Disgust facilitates outgroup dehumanization

Disgust: The Exclusionary Emotion

Disgust is widely regarded as a basic, innate emotion geared toward behavioral avoidance, exclusion, and rejection (Rozin, Haidt, & McCauley, 2008). Many aspects of disgust make it relevant to dehumanization, the most critical of which may be its close link to the distinction between humans and animals. As noted by Rozin et al. (2008), disgust elicitors are often animal-related. Animals associated with garbage, death, and disease (e.g., rodents and insects) and the “animalistic” human drives (e.g., sex, aggression, hunger, and waste elimination) are the stimuli most capable of eliciting disgust (Rozin et al., 2008). Once activated, feelings of disgust reliably evoke feelings of superiority over offending targets, who by virtue of their disgustingness, are expelled from the circle of moral regard (Pizarro, Detweiler-Bedell, & Bloom, 2006). As such, disgust guards the human–animal boundary in social cognition, playing the dual role of distancing ourselves from “lower” creatures and reaffirming our own humanity. When applied to intergroup contexts, disgust inserts a psychological boundary between us and them that humanizes us at the expense of the other.

A basic role for disgust in outgroup boundary perceptions is supported by research suggesting that foreign outgroups (Navarette & Fessler, 2006), and groups stereotyped as being low in both competence and warmth (Fiske, Cuddy, Glick, & Xu, 2002) are especially likely to elicit disgust. These competence and warmth dimensions resemble the trait dimensions that convey information about target “humanness” (Haslam, Bain, Douge, Lee, & Bastian, 2005). Disgust also plays a critical role in creating and exacerbating certain types of prejudice (Dasgupta, DeSteno, Williams, & Hunsinger, 2009; Terrizzi, Shook, & Ventis, 2010) and guiding moral evaluations of others (Schnall, Haidt, Clore, & Jordan, 2008). Finally, disgust short-circuits feelings of interpersonal closeness (Sternberg, 2003), providing the ideal conditions for moral disengagement. Disgust, the rejection emotion, may be uniquely equipped to enable dehumanized social cognition.

Previous Research on Dehumanization

Much of the dehumanization (or infrahumanization) research has focused on the preferential attribution of humanizing characteristics, such as complex emotions (e.g., Leyens et al., 2000) or traits such as warmth and intelligence (e.g., Haslam et al., 2005), to ingroups relative to outgroups. Other research has examined implicit associations between outgroups and animals (e.g., Capozza, Boccato, Andrighetto, & Falvo, 2009; Goff, Eberhardt, Williams, & Jackson, 2008; Saminaden, Loughnan, & Haslam, 2010; Vaes, Paladino, & Puvia, 2011; Viki et al., 2006). Although these studies document a widespread dehumanizing bias in judgments of social and ethnic outgroups, it is not clear whether outgroup status per se (e.g., Tajfel, Billig, Bundy, & Flament, 1971) is sufficient for activating animalistic forms of dehumanization (but see Demoulin et al., 2009; Kofta, Baran, & Tarnowska, in press; Mirosławska & Kofta, 2007, for minimal-groups findings using emotion-focused infrahumanization measures).

With respect to the role of disgust in dehumanization, there is evidence that feelings of disgust may weaken or block perceptions of target humanity. In two social-neuroscience investigations, Harris and Fiske (2006, 2007) found that members of certain disgust-eliciting outgroups fail to be processed as fully human, social entities. Correlates of dispositional disgust sensitivity resemble these findings. Hodson and Costello (2007) reported positive correlations between interpersonal disgust sensitivity and a tendency to dehumanize immigrants with respect to “uniquely human” personality traits.

The above findings empirically document an association between disgust and dehumanization, however, the causal status of disgust in outgroup dehumanization has not been investigated experimentally. There is also no confirmation that directly animalistic dehumanization processes occur in the absence of prior attitudes, making the minimal conditions necessary for dehumanization unclear. The current research sought to address that gap in the literature by examining whether disgust can cause people to associate an arbitrary outgroup with animals.

Overview of the Current Study

This study examined the effect of disgust on implicit associations between outgroups and animals, as measured with a modified version of the Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998) and using a minimal-groups paradigm (e.g., Tajfel et al., 1971). To test the disgust-dehumanization hypothesis, we primed feelings of disgust, sad, or neutral emotions. We predicted that incidental feelings of disgust would produce implicit dehumanizing biases, such that participants in the disgust condition would associate outgroup members with animality and ingroup members with humanity. In contrast, sad and neutral emotions were not expected to produce or augment dehumanizing biases.

