A validation study of children's dietary reporting provided an opportunity to investigate whether cognitive ability is a source of systematic error in dietary recalls. From the fall of 2004 through the spring of 2007, fourth-grade children (n = 374) in Columbia, South Carolina, were observed eating school meals and interviewed to obtain 24-hour dietary recalls; subsequently, measures of dietary reporting error were calculated. The common factor extracted from 4 subject-area achievement tests (scores on which were provided by the school district for 362 children) was used as a measure of cognitive ability. For the 325 children who reported school meals that met the criteria to be reports about school meals, as cognitive ability increased, dietary reporting error decreased; the relation between cognitive ability and dietary reporting performance was stronger among girls than among boys. The mean cognitive ability for 37 children who reported no meals that satisfied the criteria for being reports about school meals was significantly lower than that for the 325 children who reported meals that satisfied these criteria. These findings indicate that cognitive ability is a source of systematic error in children's dietary recalls. More generally, the quality of epidemiologic survey data may depend systematically on the cognitive ability of respondents.

Objective: To compare two approaches to analysing energy- and nutrient-converted data from dietary validation (and relative validation) studies – conventional analyses, in which the accuracy of reported items is not ascertained, and reporting-error-sensitive analyses, in which reported items are classified as matches (items actually eaten) or intrusions (items not actually eaten), and reported amounts are classified as corresponding or overreported.Design: Subjects were observed eating school breakfast and lunch, and interviewed that evening about that day's intake. For conventional analyses, reference and reported information were converted to energy and macronutrients; thent-tests, correlation coefficients and report rates (reported/reference) were calculated. For reporting error-sensitive analyses, reported items were classified as matches or intrusions, reported amounts were classified as corresponding or overreported, and correspondence rates (corresponding amount/reference amount) and inflation ratios (overreported amount/reference amount) were calculated.Subjects: Sixty-nine fourth-grade children (35 girls) from 10 elementary schools in Georgia (USA).Results: For energy and each macronutrient, conventional analyses found that reported amounts were significantly less than reference amounts (everyP < 0.021; pairedt-tests); correlations between reported and reference amounts exceeded 0.52 (everyP < 0.001); and median report rates ranged from 76% to 95%. Analyses sensitive to reporting errors found median correspondence rates between 67% and 79%, and that median inflation ratios, which ranged from 7% to 17%, differed significantly from 0 (everyP < 0.0001; sign tests).Conclusions: Conventional analyses of energy and nutrient data from dietary reporting validation (and relative validation) studies may overestimate accuracy and mask the complexity of dietary reporting error.