The portrait of twins' relationships wasn't all bleak. Burlingham also saw that functioning as a unit can be beneficial. When, at 2½ years, Bessie showed proficiency at making plasticine ducks, Jessie, rather than trying to learn the skill herself, was happy to ask Bessie to make "me ducky too." Similarly, when one of the pair was challenged by another child or reproached by an adult, the second twin put aside her rivalry to defend her sister. The protected twin, for her part, was glad to let the other temporarily assume a superior role in the relationship. At such times, feelings of unity overrode feelings of rivalry.
Overall, however, Burlingham saw that it was necessary for a twin to carve out some sense of individual identity . Bessie and Jessie at times supported each other and at other times criticized each other persistently. Each seemed to seek her partner's approval as a single child asks for praise from a parent; they also seemed to separate more easily from each other when they were happy and enjoying what they were doing. Bert and Bill, by contrast, were so invested in each other, so engaged in copying each other, that they didn't develop appropriate social skills or a sense of separateness. Years later, psychologists described their fusion as a severe maladaptation.
Despite its subtlety of observation, Twins did not go without criticism. Clearly, children brought up in a group setting at the Hampstead Nurseries—away from their parents all or most of the time—weren't being raised under typical circumstances. Their mothers' prolonged absences may have distorted the twin relationship. Burlingham's work also focused only on the early years of childhood, paying little attention to the stages of development after the child begins elementary school. And then there was the problem that, like other studies that rely on close observation, Burlingham's small sample size left her open to the charge that her conclusions could not be generally applied.
Nonetheless, her work encouraged others to observe twin development, giving rise to a host of new studies. We now understand better the particular challenges that twins face at critical junctures in their developmental trajectory—and parents, psychologists, and teachers, knowing more about how to treat twins, can better help them enjoy the pleasures of twinship as well.
Burlingham herself offered only two pages of practical advice for parents. It amounted to a plea against extremes: Parents shouldn't break up their twins completely, she said, but they shouldn't let them relate primarily to each other, either. Instead she called for "a normal development of the tie to parents." That advice may seem unremarkable coming from a Freudian psychoanalyst, but any twin who remembers being gussied up in matching sailor suits and put on display probably yearns to have been treated "normally" a little more often.