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How ‘Cooties’ and ‘Crushes’ Are Encoded In Developing Brains

Researchers have found a signal in the brain that reflects young children’s aversion to members of the opposite sex — the “cooties” effect — and also their growing interest in the opposite sex as they enter puberty. Both responses are encoded in the brain structure called the amygdala, according to researchers at University of Illinois.

The amygdala was once thought of as a “threat detector,” said psychology professor Dr. Eva Telzer, who led the new analysis.

“But increasing evidence indicates that it is activated whenever someone detects something meaningful in the environment,” she said. “It is a significance detector.”

For the study, researchers evaluated 93 children’s attitudes toward same-sex and opposite-sex peers. Using functional MRI, which tracks how oxygenated blood flows in the brain, the researchers also analyzed brain activity in 52 children.

The finding that very young children pay close attention to gender is not a surprise, Telzer said.

“We know that there are developmental changes in terms of the significance of gender boundaries in young kids,” she said. “We also know about the whole ‘cooties’ phenomenon.”

That’s where young children develop an aversion to children of the opposite sex and act as if they could contaminate them with “cooties” if they get too close. Children at this age also prefer the company of their same-sex peers, she noted.

This phenomenon was reflected in the young children’s evaluations of each other.

“Only the youngest children in our sample demonstrated a behavioral sex bias such that they rated same-sex peers as having more positive (and less negative) attributes than opposite-sex peers,” the researchers wrote in the study, which was published in the Journal of Cognitive Neuroscience.

“And so we think the amygdala is signaling the significance of cooties at this developmental period,” Telzer said.

The interest in opposite-sex peers tends to wane in later childhood, just before puberty, Telzer said. The researchers saw no difference in the amygdala’s response to same-sex and opposite-sex faces in children between the ages of 10 and 12.

But in puberty, children’s interest in the opposite sex blooms. They may become infatuated with a member of the opposite sex, sometimes referred to as a “crush,” Telzer said.

“When puberty hits, gender becomes more significant again, whether it’s because your body is changing, or because of sexual attraction or you are becoming aware of more rigid sexual boundaries as you become more sexually mature,” Telzer said.

“The brain is responding very appropriately, in terms of what’s changing developmentally.”

Source: University of Illinois at Urbana-Champaign

Image Credit: Julie McMahon

How ‘Cooties’ and ‘Crushes’ Are Encoded In Developing Brains

Janice Wood

Janice Wood is a long-time writer and editor who began working at a daily newspaper before graduating from college. She has worked at a variety of newspapers, magazines and websites, covering everything from aviation to finance to healthcare.

APA Reference
Wood, J. (2018). How ‘Cooties’ and ‘Crushes’ Are Encoded In Developing Brains. Psych Central. Retrieved on December 4, 2020, from
Scientifically Reviewed
Last updated: 8 Aug 2018 (Originally: 12 Apr 2015)
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
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