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Dehumanization (or dehumanisation) describes the denial of “humanness” to others and is theorized to take on two forms: animalistic dehumanization, which is employed on a largely intergroup basis, and mechanistic dehumanization, which is employed on a largely interpersonal basis. Dehumanization can occur discursively (e.g., idiomatic language that likens certain human beings to non-human animals, verbal abuse, erasing one's voice from discourse), symbolically (e.g., imagery), or physically (e.g., chattel slavery, physical abuse, refusing eye contact). Dehumanization often ignores the target's individuality (i.e., the creative and interesting aspects of his or her personality) and prevents one from showing compassion towards stigmatized groups.
Dehumanization may be carried out by a social institution (such as a state, school, or family) or via an individual's sentiments and actions. Dehumanization can be unintentional, especially on the part of individuals, as with some types of de facto racism. State-organized dehumanization has historically been directed against perceived racial, ethnic, national, or religious minority groups. Other minoritized and marginalized individuals and groups (based on sexuality, gender, (dis)ability, class, or some other organizing principle) are also susceptible to various forms of dehumanization. The concept of dehumanization has received empirical attention in the psychological literature. It is conceptually related to infrahumanization, deligitimization, moral exclusion and objectification. Dehumanization occurs across several domains, is facilitated by status, power, and social connection, and results in behaviors like exclusion, violence, and support for violence against others.
In Herbert Kelman's work on dehumanization, humanness has two features: "identity"—a perception of the person "as an individual, independent and distinguishable from others, capable of making choices" and "community"—a perception of the person as "part of an interconnected network of individuals who care for each other." When a target's agency and community embeddedness are denied, they no longer elicit compassion or other moral responses, and may suffer violence as a result.
In Haslam’s review of dehumanization, he differentiates between uniquely human (UH) characteristics, which distinguish humans from animals, and human nature (HN), characteristics that are typical or central to human beings. His model suggests that different types of dehumanization arise from the denial of one sense of humanness or the other. Language, higher order cognition, refined emotions, civility and morality are uniquely human characteristics, that is, traits humans have that animals do not. Cognitive flexibility, emotionality, vital agency, and warmth are central to human nature. Characteristics of human nature are perceived to be widely shared among groups; every human has these traits, while uniquely human characteristics (e.g. civility, morality) are thought to vary between groups.
Animalistic versus mechanistic dehumanization 
According to Haslam, the animalistic form of dehumanization occurs when uniquely human characteristics (e.g. refinement, moral sensibility) are denied to an outgroup. People that suffer animalistic dehumanization are seen as immoral, unintelligent, lacking self-control and likened to animals. This has happened with Black Americans in the United States, Jews during the Holocaust, and the Tutsi ethnic group during the Rwandan genocide. While usually employed on an intergroup basis, animalistic dehumanization can occur on an interpersonal basis as well. The mechanistic form occurs when features of human nature (e.g. cognitive flexibility, warmth, agency) are denied to targets. Targets of mechanistic dehumanization are seen as cold, rigid, interchangeable, lacking agency, and likened to machines or objects. Mechanistic dehumanization is usually employed on an interpersonal basis (e.g. when a person is seen as a means to another's end).
Related psychological processes 
Several lines of psychological research relate to the concept of dehumanization. Infrahumanisation suggests that individuals think of and treat outgroup members as “less human” and more like animals. Specifically, individuals associate secondary emotions (e.g. disillusionment, admiration) that are seen as uniquely human, more with the ingroup than the members. Primary emotions (e.g. anger, sadness) are those that all sentient beings, be they animals or humans, experience, and are found to be more associated with the outgroup. Delegitimisation is when groups are categorized into extreme negative social categories which are excluded from treatment according to acceptable norms and/or values.”  Moral exclusion occurs when outgroups are subject to a different set of moral values, rules and fairness than are used in social relations with ingroup members. When individuals dehumanize others, they no longer experience distress when they treat them poorly. Moral exclusion is used to explain extreme behaviors like genocide, harsh immigration policies, and eugenics but can also happen on a more regular, everyday discriminatory level. In laboratory studies, people who are portrayed as lacking human qualities have been found to be treated in a particularly harsh and violent manner. Nussbaum (1999) identified seven components of objectification: "instrumentality," "ownership," "denial of autonomy," "inertness," "fungibility," "violability," and "denial of subjectivity". Neuroimaging studies have discovered that the medial prefrontal cortex, a brain region distinctively involved in attributing mental states to others, shows diminished activation to extremely dehumanized targets (those rated, according to the Stereotype Content Model, as low-warmth, low-competence, such as drug addicts or homeless people).
