John A. Bargh (/ˈbɑːrdʒ/; born 1955) is a social psychologist currently working at Yale University, where he has formed the Automaticity in Cognition, Motivation, and Evaluation (ACME) Laboratory. Bargh's work focuses on automaticity and unconscious processing as a method to better understand social behavior, as well as philosophical topics such as free will. Much of Bargh's work investigates whether behaviors thought to be under volitional control may result from automatic interpretations of and reactions to external stimuli, such as words.

Bargh is particularly famous for his research on priming and its effects on behavior. In one of his most well-known studies, Bargh and colleagues reported that participants who were exposed to words related to the elderly stereotype (e.g., "Florida", "Bingo") subsequently walked more slowly when exiting the laboratory, compared to participants who were exposed to neutral words. This study has been highly influential, with over 5,000 citations. However, attempts to replicate Bargh's studies have failed to find significant effects. So far, there has been a lack of successful preregistered replication studies, and the only support for priming effects come from several large-scale meta-analyses which can not adequately control for the substantial bias in this literature.

Bargh was born in Champaign, Illinois. He attended the University of Illinois as an undergraduate, where he graduated in 1977 with a B.S. in psychology. He then attended the University of Michigan, where he earned an M.A. in 1979 and a Ph.D. in 1981 in social psychology under Robert Zajonc. That same year he was hired as an assistant professor at New York University, where he remained for 22 years. He has since been working at Yale where he has formed the Automaticity in Cognition, Motivation, and Evaluation (ACME) Laboratory.

Bargh was influenced by the work of his Ph.D. advisor at the University of Michigan, Robert Zajonc, who concentrated on the fundamental processes underlying behavior, including an emphasis on affect and cognition. Much of Zajonc's work touched upon processes that occur outside of awareness. Bargh's work in automaticity and unconscious processing further explores the extent to which information processing occurs outside of either intent or awareness. In contrast to Ellen Langer, who denigrated such mental processing as "mindless", Bargh followed the lead of William James in stating that automatized (or "habitualized" in James' terminology) processing can be a beneficial adaptation. Bargh's research focuses on the influence of environmental stimuli on perception and behavior, automatic activation, the effects of conscious and unconscious priming, the psychological effects of physiological stimuli, and implicit cognition. Bargh's concentration on the influence of unconscious and automatic behavior and cognition grows from a fundamental interest in the construct of 'free will.'

Exposure to stimuli in the environment can influence how individuals make impressions of others. Bargh and Pietromonaco randomly assigned subjects to be exposed to words that were either related to hostility or were neutral. The words were presented outside of the subjects' conscious awareness. In a second task, all subjects were asked to read an ambiguous story about a man and rate him on various measures. Those subjects that were subliminally exposed to words related to hostility rated the man more negatively than those subjects in the control condition.

Bargh and Pietromonaco's findings have been further supported by a meta-analysis conducted by Herring et al. (2013), which demonstrated the pervasiveness of automatic evaluation effects across a wide range of stimuli.

Stimuli may be automatically evaluated in ways that affect behavior, an automatic evaluation. In a study conducted by Chen and Bargh, subjects were faster to pull a lever toward themselves (an approach tendency) when a word had a positive valence than a negative valence, and were similarly faster to push the lever away (an avoidance tendency) when the word had a negative valence compared to a positive valence. The "sequential evaluative priming paradigm" refers to the related phenomenon of response times reducing when primed by stimuli with congruent valence. In an examination of the generality of the effects of this paradigm, Bargh, Chaiken, Govender and Pratto show that simply seeing or hearing mention of stimuli triggers automatically activated evaluations. This occurs even when the subject has not been asked to think about their evaluation of the stimulus beforehand. It was further shown that novel stimuli are automatically evaluated and produce the same effect as nonnovel stimuli: when positively valenced novel stimuli prime positively valenced targets, reaction time is faster.

Stimuli presented outside of awareness have also been suggested to influence the interpretation of subsequent ambiguous and semantically unrelated stimuli. Thus subjects asked to define homographs after being subliminally primed with positive, negative, or neutral valence words subsequently evaluated the valence of the ambiguous words with that of the prime.