"Because only children do not have siblings with whom to interact, they learn to be children on their own. Parents and play groups can help, but ultimately children become conditioned to depend on themselves. Says one adult only child, "Possibly the best part was developing the ability to enjoy being alone and to entertain myself. I've always had plenty of friends, yet people are surprised by how much of a loner I can be" (Koontz, 1989, p. 39). Although this self-sufficiency can have its benefits, it can also mean that only children are inherently alone as their personalities develop.
Because only children must develop in social situations that may not be suited to their personalities, the concepts of introversion and extraversion must be re-evaluated in the consideration of only children. Ultimately, an only child's environment forces him or her to take on both characteristics of introversion and extraversion despite natural inclinations to be one or the other. A naturally introverted child must show extraverted qualities if he or she wishes to make friends; likewise, a naturally extraverted child must learn to show introverted qualities by being content to focus on his or her own thoughts when playmates are unavailable."