I review a paper which is testing whether chimps can perceive weight, something that is apparently quite controversial in the comparative literature. I generally like the paper, but the real problem is that weight is not really the kind of thing we tend to perceive. Instead, we perceive affordances, and these are typically about properties such as inertia and size-with-respect-to-grip-size, etc. I discuss some fruitful ways to take this forwards.
Schrauf, C., Call, J., Fuwa, K., & Hirata, S. (2012). Do Chimpanzees Use Weight to Select Hammer Tools? PLoSOne, 7 (7) DOI: 10.1371/journal.pone.0041044