Does our perception of animals shape when we see all humans as being created equally?

Thumbnail Image



Journal Title

Journal ISSN

Volume Title

Repository Usage Stats



Humans are paradoxical in their ability for extreme kindness and cruelty. The goal of this dissertation is to further uncover the psychological mechanism(s) that allow humans to accept harm directed at members of other groups. The human self-domestication hypothesis proposes that human unique forms of mentalizing evolved as a byproduct of selection for ingroup prosociality. Hare (2017) proposed that late in human evolution Homo sapiens bonded more closely with ingroup members and more skillfully read the mental states of others. Moral and cultural behaviors expanded, and modern human behavior emerged. However, more closely bonded groups tend to perceive outgroup strangers as more threatening. It became advantageous to deny some forms of human-unique mental states to individuals from threatening groups. In this way emotional and moral constraints on violence toward other humans can be escaped. The potential for lethal aggression and harm toward outgroup strangers became even more extreme as a result. According to this model there should be strong psychological links between group identity, mental state attribution, moral exclusion, and a willingness to harm others. Two main mechanisms have been proposed to provide this link. The first is dehumanization or the ability to deny fully human emotions and mental abilities to another person or group of people (Haslam, 2006). The second is social dominance orientation or the perception of a hierarchy between different human groups (Sidanius & Pratto, 2001). Together these mechanisms can override individual characteristics that lead to concern. Group identity alone can be used to indicate inferiority or less than human status. Moral exclusion and harm can follow. More recently a third moderating factor has been proposed. Costello & Hodson (2010) proposed that beliefs about animals strongly shape tendencies to dehumanize. Seeing animals as having human-like minds negates the negative impact of dehumanization since being nonhuman is so similar to being human. In Chapter 1, I combine this evolutionary model with the proposed mechanisms that drive the worst forms of group-based aggression to propose the Dehumanization of Inferior Groups (DIG) Hypothesis. The DIG hypothesis suggests the perception of other groups of humans is strongly modulated by how we view the minds of other animals, their relationship with each other and our relationship to them. Our minds evolved to distinguish between humans and animals, but we develop the ability to categorize some members of our own species as more animal-like. We also evolved to categorize the relative equality or inequality of different groups. This includes groups of animals that can be perceived as different but equal or ranked hierarchically. How we perceive different groups of animals will relate to how hierarchically we view different groups within our own species. The present dissertation seeks to provide initial tests of the DIG hypothesis. To do so, I used experiment-based surveys, investigating behavioral patterns of adults and school age children. In Chapter 2, I assessed dehumanizing tendency in adults and children, revealing that variety of humanness representations can elicit dehumanization in both age groups. Similar to the links seen in previous investigations of adults, children’s willingness to dehumanize is related to their acceptance that other groups can be inferior and more deserving of punishment. In Chapter 3, I examined the association between the perception of animal-to-human similarity and dehumanization. Results in adults and children showed that highlighting mental similarities between animals and humans could narrow down the perceived animal-human divide. However, in both age group, this manipulation does not attenuate dehumanization or the intergroup biases associated with it. Chapter 4 explored the association between the treatment of other human groups and the treatment of animals in a variety of participants who were engaged in different relationship with animals. I found that people who endorsed discrimination of dog breeds also endorsed group-based discrimination in human society. Moreover, positive contact with dogs is associated with disapproval of group-based inequality. Together, these findings suggest that the perception of human intergroup relations and the perception of relationship among animal groups are dependent upon similar cognitive processes. The studies presented here have implications for understanding psychological origins of dehumanization as well as designing interventions to promote intergroup tolerance.





Zhou, Wen (2022). Does our perception of animals shape when we see all humans as being created equally?. Dissertation, Duke University. Retrieved from


Dukes student scholarship is made available to the public using a Creative Commons Attribution / Non-commercial / No derivative (CC-BY-NC-ND) license.