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Babies exhibit jealousy as early as three months: study
published November 8, 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.”

Legerstee, who heads the Centre for Infancy Studies at York University, is a renowned psychologist whose research examines how cognitive and social factors interact in the developmental process. She is co-editing a comprehensive new handbook on jealousy.

“The Handbook of Jealousy: Theories, Principles and Multidisciplinary Approaches” (Wiley-Blackwell Publishing) is being put together by Legerstee and her colleague Professor Sybil Hart, from the Department of Human Development & Family Studies at Texas Tech University.

The book takes on the ambitious task of unlocking the processes responsible for the unfolding of jealousy.

“It will be the first book of its kind,” says Legerstee. “There are handbooks on many scholarly disciplines, but there is no handbook on jealousy, until now, that covers the topics that this book does.”

The book will sketch a picture of jealousy, in its normative form, including its functions, origins and differentiation during infancy and childhood. The edited volume will be an interdisciplinary compilation of 20 papers and three commentaries. It will chart how jealousy unfolds and explore familial, cultural, cognitive and biological factors that drive jealousy’s developmental trajectory.

“The Handbook of Jealousy” will be published by Wiley-Blackwell and is slated for publication in Fall 2009.