Survey questions often probe respondents for quantitative facts about events in their past: "During the last 2 weeks, on days when you drank liquor, about how many drinks did you have?" "During the past 12 months, how many visits did you make to a dentist?" "When did you last work at a full-time job?" are all examples from national surveys. Although questions like these make an implicit demand to remember and enumerate specific autobiographical episodes, respondents frequently have trouble complying because of limits on their ability to recall. In these situations, respondents resort to inferences that use partial information from memory to construct a numeric answer. Results from cognitive psychology can be useful in understanding and investigating these phenomena. In particular, cognitive research can help in identifying situations that inhibit or facilitate recall and can reveal inferences that affect the accuracy of respondents' answers.

This articledescribes a simple model of the effects of timeon memory. The model combines the effects of forgetting and telescoping where the event is remembered as occurring more recently than it did. The model is tested on behavior data for which validation information are available. The use of records and of aided recall are shown to have opposite effects on memory errors. Records reduce telescoping effects, but not errors of omission. Aided recall reduces omissions, but does not reduce and may even increase telescoping. The article also includes a discussion of other characteristics of the interview and the respondent that affect memory.

The present article concerns the way temporal information is represented in memory and the processes used in estimating when events occurred. In particular, we examine the sources of bias in reports of the time that has elapsed since a target event occurred. We find that reported times are less than actual times. Evidence is presented that this forward bias is not a result of misrepresentation of elapsed time in memory, but rather reflects two factors that arise in constructing reports from inexact information in memory. One factor is subjects' imposition of an upper boundary on reports, reflecting their notion of what would constitute reasonable answers to the question asked. This boundary truncates the distribution of reports, producing forward bias. The other factor is subjects' use of rounded (prototypic) values; these values, although stated in days, actually represent larger temporal categories (e.g., 14, 21, 30, 60 days ago). The distance between rounded values increases as the temporal categories become larger. Because of decreasing precision in memory and this increase in the distance between rounded values, a broader range of values is rounded down than up, thus producing forward bias.

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