The course of induced crying activity in the first year of life

Abstract

In the first year of life the crying response to painful stimulation varies with age, or more precisely as a function of those psychophysical processes which underlie changes in age. At 5 hr of age crying reactivity is depressed from earlier age levels. It then increases at 2 days of age, remains relatively stable to 12 weeks of age, and thereafter diminishes markedly. Although the reliability coefficients from age to age show little or no stability of relative position for individual subjects, the course of crying reactivity generally shows significant differences from age group to age group. That the course of the cry reaction curves is primarily a function of age is supported by additional findings reported here which rule out as major determinants systematic adaptation effects, sex differences, and gross differences in IQ levels within the group studied. Speculation since crying activity, in one form or another, has been used as a response measure in many research investigations, the present study will offer guidelines regarding expected cry reactions from normal infants at a given age level. This study should make clear to the clinician that the same criteria cannot be used to evaluate the cry across the entire span of the first year of life. The same cry response, or lack of it, may be expected at one age and not at another. Since neurologic examinations frequently include response to painful stimulation, the age of the subject, with regard to the type of response studied here, becomes a critical factor in the diagnostic situation. © 1974 International Pediatric Research Foundation, Inc.