第一胎生的小孩「更聰明」，因為來自父母的額外心理刺激

First-born children are more intelligent than their siblings because they receive more mental stimulation in their early years, new research has shownFirst-born children are more intelligent than their siblings because they receive more mental stimulation in their early years, new research has shownFirst-born children are more intelligent than their siblings because they receive more mental stimulation in their early years, new research has shown