Researchers from Germany have found no evidence that only children are more likely to display narcissistic traits than those who have siblings. The findings have been published in Social Psychological and Personality Science.

“In my research I am trying to understand how narcissism develops and how it affects social behavior and relationships. The idea of narcissistic only children sounds plausible to many people, so I wanted to test it,” explained Michael Dufner of the University of Leipzig, the corresponding author of the study.

An initial survey of 556 participants found that people — even only children themselves — tended to view only children as more narcissistic than those with siblings.

The researchers then analyzed data from the Innovation Sample of the Socio-Economic Panel, a nationally representative longitudinal study of households in Germany. That study included 233 only children and 1,577 people with siblings.

But the scores of narcissistic traits for only children were not significantly different from people with siblings.

“We analyzed a large and representative data set, took potential confounds into account, and distinguished between admiration and rivalry as two major dimensions of grandiose narcissism. Yet, the results indicate that only children are not more narcissistic than non-only children on either of the two dimensions and regardless of whether or not we controlled for covariates,” the researchers said.

“People believe that only children are more narcissistic than people with siblings, but that’s not true,” Dufner told PsyPost. “When policy makers discuss the downsides of low fertility rates, they should let go of the idea that growing up without siblings leads to increased narcissism.”

But like all research, the study includes some caveats.

“We only tested people from Germany and we can’t be sure how results would look like in other cultures,” Dufner said. “Our research exclusively dealt with grandiose narcissism and not with vulnerable narcissism or narcissistic personality disorder. Although existing stereotypes emphasize the grandiose aspects of narcissism, future research should test whether only children differ from non-only children in these more maladaptive forms of narcissism.”

The study, “The End of a Stereotype: Only Children Are Not More Narcissistic Than People With Siblings“, was authored by Michael Dufner, Mitja D. Back, Franz F. Oehme, and Stefan C. Schmukle.