Developmental Psychology Describe the characteristics of individuals who are voluntarily childless, and their long-term happiness with the lifestyle.
Developmental Psychology has made attempts to analyze the adult population that chooses against having children, however, it is very hard to just generalize their overall personality because the latter is influenced by tons of variable environmental factors. This is what makes it difficult to correlate childless adults to the theories that we know.
For example, Erik Erikson in his psychosocial stages of development would argue that adults of "breeding" age (Young and Middle Adulthood ranging from 20-40 years of age) are looking for Intimacy versus Isolation, and then Generativity versus Stagnation.
Theoretically speaking, when an adult (20-30 years) hits the Intimacy vs. Isolation stage they want to love freely, make relationships that last and establish solid connections. The next stage over, Generativity versus Stagnation, would claim that the full adult wants to expand and extend this love toward others through agape, or by becoming parents.
However, a newer movement called the Childfree Life is showing a different perspective to this.
A study in 1981 (which is still used as a benchmark) on 44 voluntarily vasectomized non parents versus 51 vasectomized parents (males, of course) showed the following results
.....overall those who had chosen voluntary childlessness as a way of life had a greater capacity for independent thought, were less traditionalist than their counterparts in the parent group, and were more inclined toward experimentation
This study is at the heart of the DINK (double income, no kids) experience. The DINK is a movement where adults who choose to remain childless expose their personal side of the argument in hopes that the general population would get to know the other side of the idea of "family". There is a network online for this purpose.
The people who are part of the DINK network argue that their lives are no different in terms of wants and needs; that their primary focus is their own development as individuals and, should the moment ever come, they would welcome parenthood if this is indeed an appealing prospect.
Also, another hot topic in the Childfree movement is "The Female Assumption" which is a direct hit on the ideal of the female as the nurturing crux of the family. That women prefer to grow in ways other than as wives and mothers is a perfect example of what the Childfree movement wants to show: that people do not need to adhere to the principles and expectations of others based merely on tradition.
Therefore, those who are part of the network of people who prefer a childfree life simply shift their priorities and goals toward more personal issues rather than continue to extend a family. Ultimately, they lead normal lives because at all times they abide by their own principles and goals, and not those imposed by society or by their families.