The dual nature of tools and their makeover.

Vaesen argues that functional knowledge differentiates humans from non-human primates. However, the rationale he provides for this position is open to question--with respect to both the underlying theoretical assumptions and inferences drawn from certain empirical studies. Indeed, there is some recent empirical work that suggests that functional fixedness is not necessarily uniquely human. I also question the central role of stable function representations in Vaesen's account of tool production and use.