L. Caviola, S. Schubert, G. Kahane, & N. S.Faber
Cognition
Volume 225, August 2022, 105139
Abstract
People routinely give humans moral priority over other animals. Is such moral anthropocentrism based in perceived differences in mental capacity between humans and non-humans or merely because humans favor other members of their own species? We investigated this question in six studies (N = 2217). We found that most participants prioritized humans over animals even when the animals were described as having equal or more advanced mental capacities than the humans. This applied to both mental capacity at the level of specific individuals (Studies 1a-b) and at the level typical for the respective species (Study 2). The key driver behind moral anthropocentrism was thus mere species-membership (speciesism). However, all else equal, participants still gave more moral weight to individuals with higher mental capacities (individual mental capacity principle), suggesting that the belief that humans have higher mental capacities than animals is part of the reason that they give humans moral priority. Notably, participants found mental capacity more important for animals than for humans—a tendency which can itself be regarded as speciesist. We also explored possible sub-factors driving speciesism. We found that many participants judged that all individuals (not only humans) should prioritize members of their own species over members of other species (species-relativism; Studies 3a-b). However, some participants also exhibited a tendency to see humans as having superior value in an absolute sense (pro-human species-absolutism, Studies 3–4). Overall, our work demonstrates that speciesism plays a central role in explaining moral anthropocentrism and may be itself divided into multiple sub-factors.
From the General Discussion
The distal sources of moral anthropocentrism
So far, we have discussed how the factors of moral anthropocentrism are related to each other. We now turn to briefly discuss what ultimate factors may explain moral anthropocentrism, though at present there is little evidence that directly bears on this question. However, evolutionary considerations suggest a preliminary, even if inevitably speculative, account of the ultimate sources of moral anthropocentrism. Such an explanation could also shed light on the role of the sub-factors of speciesism.
There is extensive evidence that people categorize individuals into different groups (cf. Tajfel, Billig, Bundy, & Flament, 1971), identify with their own group (Hornsey, 2008; Tajfel & Turner, 1979), and prioritize members of their ingroup over members of their outgroup (Balliet, Wu, & De Dreu, 2014; Crimston et al., 2016; Fu et al., 2012; Sherif, 1961; Yamagishi & Kiyonari, 2000; for bounded generalized reciprocity theory, cf. Yamagishi & Mifune, 2008). Ingroup favoritism is expressed in many different contexts. People have, for example, a tendency to favor others who share their ethnicity, nationality, religion, or political affiliation. (Rand et al., 2009; Whitt & Wilson, 2007). It has been argued that ingroup favoritism is an innate tendency since it can promote safety and help to encourage mutual cooperation among ingroup members (Gaertner & Insko, 2000). It seems, therefore, that there are good reasons to assume that speciesism is a form of ingroup favoritism analogous to ingroup favoritism among human groups.
While typical human ingroups would be far smaller than humanity itself, our similarity to other humans would be salient in contexts where a choice needs to be made between a human and a non-human. Since the differences between humans and animals are perceived as vast—in terms of biology, physical appearance, mental capacities, and behavior—and the boundaries between the groups so wide and clear, one would expect ingroup favoritism between humans and animals to be particularly strong. Indeed, research suggests that perceived similarity with outgroup members can reduce ingroup favoritism—as long as they are seen as non-threatening (Henderson-King, Henderson-King, Zhermer, Posokhova, & Chiker, 1997). Similarly, it has been shown that people have more positive reactions towards animals that are perceived as biologically, physically, mentally, or behaviorally more similar to humans than animals that are dissimilar (Burghardt & Herzog, 1989; Kellert & Berry, 1980).
