Chimpanzees use weight to pick the best tool, and monkeys beg more when they’re paid attention to.
via ScienceDaily: Latest Science News http://www.sciencedaily.com/releases/2012/07/120718192005.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily+%28ScienceDaily%3A+Latest+Science+News%29