Babies see human hand behind ordered events

Experiments find that infants attribute actions to people

BALTIMORE — Just like adults, babies regard recurring patterns or events as the products of intentional human actions, researchers reported March 12 at the International Conference on Infant Studies.

This early tendency to assume that any order one sees must have been created on purpose gets amplified with age, said psychologist Lili Ma of the University of British Columbia in Vancouver, Canada. “Adults in many cultures infer rational agents, such as gods, from regularities that they see in nature.”

In a series of experiments, 9- to 10-month-olds first saw that either a mechanical claw or an adult’s hand could pick up yellow and red pingpong balls and drop them into a clear container. Then infants watched nine balls roll down a chute, one at time, into a transparent tube without knowing whether a person or the claw had inserted them.

Over 12 trials, balls sometimes rolled by in a regular pattern — say, three yellow, three red, three yellow, or two yellow, one red repeated three times — and at other times formed a random pattern. After each set of balls entered the tube, researchers removed a barrier to show either a claw or a hand poised above a container connected to the chute.

Babies looked much longer at a claw than at a hand after seeing regular patterns, the equivalent of a surprised double take at a violation of what they expected to see, Ma proposed. Infants gazed slightly longer at a hand than at a claw after seeing random patterns, but not long enough to suggest that they had any strong expectations about causes of random patterns.

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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