Abstract
How does affect influence gullibility? After a brief consideration of the nature of gullibility, I describe a series of experiments that explored the prediction that in situations in which close attention to stimulus information is required, negative mood can reduce gullibility and positive mood can increase gullibility. The experiments examined mood effects on truth judgments, vulnerability to misleading information, the tendency to uncritically accept interpersonal messages, the detection of deception, and the tendency to see meaning in random or meaningless information. In all of these domains, positive mood promoted gullibility and negative mood reduced it. The practical and theoretical significance of these convergent findings are discussed, and the practical implications of affectively induced gullibility in real-life domains are considered.
What is the role of affect in gullibility? Does mood influence the way people examine and evaluate doubtful information? Humans are a rather moody species (Forgas & Eich, 2013), and credulity is also a fundamental characteristic of humankind (Greenspan, 2009; Harari, 2014). Public interest in gullibility has increased in recent years, since the emergence of a posttruth world in which the cognitive processes of voters and their openness to simple, populist messages proved surprisingly important in influencing political events, such as Brexit, the ascendancy of Trump, and the election of populist autocrats in once-democratic countries (e.g., Hungary, Turkey; Albright, 2018; Pennycook & Rand, 2019). Social and cognitive psychology have a great deal to contribute to our understanding of gullibility (Gilbert, 1991; Gilovich, 1991), but the role of affect in credulity has not received much prior attention. After a brief discussion of the nature of human gullibility, I will describe a series of experiments demonstrating that positive affect can increase gullibility and negative affect can reduce it in a variety of situations.
What Is Gullibility?
The uniquely human symbolic ability to create, share, and act on secondhand, fictional information or “memes” is one of the most remarkable evolutionary achievements of our species (Dawkins, 1976; Harari, 2014). The propensity to believe, learn from other people, and share information confers significant adaptive benefits (von Hippel, 2018). Yet this symbolic ability can also be the potential source of gullibility, a pejorative term typically defined as a failure of social intelligence in which a person is easily tricked or manipulated to believe unlikely propositions that are unsupported by evidence. Gullibility can be inferred when a person’s beliefs either violate facts and reality or deviate from consensual social norms about reality. Not all gullibility is dysfunctional, and identifying absolute standards of “truth” remains a complex and unresolved philosophical issue (Popper, 1947). For the purposes of the current article, gullibility is proposed as a meaningful and so far little-studied integrative psychological concept that occurs in a variety of situations when people’s beliefs deviate from either objectively available or consensually determined standards of reality.
Throughout history, humans created and have believed many absurd and frequently vicious beliefs, often in a futile attempt to understand, predict, and control their social and physical world (Greenspan, 2009; Harari, 2014; Koestler, 1967). Beliefs in witches, vampires, werewolves, magic cures, magic potions, alchemy, and of course, a flat earth were endemic until quite recently (Pinker, 2018). Yet cautionary stories about gullibility also feature prominently in many folk tales and in classical literature, highlighting the enduring cultural importance of this concept. Trusting the serpent was Adam and Eve’s (and our?) downfall, Homer’s Trojan horse is a classic tale of gullibility, and Othello’s tragedy is also about credulity.
Gullibility Today
In our age, marketing, advertising, and politics continue to exploit the human inclination to believe—gullibility—and often rely on affective manipulations to do so (Forgas & Baumeister, 2019; Gilbert, 1991; Gilovich, 1991). Conspiracy theories, pyramid schemes, alternative therapies, and miracle diets continue to thrive. Some academics are no less gullible. It seems remarkably easy to publish intentionally nonsensical articles in “reputable” academic journals of feminism and grievance studies, as long as those articles demonstrate the expected politically correct tribal bias (Lindsay, Bhoghossian, & Pluckrose, 2018; Sokal & Bricmont, 1998). And many “true believers” in public life continue to promote seductive closed systems of thought, such as nationalism, or Marxism and its manifold derivatives, including various collectivist “social-justice” ideologies that either have been falsified or were constructed to be unfalsifiable in the first place (Forgas & Baumeister, 2019; Popper, 1947). With the advent of the Internet, “truth” and rationality in public life are increasingly at risk, as information is no longer filtered by a trusted class of scientists, experts, and writers (Albright, 2018; Myers, 2019).
