New Delhi, Feb. 4: Preschoolers who spend time with each other tend to adopt specific sets of personality traits of those in their networks, a US study has suggested, pointing to what scientists say is evidence for contagion.

Children whose play partners were extroverted and hardworking displayed similar traits over time but children whose play partners were over-anxious and easily frustrated did not adopt these traits, the study by Michigan State University researchers has found.

"Our finding that personality traits are contagious among children flies in the face of common assumptions that personality is ingrained and can't be changed," Jennifer Neal, associate professor of psychology, said in a media release. "This is important because some personality traits help children succeed in life, others can hold them back."

Neal and her colleagues observed the classroom behaviour of 53 preschoolers, measuring displays and changes, if any, in what psychologists call sets of positive emotionality, negative emotionality, effortful control, and peer social play relationships over an entire school year.

Children with positive emotionality are likely to be happier, laugh faster, and easier to engage with, while children with negative emotionality appear gloomier and less easy to engage. Effortful control measures the ability to respond to stimuli such as questions posed or challenges encountered in the preschool environment.

The scientists found that children's traits shaped the formation of play relationships and that the traits of children's playmates shaped the subsequent development of the children's own traits. Their research findings appeared in the Journal of Personality and Social Psychology on Friday.

The researchers say their findings suggest that children have a bigger effect on each other than hitherto assumed.

"Parents spend a lot of their time trying to teach their child to be patient, to be a good listener, not to be impulsive," said Emily Durbin, associate professor of psychology and the study's co-investigator. "But this wasn't their parents or their teachers, it was their friends. It turns out three and four-year olds can be change agents."

An Indian psychologist said the US study appears to have captured evidence of what psychologists know as mirroring. "We've known that among those who spend time with each other can subconsciously take up certain behavioural traits," said Madhumati Singh, a senior psychologist at the New Delhi-based Samvedna Clinic.

"But personality traits may sometimes overlap - so some traits that preschoolers observe among their peers might also be present in parents," Singh, who was not associated with the study, told The Telegraph.

Three years ago, psychologists in the US found that preschool peers can have an impact on children's language abilities. A study by Laura Justice at the Ohio State University and her colleagues suggested preschoolers whose peers had relatively high language skills showed more improvement in their own language skills.

The 2014 study, published in the journal Psychological Science, had prompted scientists to speculate that when preschoolers play and interact with each other in classrooms, they imitate each other's behaviours.