Gesell and his colleagues documented a set of behavioral norms that illustrate sequential & predictable patterns of growth and development.
[6] According to Gesell, the rate at which children develop primarily depends on the growth of their nervous system, consisting of the complicated web of nerve fibers, spinal cord, and brain.
Gesell opposed efforts to teach children things ahead of their developmental schedule, asserting that once the nervous system had matured adequately, a child would begin mastering tasks such as sitting up, walking, and talking from their own inner urges.
Gesell created the term "reciprocal interweaving" to describe the developmental process in which two opposite tendencies gradually reach an effective balance.
Gesell believed that developmental progress requires temporary loss of equilibrium, but is followed by reintegration at higher levels of organization.
He interpreted development as a process where behavior advances in a spiral pattern, alternating between equilibrium and disequilibrium as children enter new phases.
He directed parents to look to the children themselves for cues on how to help the child develop as an individual, and to set aside their own expectations of what the baby “ought” to be doing,[14] particularly in the first year of life.
[15] He believed that parents familiar with these sequences will become more patient and understanding during times of disequilibrium and instability [16] knowing that they will eventually disappear.
In addition, Gesell’s research was limited to middle-class children in a university setting [11] so critics are hesitant to generalize his findings to other cultures.
[5] Recent research has challenged Gesell's age norms, showing that newborns may have more abilities than was reported and that his developmental picture may be too slow.