The role of cross-species relative brain size variation and time since domestication in explaining human empathy towards domesticated mammals

Although multiple publications have addressed the nexus between individual differences and attitudes towards nonhuman animals, fewer studies have discussed the rise of human-animal interactions, in particular with domesticated mammals, through an evolutionary lens. Two evolutionary hypotheses, the Symbiotic and Neurocognitive hypothesis, provide complementary predictions regarding the evolution of these cognitive and emotional mechanisms. According to the Symbiotic hypothesis, the longer the time humans have had to interact symbiotically with domesticated the animals, the greater their empathy towards them. Alternatively, the Neurocognitive hypothesis argues that human empathy directed at animals increases in response to the neural and cognitive complexity of nonhuman animals. To test these hypotheses, the present study reported questionnaire data from 322 Southwestern university students. These psychometric instruments measured the participants' levels of cognitive empathy (the attribution of mental states to animals), emotional empathy (emotional concern about animals), and harm avoidance (reluctance to mistreat animals) when rating 13 domesticated mammals. The species' times since domestication and relative brain sizes were then used as predictors of cognitive empathy, emotional empathy, and harm avoidance. The results of Linear Mixed and Hierarchical General Linear Cascade Models found empirical support for the Symbiotic and Neurocognitive hypotheses.