Is there a link between the crafting of tools and the evolution of cognition?

The ability to craft tools is one of the defining features of our species. The technical intelligence hypothesis predicts that tool-making species should have enhanced physical cognition. Here we review how the physical problem-solving performance of tool-making apes and corvids compares to closely related species. We conclude that, while some performance differences have been found, overall the evidence is at best equivocal. We argue that increased sample sizes, novel experimental designs, and a signature-testing approach are required to determine the effect tool crafting has on the evolution of intelligence.