Babies jealous before they can crawl: York U study


TORONTO, October 20, 2008 -- A York University professor has uncovered evidence that infants as young as three months exhibit signs of jealousy, contrary to theories that it takes root during the Terrible Twos.

Maria Legerstee, a professor in York’s Department of Psychology, found that babies react negatively when their mother’s attention is distracted by an interloper, suggesting they have an emotional response to relations between others.

Legerstee’s study focused on infants of ages three, six, and nine months; their mothers sat close by as a female researcher interacted with them. Infants reacted negatively – looking sad, smiling less, and looking away – when the researcher demonstrated unwillingness to communicate. When the researcher was simply busy, infants didn’t mind. But when the researcher began to engage in conversation with mom, actively excluding baby, the result was surprising.

“Babies did not like that at all,” said Legerstee. “No matter the age, they got very upset and did all kind of things to get our attention. They kicked their legs, yelled out loud, and turned in their seats. I’ve never seen anything like it.” 

Jealousy, embarrassment, pride and guilt – what psychologists call “non-basic” emotions – are thought to develop during the second year of life.

“The established notion was that an emotion like jealousy is too complex for the basic cognitive abilities of infants,” Legerstee said. “Jealousy implies the formation of a social bond, and is a reaction to the presence of one who threatens this bond. Thus at three months infants are aware of other people. This is strong evidence that infants understand that motives or goals guide our communicative behaviour.”

The study is part of Legerstee’s broader research into infants’ socio-cognitive development.

“We’re trying to expand our knowledge of what infants are capable of understanding, at various stages,” said Legerstee.

The study will appear in the forthcoming Handbook of Jealousy: Theories, Principles, and Multidisciplinary Approaches, slated for publication in Fall 2009.

Media contact:
Melissa Hughes, Media Relations, York University: 416 736 2100 x22097,

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