Interpretations without justification: a general argument against Morgan's Canon

In this paper I critically discuss and, in the end, reject Morgan's Canon, a popular principle in comparative psychology. According to this principle we should always prefer explanations of animal behavior in terms of lower psychological processes over explanations in terms of higher psychological processes, when alternative explanations are possible. The validity of the principle depends on two things, a clear understanding of what it means for psychological processes to be higher or lower relative to each other (1) and a justification of a general preference for explanations that refer to lower psychological abilities (2). However, I argue that we cannot spell out the idea of a psychological scale in a way that claim (2) is satisfied. I start with the discussion of different interpretations of the notion of a psychological scale (Sect. 2). In Sect. 3, I discuss different possible strategies to justify any of those interpretations and argue that all of them fail. Finally, in Sect. 4, I generalize the argument for all possible interpretations of Morgan's Canon and propose an alternative strategy: We should base our interpretations of animal behavior on more general principles such as evidential support and explanatory power, as followed in other scientific domains.