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People like attributing human characteristics to non-human beings and things. We’ve been doing it since we first started depicting gods in our own image. In a new study, published in the journal Current Directions in Psychological Science, psychologists Adam Waytz from Harvard University and Nicholas Epley and John T. Cacioppo from the University of Chicago set out to determine what drives our tendency toward anthropomorphism—or interpretation of non-human stuff in terms of human attributes—and inversely, our capacity for dehumanization, when we treat fellow humans as animals or objects.

Examples of our affection for anthropomorphism abound in the world around us, Waytz and colleagues write:

“… from pets that can seem considerate and caring, to gods that have goals and plans for one’s life, to computers than can seem to have minds of their own. People show an impressive capacity to create humanlike agents—a kind of inferential reproduction—out of those that are clearly nonhuman… People ask invisible gods for forgiveness, talk to their plants, kiss dice to persuade a profitable roll, name their cars, curse at unresponsive computers, outfit their dogs with unnecessary sweaters, and consider financial markets to be “anxious” at one moment and “delirious” the next.”

Cruel examples of dehumanization aren’t difficult to find throughout human history either, the authors point out:

“The Khmer Rouge, for instance, described their victims as ‘worms,’ Nazi propaganda depicted Jews as vermin, and Rwandan Hutus described the Tutsi as ‘cockroaches.'”

But what is it about different circumstances that drives these disparate tendencies? Waytz, Epley and Cacciopo’s argue that anthropomorphism hinges on two major motivational factors: the desire for social engagement, and the desire to be an effective participant in social situations. Extreme loneliness can often cause people to create their own version of human companionship. The researchers cite the extreme example of a woman who named and “fell in love” with a home stereo system. Yet, a more commonplace version of humanization as an antidote to loneliness is our tendency to anthropomorphize our pets, they say. (Back to the doggy sweaters!)

The other type of motivation, desire for efficacy in society, is exemplified by the fact that environmentalists often use the term “Mother Earth,” or in the way that we give human names to hurricanes, the authors write. Referring to a major storm as Hurricane Andrew, instead of say, storm 95-B, “simplifies and facilitates effective communication to enhance public preparedness, media reporting, and the efficient exchange of information.”

What, then, drives the opposite tendency—toward dehumanization? To explain this, the researchers invert the motivations for anthropomorphism. That is, if isolation and loneliness drive us to give human characteristics to non-human things, then a strong social connection or sense of belonging can drive us to dehumanize outsiders from our group. The authors write:

“Historical examples of dehumanization, such as ongoing violence between the Palestinians and Israelis, the Nazis’ persecution of Jews during the Holocaust, and torture at Abu-Ghraib prison in Iraq, also suggest that perpetrators of dehumanization are often members of a socially cohesive in-group acting against an out-group. Social connection may have many benefits for a person’s own health and well being but may have unfortunate consequences for inter-group relations by enabling dehumanization.”

Additionally, if a need to be effective in society drives our tendency to humanize things (like giving names to hurricanes to more effectively raise awareness), then in situations in which power trumps the need to interact with others effectively, it becomes easier to objectify people, the authors suggest. To illustrate this, they point to a series of experiments showing that, when people held power over others, they were more likely to view them as a means of accomplishing their own goals, instead of considering their individual humanity.

Awareness of what drives our perception of “humanness,” they conclude, is critical to a broader understanding of how we protect and preserve human rights. The most important aspect of anthropomorphism, they say, is that “perceiving an agent to be human renders it worthy of moral care and consideration.” For example, they cite a study in which radiologists were given a photo of a patient along with his or her test results. Compared with doctors who hadn’t seen a photo, those who had were more likely to express empathy and convey more details about the results to patients.

In contrast, casting others as less than human effectively justifies wrongdoing against them, the authors say, citing an example of recent revitalization efforts in New Delhi that bulldozed city slums and left many people homeless. One person whose home was destroyed likened the experience to being treated like garbage—to being “picked up and thrown away,” Waytz et al write.

The implications of framing people, animals and objects in terms of humanity are evident in our day to day lives, from the harmless comfort that some people find in dressing up Fido, to the more dangerous and cruel examples of objectifying fellow humans. To that end, further research and a more careful understanding of how our framework influences the world around us is critical, the researchers argue. Few of us, they conclude, “have difficulty identifying other humans in a biological sense, but it is more complicated to identify them in a psychological sense.”