Method

Results

Dehumanization IAT Analyses

Descriptive statistics for the dehumanization IAT are presented in Table 1. Ninety-five percent confidence intervals (95% CIs) for the IAT D scores of each group were used to determine whether there was evidence of implicit dehumanizing biases. These results are also displayed in Table 1. As predicted, the D scores in the disgust condition were significantly greater than 0, indicating that disgusted participants were significantly faster in trials with the “Them + Animal” response key pairing than the “Them + Human” pairing. The D scores of the sad and neutral control conditions were also significantly greater than 0.

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Table 1.

Dehumanization IAT response latencies and implicit bias scores by condition.

Condition	N	Them + Human		Them + Animal		Dehumanizing		95% CI
		Pairing		Pairing		Bias (D)
		M	SD	M	SD	M	SE
Disgust	32	823.95	208.71	675.62	126.66	.43	0.07	[0.30, 0.56]
Sadness	32	868.90	295.53	756.47	162.22	.21	0.07	[0.08, 0.34]
Neutral	30	895.65	325.88	764.13	209.91	.28	0.07	[0.15, 0.41]

Note. Values in the “Them + Human” column are mean response latencies (in ms) and standard deviations for trials with incompatible response key pairings. Values in the “Them + Animal” column are for trials with compatible response key pairings. D scores represent estimated marginal means when controlling for the order of the combined test blocks. D scores are coded so that positive values indicate an implicit bias toward associating the outgroup with animals and the ingroup with humanity. Values in the 95% CI column are confidence intervals testing whether D is significantly different from 0 when holding task order constant.

Planned orthogonal comparisons tested whether participants in the disgust condition demonstrated greater dehumanizing biases than those in the sad and neutral conditions when controlling for the order of the combined test blocks. As expected, the IAT D scores were significantly greater in the disgust condition than in the sad and neutral control conditions, t(90) = 2.32, p = .023, d = 0.49. In contrast, the sad and neutral conditions did not differ in the magnitude of their dehumanizing biases, t(90) = 0.74, p = .46, d = 0.16. Figure 1 displays this pattern of means, with the strongest dehumanizing biases occurring in the disgust condition.

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Figure 1.

Mean IAT dehumanizing bias as a function of mood induction condition when holding block order constant.

Discussion

This study examined the influence of incidental disgust on outgroup dehumanization using a modified version of the Implicit Association Test (IAT; Greenwald et al., 1998) and a minimal-groups paradigm. In line with previous findings (e.g., Viki et al., 2006), all participants demonstrated a dehumanizing bias whereby outgroup members were more strongly associated with animals than were ingroup members. Feelings of disgust, however, significantly potentiated this dangerous cognitive bias. This effect was distinct from sadness, which showed little influence on dehumanization, suggesting that the observed effect of disgust on dehumanization is not due to negative valence priming. Our results therefore show both a general tendency to dehumanize members of arbitrary, minimal outgroups, and potentiation of that tendency via incidental disgust.

Although preliminary, these findings provide the first direct evidence that feelings of disgust can shift the human–animal boundary in social cognition, thus empirically linking it to the psychological machinery of outgroup dehumanization. Given that the mechanisms behind dehumanization have been relatively unexplored, we hope that our findings will encourage further investigations of this important topic. Deeper understanding of how disgust promotes dehumanization might lead to novel interventions for defusing intergroup violence (Hodson & Costello, 2007).

The current research is also one of the first to evidence dehumanizing associations using minimally created groups. Interestingly, although the dehumanizing biases were greatest in disgusted participants, all participants found it easier to associate outgroup members with animals, relative to ingroup members. This is notable because the minimal-groups paradigm ensured that they had no prior attitudes toward the group members. Interpersonal similarity, merely with respect to a previously unknown and unvalued tendency (i.e., “overestimation”), was sufficient to initiate an implicit dehumanization process. These results are consistent with those of Demoulin et al. (2009), who found evidence of explicit infrahumanization toward a minimal outgroup when the groups were formed by meaningful criteria. Thus in addition to documenting a causal role for disgust, this study adds implicit dehumanization to the array of intergroup biases that are activated by the most minimal—but meaningful—conditions of interpersonal similarity. Given that Demoulin et al. (2009) found that group meaningfulness was necessary for outgroup infrahumanization to emerge, it is possible that disgust works by imbuing greater meaningfulness to ingroup–outgroup distinctions (e.g., via the threat of disease). This emotional charging of group categorization may be a key component of the mechanism through which disgust influences dehumanization processes.

It is important to note that our findings are limited to IAT effects, which unfortunately do not distinguish between “outgroup dehumanizing” and “ingroup humanizing” biases. This is an inherent limitation of the IAT methodology. Since ingroup enhancement and outgroup derogation motives are not necessarily equivalent (Brewer, 1999), either or both may be involved in the effect found here. It is possible that disgust does not strengthen associations between outgroups and animals, but instead creates a stronger association between the ingroup and humanity. This would suggest that disgust reaffirms people’s unique humanity and extends it to similar others, at the expense of outgroup members. Additional studies using methods other than the IAT are necessary to resolve whether disgust promotes enhanced ingroup humanization, outgroup dehumanization, or both.

