In both psychology and artificial intelligence, many prominent researchers believe that intelligence is at least partially modular, but there has been relatively little work unifying the psychological and AI perspectives on modularity. This talk begins with a model of transitive inference reasoning in non-human primates developed at Edinburgh by Mitch Harris and Brendan McGonigle and ends with a new theory of the neuroscience of learning. On the way, it ponders important questions such as whether production-rule systems really are any kind of model of natural intelligence.