When Donald Trump proposed that Ghazala Khan – the Muslim Goldstar mother of Captain Humayun Khan who was killed in Iraq – was not allowed to speak, ostensibly because of Muslim sexist control of women, he dehumanized Mrs. Khan. Interestingly, Trump dehumanized Mrs. Khan by assuming that Islam was responsible for her dehumanization thus projecting the issue to the foreground.

To “dehumanize” someone is typically thought of as portraying the other person as uncivilized and animal-like. It has historically been used to explain the psychological changes in individuals during times of war or atrocity. In order for genocide and mass murder to take place the perpetrator must see his enemy as less than human and thereby more deserving of being killed. And, dehumanization helps perpetrators justify their behavior since they are not taking the life of a “real” human being.

But in recent decades researchers have been more interested in subtle forms of dehumanization in which human characteristics (such as emotions) are denied to some other individual or group. This can happen on an individual as well as group basis. Freedom of expression, for example, is considered a natural “human” right and it is “dehumanizing” to deny the right. Most research is on racial and ethnic groups. For example, studies show that the association of one ethnic group with an animal (e.g. Blacks with apes) causes significant perceptual distortions such as the overestimation of children ages and criminal culpability. Such research helps explain police violence and the disparities of police violence toward different groups (for a review of dehumanization research see Haslam and Stratemeyer).

Immigrants and asylum-seekers are also dehumanized (Trump calling Mexicans coming over the border “rapists” and “drug dealers”) as well as an increasing number of groups such as psychiatric patients, homeless people, gay men, and older adults. Although dehumanization is related to stereotypes, they are not equivalent since it is possible to stereotype without dehumanizing and vice versa. Moreover, keep in mind that “super humanizing” someone is equally as dehumanizing since it defines them as “other than human.” The ascription of superhuman physical or sexual qualities to an ethnic group diminishes the recognition of their experience of pain and their capacities for sensitivity.

The consequences of dehumanizing are serious and persistent. More than a few studies report how dehumanization leads to increased punishment because offenders are considered less than human, as well as the endorsement of extralegal behavior such as torture for terrorists. Trump’s dehumanization of Mrs. Khan perpetuated a stereotype designed to challenge the authenticity of their sacrifice, and to categorize the Khans in such a way as to make them less deserving of sympathy. Individuals or groups who are dehumanized are assumed to be less worthy of respect and conciliation.

The combination of stereotypes and dehumanization makes for an explosive mixture producing distorted perceptions and easy justification of violence. But even in situations where violence is less implicated (the Trump example) there is a sort of psychological violence that makes it easier to overlook or ignore the potential for aggression and cognitive distortions.