F and G have continued to exhibit a tendency toward undersocialization, but this has at times been rather a positive factor in the process of attaining ego identity during adolescence, especially for G, serving to protect him from unreasonable social pressures to conform to group behavior. In combination with other cases of severe deprivation, the case of F and G holds some interesting implications for theories of human development, particularly the notion of critical periods.
This principle can probably be applied to various other areas as well (For example, many instances of deprivation have been reported in which attachment occurs much later than normal.) And in the case of F and G, though they still could not walk at 5 and 6 years of age, they acquired the ability during the brief period of 1 week following rescue. Clearly, the organism must possess a self-regulating mechanism pertaining to development that is of a higher order than mere homeostasis. The problem remains to elucidate the conditions necessary to initiate and terminate this developmental state of hibernation (Fujinaga, 2001).
If these principles prove to be true, then at the very least, the concept of a critical period in the understanding of human development obviously needs to be reconsidered. This concept attained sudden recognition through the imprinting experiments of Lorenz (1935), but it was originally reported as a law of behavioral development in birds, and no evidence has been provided that it can be applied without alteration to the area of human development. The term "critical period" refers to a specific, inherent developmental period during which a stimulus condition determining in an all or nothing manner the development of a specific type of behavior must occur, lest that behavior not appear in the individual. It hypothesizes the existence of a firmly age-bound developmental period that controls the manifestations of a certain behavioral pattern or characteristic.
However, if we assume that the process of human development has a high degree of plasticity and potential for self-regulation, the relevance of a postulated age-bound critical period becomes limited. The existence of a functional preparatory system to support manifestation of certain behavior seems to be a more important factor than an age-bound developmental period
Interpersonal and social input or stimuli are important items in orienting the human organism towards normal development (Bower, 2003, 1999). In the case of F and G, even though they possessed the competence to walk, it was not manifested as performance until after their rescue and placement in a normal social environment.
The fact that children ordinarily learn to walk at about 12 or 14 months of age is thought to be due to maturation. However, in F's and G's case maturation had not yet occurred at 5 or 6 years of age. Thus, it may be not only because of maturation that children walk at 14 months of age; walking may also