Researchers at Southwest University in Chongqing, China examined 270 college students by scanning their brains and used standard tests of intelligence, creativity, and personality type to measure their creativity, IQ, and agreeableness. Half of the participants had no siblings.
Their MRI scans revealed that those who grew up as an only child were more creative and less agreeable than those with siblings because of the difference in the structure of their brain.
Only children had extra grey matter in the supramarginal gyrus, which is part of the brain associated with flexibility, imagination, and planning. There was also a difference between only children's and non-only children's parahippocampal gyrus, which helps manage emotional and mood regulation.
The authors of the study Junyi Yang and Xin Hou, both from the department of Psychology at Southwest University said in the Brain Imaging and Behavior journal: "Different family composition and size inevitably make only-children different from non-only-children.
"There are few studies that have focused on the topic of whether different family environments influence children's brain structural development and whether behaviour differentially has its neural basis between only-child and non-only-child status."
The study also found that children who grew up as an only child were less empathetic.
The researchers added: "Only children usually miss out on important opportunities to rehearse some of of the more complicated aspects of relationships."
