Diagram showing one sequence of causally irrelevant and necessary actions used by an adult demonstrator to remove a reward from the puzzle object in Horner and Whiten [19•]. (a) During the causally irrelevant actions (yellow background), a bolt on top of the puzzle object was (i) hit with the tool then (ii) pushed aside, revealing a hole leading to an empty upper compartment. (iii) The tool was inserted into this hole. The demonstrator then immediately continued on to the actions that were actually necessary for retrieving the reward (blue background). (iv) An opening on the front of the box was uncovered by lifting a door, (v) then the tool was inserted into this opening and (vi) used to extract the reward. (b) When the walls of the puzzle box were transparent such that the irrelevance of steps i–iii was obvious (see photo), chimpanzees tended to reproduce only the causally necessary actions. By contrast, children showed a strong tendency to precisely imitate the entire demonstrated sequence. Puzzle object diagrams and photo reproduced with permission.