Factors facilitating dehumanization 
While social distance from the outgroup target is a necessary condition for dehumanization, some research suggests that it is not sufficient. Psychological research has identified high status, power, and social connection as additional factors that influence whether dehumanization will occur. If being an outgroup member was all that was required to be dehumanized, dehumanization would be far more prevalent. However, only members of high status groups associate humanity more with ingroup than the outgroup. Members of low status groups exhibit no differences in associations with humanity. Having high status makes one more likely to dehumanize others. Low status groups are more associated with human nature traits (warmth, emotionality) than uniquely human traits, implying that they are closer to animals than humans because these traits are typical of humans but can be seen in other species. In addition, another line of work found that individuals in a position of power were more likely to objectify their subordinates, treating them as a means to one’s own end rather than focusing on their essentially human qualities. Finally, social connection, thinking about a close other or being in the actual presence of a close other, enables dehumanization by reducing attribution of human mental states, increasing support for treating targets like animals, and increasing willingness to endorse harsh interrogation tactics. This is surprising because social connection has documented benefits for personal health and well-being but appears to impair intergroup relations.
Racial minorities and ethnic groups 
Dehumanization often occurs as a result of conflict in an intergroup context. Ethnic and racial others are often represented as animals in popular culture and scholarship. There is evidence that this representation persists in the American context with Black Americans implicitly associated with apes. To the extent that an individual has this dehumanizing implicit association, they are more likely to support violence against Black Americans (e.g., jury decisions to execute defendants. Historically, dehumanization is frequently connected to genocidal conflicts in that ideologies before and during the conflict link victims to rodents/vermin. Immigrants are also dehumanized in this manner.
Objectification and dehumanization of women 
Fredrickson and Roberts argued that the sexual objectification of women extends beyond pornography (which emphasizes women's bodies over their uniquely human mental and emotional characteristics) to society generally. There is a normative emphasis on female appearance that causes women to take a third-person perspective on their bodies. The psychological distance women may feel from their bodies might cause them to dehumanize themselves. Some research has indicated that women and men exhibit a "sexual body part recognition bias" in which women's sexual body parts are better recognized when presented in isolation than in the context of their entire bodies whereas men's sexual body parts are better recognized in the context of their entire bodies than in isolation. In men, automatically dehumanizing women as either animals or objects is associated with heterosexual men’s willingness to rape and sexually harass women and with more negative attitudes toward female rape victims 
The role of nations and governments 
Sociologists and historians often view dehumanization as central to some or all types of wars. Governments sometimes represent "enemy" civilians or soldiers as less than human so that voters will be more likely to support a war they may otherwise consider mass murder. Dictatorships use the same process to prevent opposition by citizens. Such efforts often depend on preexisting racist, sectarian or otherwise biased beliefs, which governments play upon through various types of media, presenting "enemies" as barbaric, undeserving of rights, and a threat to the nation. Alternatively, states sometimes present an enemy government or way of life as barbaric and its citizens as childlike and incapable of managing their own affairs. Such arguments have been used as a pretext for colonialism.
The Holocaust during World War II and the Rwandan Genocide have both been cited as atrocities predicated upon government-organized campaigns of dehumanization, while crimes like lynching (especially in the United States) are often thought of as the result of popular bigotry and government apathy.
Anthropologists Ashley Montagu and Floyd Matson famously wrote that dehumanization might well be considered "the fifth horseman of the apocalypse" because of the inestimable damage it has dealt to society. When people become things, the logic follows, they become dispensable - and any atrocity can be justified.
Dehumanization can be seen outside of overtly violent conflicts, as in political debates where opponents are presented as collectively stupid or inherently evil. Such "good-versus-evil" claims help end substantive debate (see also thought-terminating cliché).
In science, medicine, and technology 
Relatively recent history has seen the relationship between dehumanization and science result in unethical scientific research. The Tuskegee syphilis experiment and Nazi human experimentation on Jews are two such examples. In the former, Black Americans with syphilis were recruited to participate in a study about the course of the disease. Even when treatment and a cure were eventually developed, they were withheld from the Black participants so that researchers could continue their study. Similarly, Nazi scientists conducted horrific experiments on Jewish people during the Holocaust. Dehumanization of these groups justified the research. When this research came to light, efforts were made to protect participants of future research, and currently Institutional Review Boards exist to safeguard individuals from being taken advantage of by scientists.
