking that is separate from the reward of food itself.  Therefore, earning the reward and anticipating the reward are separate processes and both create an excitatory influence of reward-related cues.  Both processes are dissociated at the level of the amygdale and are functionally integrated within larger neural systems.

# Affect and mood
Mood, like emotion, is an affective state. However, an emotion tends to have a clear focus (i.e., its cause is self-evident), while mood tends to be more unfocused and diffused. Mood, according to Batson, Shaw, and Oleson (1992), involves tone and intensity and a structured set of beliefs about general expectations of a future experience of pleasure or pain, or of positive or negative affect in the future. Unlike instant reactions that produce affect or emotion, and that change with expectations of future pleasure or pain, moods, being diffused and unfocused, and thus harder to cope with, can last for days, weeks, months, or even years (Schucman, 1975). Moods are hypothetical constructs depicting an individual's emotional state. Researchers typically infer the existence of moods from a variety of behavioral referents (Blechman, 1990).
Positive affect and negative affect represent independent domains of emotion in the general population, and positive affect is strongly linked to social interaction. Positive and negative daily events show independent relationships to subjective well-being, and positive affect is strongly linked to social activity. Recent research suggests that high functional support is related to higher levels of positive affect.    The exact process through which social support is linked to positive affect remains unclear. The process could derive from predictable, regularized social interaction, from leisure activities where the focus is on relaxation and positive mood, or from the enjoyment of shared activities.

# Affect and the present moment
In the book, The Stillness of the Mind, Eckhart focuses on self-awareness and the perception of the present that leads to a cognitive, conscious affective state of the human condition. This present-moment consciousness of affect includes various stimuli processed within the framework of cultures, organizations, and environments, all of which contribute toward the development of the emotional state of the human organism (Tolle, 1999, 2003).

# Social interaction
Affect, emotion, or feeling is displayed to others through facial expressions, hand gestures, posture, voice characteristics, and other physical manifestation. These affect displays vary between and within cultures and are displayed in various forms ranging from the most discrete of facial expressions to the most dramatic and prolific gestures (Batson 1992). Affect display is a critical facet of interpersonal communication. Evolutionary psychologists have advanced the hypothesis that hominids have evolved with sophisticated capability of reading affect displays and detecting deception.

# Meanings in art
The difference between the externally observable affect and the internal mood has been implicitly accepted in art and indeed, within language itself.  The word "giddy," for example, carries within it the connotation that the characterized individual may be displaying a happiness that the speaker/observer believes either insincere or short-living.