Do Chimpanzees Respond When They Get More Than a Partner?

Chimpanzees are more likely to refuse a grape if their partner gets a cucumber. There is a difference there, I think, just because something significant doesn't necessarily mean that it's a large enough effect to mean anything. Peter Blake and Katie McCulloch have a lovely study on kids from seven different cultures. Kids from most cultures respond negatively when they get less than a partner. Their responses increased across age.