In a medical context, the passage of time has served to make some dehumanizing practices more acceptable, not less. While dissections of human cadavers was seen as dehumanizing in the Dark Ages (see Medieval anatomy), the value of dissections as a training aid is such that they are now more widely accepted. Dehumanization has been associated with modern medicine generally, and specifically, has been suggested as a coping mechanism for doctors who work with patients at the end of life. Researchers have identified six potential causes of dehumanization in medicine: deindivudating practices, impaired patient agency, and dissimilarity (causes which do not facilitate the delivery of medical treatment) and mechanization, empathy reduction, and moral disengagement (which could be argued, do facilitate the delivery of medical treatment).
From the patient point of view, in some states in America, controversial legislation requires that a woman view the ultrasound image of her fetus before being able to have an abortion. Critics of the law argue that simply seeing an image of the fetus humanizes it, and biases women against abortion. Similarly, a recent study showed that subtle humanization of medical patients appears to improve care for these patients. Radiologists evaluating X-rays reported more details to patients and expressed more empathy when a photo of the patient’s face accompanied the X-rays. It appears that inclusion of the photos counteracts the dehumanization of the medical process.
Dehumanization has applications outside traditional social contexts. Anthropomorphism, perceiving mental and physical capacities that reflect humans in nonhuman beings, is the inverse of dehumanization, which occurs when characteristics that apply to humans are denied to other humans. Waytz, Epley, and Cacioppo suggest that the inverse of the factors that facilitate dehumanization (e.g. high status, power, and social connection) should facilitate anthropomorphism. That is, a low status, socially disconnected man without power should be more likely to attribute human qualities to pets or electronics than a high-status, high-power, socially connected woman.
Researchers have found that engaging in violent video game play diminishes perceptions of both our own humanity and the humanity of the players who are targets of the violence in the games. While the players are dehumanized, the video game characters that play them are likely anthropomorphized.
Democracy and “dignity of man” 
German philosopher and anthropologist of law Axel Montenbruck wrote that dehumanization is inextricably linked with both the “techniques of neutralization” (David Matza/Gresham Sykes) and to the obedience aspects of the Milgram-experiment and in a wider sense with Zimbardo's Stanford prison-experiment.
Montenbruck continues that in light of our common Western civilization, dehumanization is based on political Humanism, in terms of both Human rights and Western democracy. Each of them are grounded in the “dignity of man” aspect. Therefore its “negation” might be seen as dehumanization in our common Western sense. Furthermore, in light democracy criminal law might be reduced to the simple formula: violating a person means an act of dehumanization by taking “freedom, unfairly and inhumanely”. The reaction of a civilized Western society ought to be “taking freedom as well, but fair and humane”.
Other topics 
The propaganda model of Edward S. Herman and Noam Chomsky argues that corporate media are able to carry out large-scale, successful dehumanization campaigns when they promote the goals (profit-making) that the corporations are contractually obliged to maximise. State media, in democracies and dictatorships, are also capable of carrying out dehumanization campaigns, to the extent with which the population is unable to counteract the dehumanizing memes.
See also 
- Haslam, N. (2006), Dehumanization: An integrative review. Personality and Social Psychology Review, 10, 252–264. (open access)
- Moller, A. C., & Deci, E. L. (2010). Interpersonal control, dehumanization, and violence: A self-determination theory perspective. Group Processes & Intergroup Relations, 13, 41-53. (open access)
- Haslam, N., Kashima, Y., Loughnan, S., Shi, J., & Suitner, C. (2008). Subhuman, inhuman, and superhuman: Contrasting humans with nonhumans in three cultures. Social Cognition, 26(2), 248-258. doi:10.1521/soco.2008.26.2.248 (open access)
- Leyens JPh, Paladino MP, Rodriguez RT, Vaes J, Demoulin S, Rodriguez AP, Gaunt R. 2000. The emotional side of prejudice: the role of secondary emotions. Personality and Social Psychology Review 4(2): 186-197. (open access)
- Bar-Tal, D. (1989). Delegitimization: The extreme case of stereotyping and prejudice. In D. Bar-Tal, C. Graumann, A. Kruglanski, & W. Stroebe (Eds.), Stereotyping and prejudice: Changing conceptions. New York, NY: Springer.
