Some intrusions in dietary reports by fourth-grade children are based on specific memories: data from a validation study of the effect of interview modality.

In dietary recall for a specified target period, an intrusion denotes an item reported eaten that was not consumed during that period. Intrusions may denote items available during the specified period, items consumed during other periods, or items from general knowledge of dietary intake. To investigate a cognitive basis of intrusions, we analyzed data from a dietary-reporting validation study in which 69 fourth-grade children were observed eating 2 school meals (breakfast and lunch) and interviewed that evening about that day's intake in person or by telephone. Of 450 items reported eaten for school meals, 82 were intrusions. Observations and school food service production records were used to determine whether items denoted by intrusions were available in school food service environments on the interview day, as many as 3 school days prior to the interview day, and the day following the interview. Availability of items denoted by intrusions decreased backward over days from the interview day, and decreased from the interview day to the following day. Among 40 children who reported at least 1 intrusion, mean number of intrusions (controlling for number of items reported) increased as interviews occurred later in the week. These results are consistent with the idea that some intrusions are based on specific memories of items encountered but not eaten during the target period, or encountered before the target period. Other intrusions are likely based on general dietary knowledge. It may be possible to design interview techniques to reduce the occurrence of intrusions that are incorrectly based on specific memories.