Babies Expect People to Act Efficiently

Adults expect others to behave rationally and efficiently in their simple, everyday actions — this is what enables us to predict the route someone will take walking on the sidewalk, for instance. Now, new research shows that infants hold the same expectations for the behavior of others.

Even within the first two years of life, infants expect adults to behave rationally, efficiently, and consistently, according to the research, which is published in the April 2013 issue of Psychological Science.

Psychological scientists Rose Scott of the University of California, Merced and Renée Baillargeon of the University of Illinois hypothesized that infants would focus longer on an event that is more effortful, because it is unexpected.

To test this, infants watched as an experimenter sat facing two identical toys. One of the toys was placed under a transparent cover and the other was not. Infants watched as the experimenter reached for the covered toy (the more effortful action) or the uncovered toy (the less effortful action).

As predicted, infants looked longer when the experimenter performed the more effortful action, suggesting that they expected the experimenter to choose the toy that was clearly visible and accessible.

These results were supported in second study, in which infants looked longer when the experimenter reached for the object that was mentally less accessible (i.e., hidden by an opaque cover) as opposed to the object that was mentally more accessible (i.e., transparent cover).

Together, these studies support the idea that infants have an expectation that people will act rationally and efficiently, and that infants are able to adopt the perspective of the person performing the action.

Scott, R., & Baillargeon, R. (2013). Do Infants Really Expect Agents to Act Efficiently? A Critical Test of the Rationality Principle. Psychological Science, 24 (4), 466-474. DOI: 10.1177/0956797612457395