There is growing concern about gullibility in politics as well, and affect has long played a role in political credulity (Razran, 1940). Rationality is not a dominant feature of human thinking (Kahneman, 2011). Uncritically accepting information is often the baseline strategy; doubt and rejection may only come later and require additional effort and attention (Gilbert, 1991). Human history is replete with more or less effective and ever-changing belief systems (Harari, 2014). Yet these shared beliefs can also be extremely effective. Our current enlightenment beliefs in liberty and equality serve as the foundation of perhaps the most successful civilization in human history (Pinker, 2018). It is entirely possible, however, that in some future utopia (or dystopia?) our currently deeply held beliefs may also come to be regarded as naive and gullible.
Thus, gullibility appears to be a universal feature of the human condition and an important psychological construct. Understanding the psychological mechanisms that promote or inhibit gullibility is of growing topical interest (Myers, 2019; Pennycook & Rand, 2019). With the rise of populism, demagoguery, “fake news,” political correctness, identity politics, and nationalism, a better understanding of how affective states may influence gullibility is also of considerable practical importance (Pinker, 2018), as I will suggest in the next section.
Affect and Gullibility
Affect has long been suspected as a source of irrationality. Numerous thinkers from Plato to Kant and Freud considered affect to be a primitive and invasive faculty that can overwhelm or subvert rational mental processes (Hilgard, 1980). An early illustration of affective influences on gullibility was provided by Razran (1940), who found that political messages were more effective when recipients were in a positive mood (after a free lunch!) rather than in a bad mood (exposed to noxious smells). More recent work showed, however, that affect can also serve as an adaptive and even essential input to effective social thinking (Damasio, 1994; de Sousa, 1987). In this article, I will focus on how gullibility is influenced by moods (previously defined as low-intensity, diffuse, and relatively enduring affective states) without a salient antecedent cause and therefore little cognitive content (Forgas, 1995).
Moods may influence gullibility primarily by regulating the kind of information-processing strategies people spontaneously adopt (Forgas & Eich, 2013). Specifically, negative moods can trigger a more detailed, attentive, and data-driven processing style, and positive moods produce more creative, theory-driven, and heuristic thinking (Clark & Isen, 1982; Forgas & Eich, 2013; Fredrickson, 2001; Schwarz, Bless, & Bohner, 1991). The processing effects of moods have recently been theoretically integrated in the assimilative-accommodative model proposed by Bless and Fiedler (2006), suggesting that moods perform an important evolutionary signaling function. Accordingly, positive moods signal safe and familiar situations triggering more assimilative, creative, and top-down thinking, whereas negative mood functions as a mild alarm signal recruiting more accommodative, attentive, and externally focused processing. Clinical work on “depressive realism,” although debated, also suggests that negative mood may sometimes produce a more accurate perception of reality (Alloy & Abramson, 1988).
This article focuses on situations that call for data-driven processes in which negative mood—recruiting accommodative, externally focused thinking—may provide a distinct advantage in reducing gullibility compared with positive mood. A growing number of experiments support these predictions, showing that people in a mild negative mood pay closer attention to the quality of persuasive arguments, show improved eyewitness accuracy, pay closer attention to new information, are less subject to judgmental distortions, and communicate more effectively (Forgas & Eich, 2013; Schwarz et al., 1991; Storbeck & Clore, 2005). In turn, assimilative thinking in positive mood promotes creativity, theory-driven thinking, greater use of mental shortcuts, and heuristics and so may provide processing benefits in a different class of situations (Fredrickson, 2001). Extrapolating from past work, I expected here that negative mood should reduce and positive mood increase gullibility whenever close attention to new, external information is required. This prediction was examined in a series of experiments exploring mood effects on (a) the truth bias, (b) nonsense detection, (c) interpersonal gullibility, (d) the detection of deception, and (e) gullibility in eyewitness reports.
