Sir.—We read with interest the article "Parental Estimate of Child's Developmental Level in a High-Risk Population" by Coplan in the Journal (1982:136;101-104). Some of the limitations of this study, as Coplan admits, are the racial and socioeconomic homogeneity of the study populations, the fact that all the parents were educated, and, hence, the difficulty of generalizing these findings to other populations. In this context, we consider it worthwhile to present some of the findings of our previous unpublished study, which was strikingly similar in design.1
Consecutive patients aged up to 15 years (mean age, 8.6 years) who came to our psychiatric hospital—based mental retardation clinic for the first time were studied. Children who had had developmental assessments earlier, elsewhere, were excluded. One or both parents, who accompanied the child, were asked the question, "In your opinion, how old would a normal child be who would have the same