a1 Department of Psychology, University of California, Los Angeles, Los Angeles, CA 90095. firstname.lastname@example.org http://reasoninglab.psych.ucla.edu/ email@example.com http://reasoninglab.psych.ucla.edu/
a2 Department of Biology, University of Louisiana, Lafayette, LA 70560. firstname.lastname@example.org
We are in vehement agreement with most of Vaesen's key claims. But Vaesen fails to consider or rebut the possibility that there are deep causal dependencies among the various cognitive traits he identifies as uniquely human. We argue that “higher-order relational reasoning” is one such linchpin trait in the evolution of human tool use, social intelligence, language, and culture.