Experimental Evidence for Mood Effects on Gullibility
Mood effects on believing doubtful claims
Much of the everyday information we receive from other people may be doubtful and has unknown truth value. People often rely on simple heuristics such as familiarity and ease of processing (fluency) to decide whether to believe or disbelieve a claim with unknown truth value (Unkelbach, 2006). In one experiment, a colleague and I investigated the joint effects of mood and ease of processing on believing a variety of doubtful claims (e.g., “Syntagm is the antonym of paradigm,” “The world’s tallest tree is a spruce”; Koch & Forgas, 2012). After a mood induction (viewing positive or negative films), participants judged the truth of various such doubtful statements presented with either high or low perceptual fluency (high or low visual contrast).
Highly fluent claims (high visual contrast) were judged as significantly truer overall than disfluent claims. Consistent with Bless and Fiedler’s (2006) assimilative-versus-accommodative-processing model, results showed that negative mood eliminated and positive mood maintained people’s reliance on processing fluency as a heuristic cue indicating truth (Fig. 1). Participants in a negative mood were also more attentive to the quality of the claims, a result that is conceptually similar to earlier findings that people in a negative mood also play closer attention to the quality of persuasive arguments, compared with people in a positive mood (Schwarz et al., 1991). Thus, moods can influence people’s tendency to rely on heuristic shortcuts such as fluency in veracity judgments.
Mood effects on truth judgments: the effect of positive, neutral, and negative mood and high or low cognitive fluency on the proportion of ambiguous statements judged as true. Error bars show standard errors. (Data from Koch & Forgas, 2012.)
Nonsense receptivity: perceiving meaning where there is none
Inferring meaning in random or meaningless information is surprisingly common, even among academics (Sokal & Bricmont, 1998). Pennycook, Cheyne, Barr, Koehler, and Fugelsang (2015) confirmed this effect, showing that people—including some academics—often perceive vacuous, pseudoprofound nonsense text as meaningful (Lindsay et al., 2018). In one study, my colleagues and I asked participants in a positive or negative mood (after viewing cheerful or sad videotapes) to rate the meaningfulness of two kinds of verbal nonsense text, including vacuous New Age pronouncements (e.g., “Good health imparts reality to subtle creativity”) and meaningless pseudoscientific psychological jargon phrases (e.g., “subjective instrumental sublimations”; Forgas, Matovic, & Slater, 2018).
As expected, participants in a positive mood saw more “meaning” in these gibberish texts (see Fig. 2). Positive-mood judges were not only more gullible but also took less time to produce a judgment; they also had worse recall and recognition memory than did those in the neutral- and negative-mood conditions, consistent with the predicted processing differences.
Mood effects on nonsense receptivity (seeing meaning in nonsense sentences): the effect of positive, neutral, and negative mood on meaningfulness ratings of nonsensical New Age jargon statements and pseudoscientific jargon terms. Error bars show standard errors. (Data from Forgas, Matovic, & Slater, 2018.)
In a conceptual replication, we used abstract visual rather than verbal stimuli. Participants in public places received a mood induction (reminiscing about positive or negative life episodes) and then judged the meaningfulness of four abstract expressionist images by Jackson Pollock and other artists (Forgas et al., 2018). Positive mood again significantly increased the perceived meaningfulness of these indeterminate, nonfigurative images, compared with negative mood.
Mood effects on interpersonal gullibility
Deception, dissimulation, and manipulation are very common strategies in interpersonal behavior, and detecting deception and misleading messages is of great importance not only in our personal lives but also in forensic, judicial, and investigative practice (Fiedler & Walka, 1993). People are generally poor at detecting interpersonal deception (DePaulo, 1992), and mood may play a particularly important role in such judgments. For example, when rating the genuineness of positive and negative facial expressions displayed by professional actors, participants in a positive mood believed the expressions to be more genuine than did those in the neutral- and negative-mood conditions (Forgas & East, 2008b). This mood effect on accepting nonverbal displays at face value was further confirmed when participants evaluated the sincerity of specific, discrete facial emotions displayed by actors (happiness, anger, sadness, disgust, surprise, and fear). Participants in a positive mood displayed significantly greater credulity than participants in a negative mood across all emotional expressions except surprise (see Fig. 3).
