Achievement and intelligence certainly do not fulfill all the basic human needs. Every person needs love, companionship, acceptance, and social interaction. The nature of a singleton's interpersonal experience is that of loyalty and dedication. Typically, only children receive an enormous amount of love and attention from their parents and are used to reflecting that energy in return. This directly affects the needs and offerings when interacting with friends and relationship partners.
According to Lorna V.'s article in the British publication The Guardian:
The absence of siblings means that only children are used to relating to others with a high degree of intensity. Intensity is, in fact, what characterizes most relationships for adult only children. In terms of friendship, it's not that friendship is hard to come by, more that it's not taken lightly.
With this intensity, comes a desire for independence and solitude; as well as deeply felt emotions when rejection occurs. The results of these incidents are varied, ranging from healthy alone time, paranoia, over-indulgence and deviant behaviors. Again, the exact reaction depends on the person, history, and motivation. (Lorna, 2002; Salmon, 2002)
Increased maturity and hyper-adult behaviors persist as singletons travel through adulthood. A tendency exists to associate with persons to their senior and to act older than they are. Combine this tendency with intensity and loyalty, and a parental archetype develops. It is common for singletons to give advice, be protective, and become "like a parent" to their friends and relationship partners. The stability of the friendship, confidence, and sincerity make only children great life-long friends. Research shows that middleborn children become experts at non-kin relationships because they do not feel a great deal of familial obligation. (Roberts and Blanton, 2001) Only children, however, build strong friendships and become well versed in creating lasting non-kin relationships to provide a substitute for the siblings they never had. It is almost as if they are adding to their family.
Eventually only children might like to have an only child (or two or three children) of their own. An article by Cao Li of the China Daily discusses the only-child generation in China becoming parents. A survey administered provided results that only child parents made concerted efforts to excel and educate themselves in regards to their parenting skills. Only child parents but great importance in ready with their children as well as education their children on manners, values, and social conduct. "Nearly 80% of OCP's (only child parents) tend to frequently review their ways of dealing with their children." (Li, 2004) It seems as if there is a conscious awareness among only child parents on how they were raised, what advantages they had, what they would have done differently, and how they can best raise their child to be prepared for the world.