In the first evidence of its kind to date, Yale researchers find that infants prefer individuals who help others to those who either do nothing, or interfere with others’ goals, it is reported today in Nature.

“This supports the view that our ability to evaluate people is a biological adaptation—universal and unlearned,” said the authors of the study.

The study included six-and-10-month-old babies whose preferences were determined by recording which of two actors they reached towards.

In the first experiment, infants saw a wooden character with large glued-on eyes known as “The Climber.” At first, the climber rested at the bottom of a hill. The climber repeatedly tried without success to make it up the hill and was then either helped to the top by a triangular character that pushed the climber from behind, or hindered by a square character that pushed the climber down the hill.

During the test phase—after the infants had sufficiently processed the events—the researchers measured the infants’ attitudes towards the helper and hinderer by seeing which characters they reached for. Fourteen of the 16 10-month-olds, and all 12 six-month-olds, preferred the helper. A second experiment ruled out the possibility that the infants were merely responding to the direction in which the figures were moving. In a third experiment, infants of both ages preferred a helper to a neutral party, and then a neutral party over one who hindered.

“The presence of social evaluation so early in infancy suggests that assessing individuals by the nature of their interactions with others is central to processing the social world, both evolutionarily and developmentally,” the authors stated.

The ability to tell helpful from unhelpful people, and to favor the former, said the authors, was undoubtedly essential in activities such as group hunting, food sharing, and warfare. These abilities may also provide the starting point for moral reasoning and the development of abstract concepts of right and wrong. The infants’ evaluations were based solely on what they witnessed as bystanders, and not on their own relationships or experiences with any of the figures.

The authors said the next step would be to determine the complexity of this understanding—for example, to explore whether infants prefer to interact with those who punish hinderers to those who reward them.

Karen Wynn, professor of psychology at Yale, was senior author of the study. J. Kiley Hamlin was lead author, and Paul Bloom, professor of psychology, was a third author.