Several weeks ago I devoted a post to the history of the concept of regression, and the way it's been used with respect to psychotherapy. I pointed out that much child behavior that's called regression-- things like thumb-sucking, bed-wetting, and clinginess-- is not necessarily just like the behaviors of younger children, but instead is expectable behavior for a child of a given age who is distressed or even traumatized. Acting "regressed" can be a very normal response to frustrating or frightening circumstances.
Beyond that, however, there are a lot of aspects in child development that involve alternating "progression" and "regression". Some of these were described in the ‘40s, ‘50s, and ‘60s by Arnold Gesell and his colleagues Louise Ames and Frances Ilg at the Yale Child Development Center. Gesell, Ames, and Ilg described periods of "progression" during which young children seemed relaxed and comfortable, in equilibrium with their environments. These typically lasted a few months, then gave way to other periods of "regression", which were characterized by negative emotion and difficulty in adjusting to events. Periods of "progression" and "regression" were described as occurring spontaneously rather than being caused by frightening or painful events, although of course bad experiences could also have disturbing effects.
Gesell, Ames, and Ilg felt that abilities like inhibiting impulses developed at different periods than their apparent opposites like "letting go", but that gradual maturation of both kinds of abilities was needed during the progress to adulthood. They applied these concepts to toilet-training, for example, noting that a person who is thoroughly toilet-trained can inhibit the impulse to urinate or defecate when that's appropriate, but can "let go" when the time and place are right. Gesell and his colleagues described the alternating successes and failures as children master toilet habits; there are periods of time when the child seems to have "forgotten" his or her training and frequently does not make it to the bathroom in time, but these alternate with periods when there are no "accidents" but the child spends an interminable time sitting on the toilet without being able to release. Parents tend to see the "accident" phase as regressive, but not to realize that the other situation also indicates immature and incomplete mastery of elimination.
More recently, developmental psychologists have explored other behaviors that seem to follow "progression" with "regression". One example of this pattern comes from the mastery of the spoken language. Toddlers usually show early correct use of irregular nouns and verbs. They know that one goose and another goose are "geese", and that if I'm running now, when I finish I will say I "ran". But after a few months we begin to hear errors from the same children, who speak of gooses, and tell us that they runned away. They seem to have regressed, in that they are making mistakes that they did not make when they were younger. But if we examine what they are actually doing, we can see that "gooses" too is progress. The children have made a big step in language mastery by figuring out that there are rules for making plurals or past tenses, and they now apply those rules across the board. It's only after further learning that they understand the exceptions to the newly-mastered rules. What appeared to be regression was really a step forward.
Some developmental psychologists (for example, Trevarthen, C., & Aitken,K. . Regulation of brain development and age-related changes in infants' motives: The developmental function of regression periods. In M. Heiman [Ed.], Regression periods in human infancy [pp. 107-184]. Mahwah, NJ: Erlbaum) have referred to Periods of Rapid Change (PRCs). These PRCs are times when infants are emotional and demanding, in ways that might be called "regressed" but might better be called "disorganized". Parents find PRCs challenging and frustrating, especially since they have often assumed that a period of "progression" is permanent, rather than just a step to be followed by another period of "regression". Trevarthen and Aitken have suggested that babies behave in demanding ways when they really need more social engagement to help them succeed in a developmental task. We adults have no way of knowing what the babies need until they "tell" us, so they must behave in attention-getting ways to make us co-operate. This pattern may be parallel to the extra crying and demands for food that accompany a physical growth spurt. But although we gladly respond to demands for more food (when we figure out the cues we're being given), it's less easy for us to see the connection between needing attention and growing mentally or socially.
The rule about babies seems to be that as soon as we, their caregivers, feel we can relax a little bit, some new need or developmental phase will crop up. (One example of this is the way babies sometimes sleep through the night at 5 or 6 months, but then begin to wake in the night again, and go on for some months in that way.) Toddlers, preschoolers, and even older children seem to follow a similar pattern, but because they need less constant care, it may not be so obvious to us as it is for infants. Periods of regressive or disorganized or challenging behavior come with this age range, however, and they seem to be part of the whole picture of maturation. In most cases, the caregiver didn't make the PRC happen, nor did the child cause trouble on purpose. Instead, development is like the weather, with sunny days and rainstorms alternating without our necessarily causing one or the other. Our best bet is to learn to enjoy the sunshine without expecting it to go one forever-- and to try to understand how "regression" fits the child's developmental needs.