Biomedical subjects

L V Hedges

Publications and source records attributed to L V Hedges.

4 recordsLinked to original sources

PubMed1992

Memory for day of the week: a 5 + 2 day cycle.

People use a variety of schemes to keep track of time. One such scheme is the week, with its 7 distinctly named days. This article examines memory for day of the week and its relation to memory for time of day and for elapsed time (number of days). Data are presented from a study in which people answered a set of interview questions about the time of occurrence of a particular event. Two issues are addressed. The first issue concerns the way different temporal schemes are organized in relation to each other in memory. Memory for day of the week is independent of other aspects of temporal memory. The second issue concerns whether the week is organized hierarchically into either weekday periods or weekend periods or both. The weekday period forms a distinct 5-day unit within the 7-day weekly cycle. The present data, together with those from the authors' earlier work, suggest that the time an event occurred is encoded in relation to a set of separate temporal scripts (e.g., daily and weekly) and that such scripts may be hierarchically organized.

Adult↗

PubMed1991

Categories and particulars: prototype effects in estimating spatial location.

A model of category effects on reports from memory is presented. The model holds that stimuli are represented at 2 levels of detail: a fine-grain value and a category. When memory is inexact but people must report an exact value, they use estimation processes that combine the remembered stimulus value with category information. The proposed estimation processes include truncation at category boundaries and weighting with a central (prototypic) category value. These processes introduce bias in reporting even when memory is unbiased, but nevertheless may improve overall accuracy (by decreasing the variability of reports). Four experiments are presented in which people report the location of a dot in a circle. Subjects spontaneously impose horizontal and vertical boundaries that divide the circle into quadrants. They misplace dots toward a central (prototypic) location in each quadrant, as predicted by the model. The proposed model has broad implications; notably, it has the potential to explain biases of the sort described in psychophysics (contraction bias and the bias captured by Weber's law) as well as symmetries in similarity judgments, without positing distorted representations of physical scales.

Adolescent↗

PubMed1990

When is a test result abnormal? Defining limits and risks.

Test results from "normal" and "non-normal" individuals frequently overlap. Individuals with test results near the region of overlap have a high risk of being misdiagnosed. We present a statistical method for quantifying the certainty of diagnoses and defining a normal range, and illustrate its application with a specific example from a Tay-Sachs disease carrier screening program. This method can be applied to any test result based on a continuous variable and is particularly well suited to screening programs where the risk or incidence of a disease is known. We use an inconclusive range to reduce the likelihood of incorrect diagnoses resulting from measurement error and borderline results. The limits of the normal, inconclusive, and nonnormal ranges are based on three considerations: (1) the probability of misdiagnoses, (2) the expected frequency of inconclusive diagnoses, and (3) the reproducibility of the test results.

Bayes Theorem↗

PubMed1990

Reports of elapsed time: bounding and rounding processes in estimation.

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.

Humans↗