Mood effects on nonverbal gullibility: the effect of positive and negative mood on mean ratings of the truthfulness of six facial expressions. Error bars show standard errors. (Data from Forgas & East, 2008b.)
Detecting ambiguity in verbal messages is an equally important task. In one study (Matovic, Koch, & Forgas, 2014), participants received a video mood induction and were next asked to correctly identify whether or not sentences were ambiguous. Results showed that negative mood resulted in the more accurate detection of linguistic ambiguity than did positive mood, consistent with the adoption of a more accommodative processing style. This role of processing style in producing this effect was confirmed by evidence for more extensive processing latencies and the more accurate recall by participants in a negative mood (Fig. 4).
Mood effects detecting verbal ambiguity: the effect of positive and negative mood on (a) the mean ability to correctly detect ambiguous sentences, (b) the mean time taken to process the task, and (c) the mean percentage of correctly recalled target sentences. Error bars show standard errors. (Data from Matovic, Koch, & Forgas, 2014.)
Detecting intentional deception presents an even more difficult cognitive task for the gullible. In one study (Forgas & East, 2008a), participants viewed mood-inducing films and then watched the interrogation of targets who were either truthful or deceptive in denying an alleged theft. As expected, negative mood not only resulted in more guilty judgments overall but also significantly improved the accurate detection of deception when it occurred.
Mood and eyewitness gullibility
Eyewitness reports are easily contaminated by misleading information received after the event, itself a form of gullibility (Loftus, 1998). In several experiments, we found that negative mood significantly reduced eyewitness gullibility (Forgas, Laham, & Vargas, 2005). For example, students in a lecture hall first witnessed a staged aggressive incident between a lecturer and a female intruder. A week later, when in a manipulated negative or positive mood, eyewitnesses received misleading information (embedded in leading questions) about the witnessed encounter. Positive mood increased and negative mood almost completely eliminated eyewitness gullibility and the incorrect infusion of misleading details into memory, consistent with negative affect promoting more attentive and accommodative thinking (Fig. 5). Conceptually similar results were reported by Storbeck and Clore (2005), who also found that “individuals in negative moods were significantly less likely to show false memory effects than those in positive moods” (p. 785).
Mood effects on eyewitness gullibility: the effect of happy, neutral, and sad mood on false-memory judgments after participants were and were not given leading questions. Positive mood increased and negative mood decreased (compared with neutral mood) the incorporation of misleading information (false recall) into eyewitness memory: average number of false details incorrectly remembered. Error bars show standard errors. (Data from Forgas, Laham, & Vargas, 2005.)
A signal detection analysis confirmed that negative mood actually improved eyewitnesses’ ability to discriminate between correct and misleading memory details. Eyewitnesses in this situation had no subjective awareness of their mood-induced biases, and even explicit instructions were ineffective at controlling these mood effects (Forgas et al., 2005). These studies offer convergent evidence that moods can have a marked influence on eyewitness gullibility by automatically promoting a more or less focused accommodative processing style.
Discussion
Deciding what to believe and whom to trust are among the most difficult and cognitively demanding tasks we face in everyday life. The universal human propensity to accept and believe symbolic information we receive from other people is essential for social integration and cultural evolution but can also be the source of gullibility and irrational beliefs (Gilbert, 1991; Gilovich, 1991; Harari, 2014). The results reported here offer convergent evidence that mood can influence gullibility in a variety of situations. In tasks in which data-focused thinking was required, negative compared with positive mood resulted in reduced truth bias, nonsense receptivity, and eyewitness gullibility and improved the ability to detect deception. These findings are consistent with our theoretical expectation that positive and negative moods trigger qualitatively different information-processing strategies (Bless & Fiedler, 2006) and have some promising theoretical and practical implications.