A second limitation is that the sadness and disgust manipulation check ratings were lower than expected, despite being significant in the appropriate directions and having large effect sizes. This was disappointing because the induction techniques have been successful at inducing moderately strong emotional states in previous research (e.g., Baumann & DeSteno, 2010; DeSteno et al., 2004; Moretti & di Pellegrino, 2010). We believe that the low ratings are likely due to a combination of two factors. First, an unfortunate choice of manipulation check scale anchors (1 corresponded to both “not at all” and “very little”) likely shifted scores to the low ends of the scales. Secondly, the ratings were completed at the end of the experiment when the effects of the emotion inductions were likely greatly diminished. These two factors may explain the low ratings. At the same time, it is also possible that the low ratings indicate that the manipulation failed to produce emotional states (i.e., a lack of “hot,” affective priming), but instead primed semantic associations involving disgust and sadness (“cold,” cognitive priming). ³ If this is correct, our findings carry a slightly different interpretation: exposure to concepts involving disgust facilitates dehumanizing associations in social-cognition without the recruitment of emotional architecture. Although the affective route seems more intuitively compelling, conceptual priming may be at least part of the story, if not the whole story, here. Unfortunately, it is often hard to disentangle these two processes, and even widely used implicit measures—such as the affective priming procedure (AMP; Payne, Cheng, Govorun, & Stewart, 2005)—have been subject to recent debate over the affective or conceptual nature of their effects (Blaison, Imhoff, Hühnel, Hess, & Banse, 2012). It would nonetheless be valuable to conduct a follow-up study with a more clearly conceptual manipulation (e.g., a sentence-unscrambling task) to examine whether semantic primes produce similar results.

It is also unclear whether the effects of disgust on dehumanizing associations are distinguishable from that of all other negative emotions. We evaluated sadness as a negative affect control, yet some might argue that a more stringent control would be anger or contempt. However, the effects of anger and contempt may prove very difficult to distinguish from that of disgust. All three are highly moralized other-condemning emotions (Haidt, 2003). Induced feelings of anger have also been shown to increase heuristic-based processing in social perception (Bodenhausen, Shepard, & Kramer, 1994), strengthen biases toward dispositional attributions of behavior (Keltner, Ellsworth, & Edwards, 1993), and cause implicit negativity toward outgroups (DeSteno et al., 2004). Consequently, we concede that anger and contempt may elicit dehumanization effects that are indistinguishable from that of disgust. On the other hand, anger and disgust are motivationally distinct. Anger is strongly associated with cognitive and behavioral approach (e.g., rumination, reactive aggression) whereas disgust is strongly associated with the opposite (Haidt, 2003). Indeed, dispositional disgust sensitivity is negatively associated with aggression for this very reason (Pond et al., 2012). The contexts that elicit anger and contempt are also clearly distinguishable from those that elicit disgust (Haidt, 2003; Hutcherson, & Gross, 2011). Therefore, if other condemning emotions like anger and contempt prove relevant to dehumanization processes, their differences from disgust may influence the form that dehumanized cognition takes. Anger-evoking contexts may entail more agentic forms of dehumanization, while disgust-evoking contexts may entail more self-protective, exclusionary forms of dehumanization. Future studies should examine whether anger and contempt can induce implicit dehumanization, and determine how and when their dehumanizing effects differ from those of disgust.

Follow-up studies could also employ other types of emotion manipulations; for example, the use of smells, movies, or emotional music. This would be particularly helpful for ruling out the possibility that disgust facilitated dehumanization more strongly than sadness simply because the disgust photographs contained less human stimuli than the sadness photographs (see the Method section for a description of the stimuli). The photo presentation was only a small part of the disgust manipulation—and the disgust writings largely involved human body products and people doing disgusting things—so this explanation may not be likely. Still, it is desirable to evaluate this and other possible alternative explanations for the effects seen here.

Conclusion

Tolerance and inclusive compassion are increasingly important in the ethnically and socially diverse communities of the 21st century. Accordingly, an important goal of psychological research is to identify social-cognitive biases that impede positive regard toward outgroups and the causal mechanisms that underlie those biases. The current research highlights a previously unarticulated effect of disgust on the most morally dangerous of intergroup biases: dehumanized perceptions of outgroup members. Further exploration of disgust’s function in shifting the human–animal boundary in social cognition will enrich our understanding of dehumanization and its all too commonly tragic role in intergroup violence.