Shifting human color memory

Persons who witnessed an automobile accident involving a green car were exposed to information that the car was blue. On a subsequent color recognition test, most subjects shifted their color selection in the direction of the misleading information and away from the actual perceived color. Shifting was greater for subjects who did not initially commit themselves to a color selection. Control subjects, who were not exposed to misleading information, distributed their chokes around the true color, and did not show a systematic color shift over time.     

On the time course of perceptual information that results from a brief visual presentation.

A briefly presented visual stimulus engenders an available-information function that lags behind the physical stimulus. We report two experiments that focus on the iconic-decay portion of this function, which falls to 0 over a 200-300 ms period following stimulus offset. In each experiment, to-be-reported digit strings were shown for varying durations followed by a noise mask at varying poststimulus intervals. We found the shape of the performance curve relating digit-report probability to stimulus exposure duration to be independent of stimulus-mask interstimulus interval. This finding is consistent with the proposition that the iconic-decay function's shape is independent of stimulus duration and allows us to identify this shape. We rejected exponential iconic decay for 6 of 8 observers; however, all observers' decay functions could be adequately fit by gamma decay, a generalization of exponential decay.     

A picture is worth a thousandp values: On the irrelevance of hypothesis testing in the microcomputer age

Hypothesis testing, while by far the most common statistical technique for generating conclusions from data, is nonetheless not very informative. It emphasizes a banal and confusing question (“Is it true that some set of population means are not all identical to one another?”) whose answer is, in a mathematical sense, almost inevitably known (“No”). Hypothesis testing, as it is customarily implemented, ignores two issues that are generally much more interesting, important, and relevant: What is thepattern of population means over conditions, and what are the magnitudes of various variability measures (e.g., standard errors of the mean, estimates of population standard deviations)? The simple expedient of plotting relevant sample statistics with associated variability bars is a substantially better way of conveying the results of an experiment. In today’s microcomputer environment, there are many relatively cheap and easily available applications that allow one to do this. I make some brief, informal comments about some of these applications.     

Eye fixations and memory for emotional events.

Subjects watched either an emotional, neutral, or unusual sequence of slides containing 1 critical slide in the middle. Experiments 1 and 2 allowed only a single eye fixation on the critical slide by presenting it for 180 ms (Experiment 1) or 150 ms (Experiment 2). Despite this constraint, memory for a central detail was better for the emotional condition. In Experiment 3, subjects were allowed 2.70 s to view the critical slide while their eye movements were monitored. When subjects who had devoted the same number of fixations were compared, memory for the central detail of the emotional slide was again better. The results suggest that enhanced memory for detail information of an emotional event does not occur solely because more attention is devoted to the emotional information.     

When personal history repeats itself: Decomposing memories for recurring events

Retrospective reports of personal events constitute the principal data source for much applied social science research. Such reports are known to be subject to biases and errors of inference. In health surveys, for example, events associated with chronic conditions are particularly likely to be under-reported (Jabine, 1987). In this series of studies we apply perspectives and tools from psychological studies of memory to the problem of understanding and improving reports of past untilization of health care. In two studies we found that subjects report using different strategies to answer questions about how often they have seen a doctor over the past 12 months, depending on the type of doctor's visit and its frequency. A third study, in which subjects' recall was checked against medical records, provided evidence that individual health events within a group of recurring, similar events are much less likely than non-recurring events to be recalled. In Experiment 4 we tested the efficacy of cognitively oriented intervention techniques designed to (1) help subjects decompose their molar memories of groups of similar events into individual events and (2) place all remembered health events into a personal timeline. The intervention more than doubled the proportion of recurring events on the medical record that was recalled. In addition, the proportion of events that could be dated, and the accuracy of dates provided, both rose.     

Encoding and use of detail information in picture recognition

Subjects participated in a yes/no picture recognition experiment in which exposure time varied from 50 to 1,000 msec at the time of initial study. Following each study trial, half of the subjects, the detail at study and test (ST) group, reported whether they had observed a detail in the picture that they thought might help in subsequent recognition. The other half of the subjects, the detail at test only (T) group, did not attempt to name details during study. All of the subjects reported at the time of each test picture whether they were basing their yes/no recognition response on a specific detail in the picture or on the picture's general familiarity. The data provided strong support for a model which assumed that (a) there is a constant probability of encoding a detail during each successive unit of time at study and (b) a detail is named at test either if it was encoded at study or with some bias probability. ST subjects showed superior recognition memory performance relative to T subjects. Within the context of the aforementioned model, this superiority stems from two sources: ST subjects encode details at a faster rate than do T subjects and an encoded detail provided a better discriminative feature for ST subjects.     

Semantic integration of verbal information into a visual memory

A total of 1,242 subjects, in five experiments plus a pilot study, saw a series of slides depicting a single auto-pedestrian accident. The purpose of these experiments was to investigate how information supplied after an event influences a witness's memory for that event. Subjects were exposed to either consistent, misleading, or irrelevant information after the accident event. Misleading information produced less accurate responding on both a yes-no and a two-alternative forced-choice recognition test. Further, misleading information had a larger impact if introduced just prior to a final test rather than immediately after the initial event. The effects of misleading information cannot be accounted for by a simple demand-characteristics explanation. Overall, the results suggest that information to which a witness is exposed after an event, whether that information is consistent or misleading, is integrated into the witness's memory of the event.     

Left to right: representational biases for numbers and the effect of visuomotor adaptation

Adaptation to right-shifting prisms improves left neglect for mental number line bisection. This study examined whether adaptation affects the mental number line in normal participants. Thirty-six participants completed a mental number line task before and after adaptation to either: left-shifting prisms, right-shifting prisms or control spectacles that did not shift the visual scene. Participants viewed number triplets (e.g. 16, 36, 55) and determined whether the numerical distance was greater on the left or right side of the inner number. Participants demonstrated a leftward bias (i.e. overestimated the length occupied by numbers located on the left side of the number line) that was consistent with the effect of pseudoneglect. The leftward bias was corrected by a short period of visuomotor adaptation to left-shifting prisms, but remained unaffected by adaptation to right-shifting prisms and control spectacles. The findings demonstrate that a simple visuomotor task alters the representation of space on the mental number line in normal participants.     

Lasting false beliefs and their behavioral consequences

False beliefs and memories can affect people's attitudes, at least in the short term. But can they produce real changes in behavior? This study explored whether falsely suggesting to subjects that they had experienced a food-related event in their childhood would lead to a change in their behavior shortly after the suggestion and up to 4 months later. We falsely suggested to 180 subjects that, as children, they had gotten ill after eating egg salad. Results showed that, after this manipulation, a significant minority of subjects came to believe they had experienced this childhood event even though they had initially denied having experienced it. This newfound autobiographical belief was accompanied by the intent to avoid egg salad, and also by significantly reduced consumption of egg-salad sandwiches, both immediately and 4 months after the false suggestion. The false suggestion of a childhood event can lead to persistent false beliefs that have lasting behavioral consequences.