- Opotow, S. (1990). Moral exclusion and injustice: An introduction. Journal of Social Issues, 46, 1–20. (abstract)
- Nussbaum, M. C. (1999). Sex and socialjustice. Oxford, England: Oxford University Press.
- Kelman, H. C. (1976). Violence without restraint: Reflections on the dehumanization of victims and victimizers. In G. M. Kren & L. H. Rappoport (Eds.), Varieties of psychohistory (pp. 282-314). New York: Springer.
- Bandura, A. (2002). Selective moral disengagement in the exercise of moral agency. Journal of Moral Education, 31, 101-119.
- Bandura, A., Barbaranelli, C., Caprara, G. V., Pastorelli, C. (1996). Mechanisms of moral disengagement in the exercise of moral agency. Journal of Personality and Social Psychology, 71,364-374.
- Bandura, A., Underwood, B., &Fromson, M. E. (1975). Disinhibition of aggression through diffusion of responsibility and dehumanization of victims. Journal of Research in Personality, 9,253-269.
- Harris, L. T., & Fiske, L. T. (2006). Dehumanizing the lowest of the low: Neuroimaging responses to extreme outgroups. Psychological Science, 17, 847–853.
- Harris, L. T., & Fiske, S. T. (2007). Social groups that elicit disgust are differentially processed in mPFC. Social Cognitive and Affective Neuroscience, 2, 45–51.
- Capozza, D., Andrighetto, L., Di Bernardo, G.A., & Falvo, R. (2012). Does status affect intergroup perceptions of humanity? Group Processes & Intergroup Relations, 13(3), 363-377.
- Loughnan, S., Haslam, N., & Kashima, Y. (2009). Understanding the relationship between attribute- based and metaphor-based dehumanization. Group Processes and Intergroup Relations, 12, 747–762.
- Gruenfeld, D.H., Inesi, E.M., Magee, J.C., & Galinsky, A.D. (2008). Power and the objectification of social targets. Journal of Personality and Social Psychology, 95, 111–127.
- Waytz, A. & Epley, E. (2012). Social connection enables dehumanization. Journal of Experimental Social Psychology, 48, 70-76.
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- O’Brien, G. V. (2003). Indigestible food, conquering hordes, and waste materials: Metaphors of immigrants and the early immigration restriction debate in the United States. Metaphor and Symbol, 18, 33–47.
- Fredrickson, B. L., & Roberts, T.-A. (1997). Objectification theory: Toward understanding women's lived experiences and mental health risks. Psychology of Women Quarterly, 21, 173-206.
- Gervais, S.J., Vescio, T.K., Förster, J., Maass, A., & Suitner, C. (2012). Seeing women as objects: The sexual body part recognition bias. European Journal of Social Psychology, 42, 743-753.
- Rudman, L.A. & Mescher, K. (2012). Of Animals and Objects: Men’s Implicit Dehumanization of Women and Likelihood of Sexual Aggression. Personality and Social Psychology Bulletin, 36(8), 734-746.
- Schulman-Green, D. (2003). Coping mechanisms of physicians who routinely work with dying patients. Omega: Journal of Death and Dying, 47, 253-264.
- Hague, O.S. & Waytz A. (2012). Dehumanization in Medicine : Causes, Solutions, and Functions. Perspectives on Psychological Science, 7(2), 176-186.
- Sanger, C. (2008). Seeing and believing: Mandatory ultrasound and the path to a protected choice. UCLA Law Review, 56, 351–408.
- Turner, Y., & Hadas-Halpern, I. (2008, December 3). The effects of including a patient’s photograph to the radiographic examination. Paper presented at Radiological Society of North America, Chicago, IL.
- Waytz, A., Epley, N., & Cacioppo, J.T. (2010). Social Cognition Unbound : Insights Into Anthropomorphism and Dehumanization. Current Directions in Psychological Science, 19(1), 58-62.
- Bastian, B., Jetten, J., & Radke, H.R.M. (2012). Cyber-dehumanization: Violent video game play diminishes our humanity. Journal of Experimental Social Psychology, 48, 486-491.
- Montenbruck, Axel (2010), Western Anthropology: Democracy and Dehumanization. 2nd edition,, Universitätsbibliothek der Freien Universität Berlin (open access), 60-66,74-75
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