In previous studies, dogs and chimps taught to open a box and retrieve a toy copied their teacher’s toy-seeking behavior only when it proved efficient. When the instructing adult added irrelevant actions, such as brushing a feather along the edge of the box before opening it, the animal trainees skipped them, doing only what was necessary to get to the hidden toy. But human children copied every detail, even the pointless brush of the feather.

“Animals focus on getting the job done,” explains Mark Nielsen, a psychologist at the University of Queensland in Brisbane, Australia. “Humans seem to almost forget about the outcome and copy everything we see.”