Theoretical implications
These studies extend previous work on mood effects on social cognition (Forgas, 2013; Forgas & Eich, 2013) to the new domain of gullibility. Veracity judgments require highly constructive processing that tends to promote mood effects (Fiedler, 2001; Forgas, 1995).When close attention to the external world is required, negative mood (compared with positive mood) can reduce gullibility, consistent with recent affect-cognition theories suggesting that negative affect functions like a mild evolutionary warning signal, promoting more accommodative and attentive processing that increases sensitivity to false or misleading information (Bless & Fiedler, 2006).
These results also extend the recent literature documenting the beneficial effects of negative mood in certain situations, including reducing judgmental errors and improving strategic communications (Forgas, 2013; Forgas & Eich, 2013). These effects are often mediated by subtle contextual cues, and affective influences on gullibility may also depend on pragmatic and situational variables such as the motivations, personality, and affective intelligence of the individual (Fiedler, 2001; Forgas, 1995; Forgas & Eich, 2013). Of course, negative mood is not always beneficial, and in many situations, more assimilative, creative, and theory-driven thinking produced by positive mood has functional advantages (Fredrickson, 2001).
Practical implications
Given the strong human propensity to believe rather than disbelieve (Gilbert, 1991; Gilovich, 1991), reducing everyday gullibility is of considerable applied importance. Professionals in the persuasion business, such as advertisers, salesmen, and politicians, have long suspected that positive mood is likely to reduce scrutiny and promote credulity (Razran, 1940). These experiments provide empirical support for this assumption and also offer some evidence for the psychological processing mechanism responsible for this “happy-and-gullible” versus “sad-and-skeptical” effect. Future research may explore mood effects on gullibility in more complex and realistic interactive situations and also investigate the consequences of specific emotions, such as fear, disgust, and anger, for gullibility and skepticism. Understanding these mechanisms has some important practical implications for improving affective intelligence in everyday life and could also be incorporated in the training of counsellors and applied-persuasion professionals.
These results also help to highlight the often-neglected adaptive benefits of negative affect and help to counterbalance the one-sided hedonistic emphasis on the benefits of happiness in popular culture. Negative affect can not only reduce gullibility but also decrease judgmental mistakes, improve memory, and facilitate effective communication (Forgas, 2013; Forgas & Eich, 2013; Storbeck & Clore, 2005). These findings confirm that both positive and negative affective states can play an important adaptive role in how we respond to everyday challenges. Accordingly, temporary negative affect should be accepted as a normal and adaptive feature of everyday human functioning.
In summary, judging the veracity of social information can be a demanding cognitive task that requires highly constructive processing strategies. These experiments extend recent research on affect and social cognition to the new domain of gullibility and skepticism and suggest that further work on affective influences on veracity judgments, gullibility, and skepticism should be of considerable theoretical as well as applied interest.
Recommended Reading
Forgas, J. P., & Baumeister, R. (2019). (See References). A good survey of the latest social psychological research on gullibility and its causes, including conspiracy theories.
Forgas, J. P., & Eich, E. (2013). (See References). A good overall review of the literature on affective influences on social cognition and judgments.
Gilovich, T. (1991). (See References). An exploration of the cognitive, social, and motivational processes through which even highly educated people become convinced of the validity of questionable beliefs and the psychological processes that contribute to faulty reasoning and decisions.
Greenspan, S. (2009). (See References). An excellent and readable review of the problem of gullibility in the areas of religion, politics, science, and medicine, including a historical overview of human gullibility.
Footnotes
Acknowledgements
For further information on my research program, see http://forgas.socialpsychology.org and 
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Action Editor
Randall W. Engle served as action editor for this article.
Declaration of Conflicting Interests
The author(s) declared that there were no conflicts of interest with respect to the authorship or the publication of this article.
Funding
Support from the Australian Research Council for this project is gratefully acknowledged.