Body-size estimations in children six through fourteen: a longitudinal study.

Estimates of perceived and ideal body size were collected in 216 boys and girls ages 6 through 14 years. Video methodology was used to adjust the width of a life-size frontal image of the children. Longitudinal data were collected annually for three years, beginning at ages 6, 9, and 12. Three psychological methods were used, including the method of adjustment, staircase method, and adaptive probit estimation technique which permitted separate measures of the children's point of subjective equality and just noticeable difference values. The point of subjective equality is the body size which is subjectively equal to the child's perception of self. The just noticeable difference is the amount of change in body size necessary to detect the difference 50% of the time. Acceptable size boundaries were also measured, using the method of adjustment. Over-all, children were accurate in estimating their body width, with average overestimation of less than 2%. Overestimation decreased within each age group during the three years of the study. There were no differences between ages or sexes. Both point of subjective equality and just noticeable difference values decreased significantly during the three years of the study. The latter values significantly decreased as children became older. Body dissatisfaction (the discrepancy between perceived and ideal size) remained low for boys in all age groups. Girls' body dissatisfaction significantly increased across ages, beginning at age 9. Test-retest consistency of both perceived and ideal size judgments at intervals of one and two years were low. Acceptable boundaries in body width were similar between sexes and across age cohorts.