{"fact":"Like chimpanzees, crows demonstrate an understanding of cause-and-effect, successfully using tools to retrieve food.","context":"In the laboratory, when presented with a variety of sticks of different lengths and food positioned in a tube such that a stick was required in order to reach the food, New Caledonian crows correctly chose the appropriate length and diameter of stick to push out the piece of food (Chappell & Kacelnik 2002, 2004).","source":"Nicola S Clayton; Joanna M Dally; Nathan J Emery, Social cognition by food-caching corvids. The western scrub-jay as a natural psychologist, 10.1098/rstb.2006.1992","index":286}