Data and Code: Mental Template Matching as a Cultural Transmission Mechanism

Among humans, the cumulative evolution of technologies and traditions is claimed to be dependent on our unique capabilities for teaching, language and imitation. Examples of cumulative cultural evolution in nonhuman animals are rare. However, less elaborate cognitive mechanisms might allow some forms of cultural evolution in other species. Tool-making New Caledonian crows are exceptional in that they appear to have a material culture which has diversified and incorporated incremental improvements over time. However, these crows seem to lack the capacity for imitation, teaching or language. One possibility is that their varied tool designs could be culturally transmitted if these crows acquire a mental tool template from observing their parent’s tools, and then reproduce this template in their own manufacture – a process analogous to avian song learning. If this hypothesis is correct these crows should have the capacity for mental template matching. Here, we tested whether New Caledonian crows exhibit mental template matching in a novel manufacture paradigm. Crows were first trained to drop paper into a vending machine to retrieve rewards. They later learnt that only items of a particular size (large or small templates) were rewarded. At test, despite being rewarded at random, and with no physical templates present, these crows manufactured items that matched the size of the previously rewarded templates. Thus, New Caledonian crows possess the cognitive machinery for mental template matching: a mechanism that could support the cumulative evolution of material cultures among this species and others.