Morgan's ghosts: On canon, cognition, and what we still do not know

Comparative psychology has its share of historical ironies. A particularly delightful one comes from Lloyd Morgan himself. In Animal Behavior, which was published after An Introduction to Comparative Psychology (which contains Morgan's Canon), he marvels at a digger wasp that picks up a small pebble in her mandibles and uses it as a hammer to pound and tamp the earth sealing her burrow. what does the Canon mean to the scientists who use it today? A recent article in this issue by Voudouris et al. (2025) gives us a first empirical insight. Using systematic surveys, they shed light on what comparative cognition researchers actually think about Morgan's Canon, the associative-cognitive distinction, and the role of parsimony in interpreting animal behavior. Morgan's Canon began as a plea for rigor. Over time, it became a slogan, sometimes a straitjacket, occasionally a scapegoat. But it remains also a guardrail, a guide, and a goad: it guards against overreach, guides control design and interpretation, and goads us to spell out mechanisms. The new survey shows that researchers still value the Canon but use it with more flexibility and less dogmatism than in the past. (PsycInfo Database Record (c) 2025 APA, all rights reserved).