Social dominance orientation connects prejudicial human–human and human–animal relations

• We test whether and why human–human and human–animal biases are related.
• We confirm that speciesism is associated with negative ethnic outgroup attitudes.
• Social dominance orientation (SDO) accounted for this association.
• Ideological individual differences (SDO) link inter-human and inter-species biases.

Recent theorizing suggests that biases toward human outgroups may be related to biases toward (non-human) animals, and that individual differences in desire for group dominance and inequality may underlie associations between these biases. The present investigation directly tests these assumptions. As expected, the results of the current study (N = 191) demonstrate that endorsing speciesist attitudes is significantly and positively associated with negative attitudes toward ethnic outgroups. Importantly, individual differences in social dominance orientation accounted for the association between speciesist and ethnic outgroup attitudes; that is, these variables are associated due to their common association with social dominance orientation that underpins these biases. We conclude that social dominance orientation represents a critical individual difference variable underlying ideological belief systems and attitudes pertaining to both human–human intergroup and human–animal relations.