Negative Emotion Enhances Memory Accuracy Behavioral and Neuroimaging Evidence

There have been extensive discussions about whether emotional memories contain more accurate detail than nonemotional memories do, or whether individuals simply believe that they have remembered emotional experiences more accurately. I review evidence that negative emotion enhances not only the subjective vividness of a memory but also the likelihood of remembering some (but not all) event details. I then describe neuroimaging evidence suggesting that engagement of emotion-processing regions (particularly the amygdala and orbitofrontal cortex) relates to the encoding and retrieval of details intrinsically linked to negative items. KEYWORDS—affect; amygdala; fMRI; memory distortion People experience many events that elicit emotional reactions: They greet loved ones at the airport, visit sick children at the hospital, and attend friends’ weddings. Such events often are remembered vividly, and for a while researchers believed that these emotional memories might be immune to disruption (Brown & Kulik, 1977). Over the past 30 years, research has demonstrated convincingly that emotional memories are not impervious to forgetting or distortion. However, whether emotion enhances the detail with which information is remembered or whether emotion simply biases a person to believe that they have retained a vivid memory continues to be debated. This issue is of central importance for characterizing emotion’s mnemonic influences. Suggestive evidence for people’s inflated confidence in emotional memories has come from studies asking participants to distinguish old (studied) from new (nonstudied) items and also to indicate whether they vividly remember something specific about the old items or simply know those items had been presented previously (Yonelinas, 2002). Emotional and nonemotional items sometimes are judged as old with equal accuracy, but emotional items are more likely to be judged to be remembered and not just known (Ochsner, 2000). This pattern could signify participants’ inflated confidence for emotional memories: Participants believe they remember the emotional items’ details, but there is nothing about their recognition-memory accuracy to suggest that they actually do remember the emotional information with more detail. However, such a pattern could also arise if emotion influenced the amount of detail remembered about each item but not the number of items remembered: Although participants are equally likely to remember emotional and nonemotional items, perhaps they remember emotional items with additional detail. To differentiate these alternative explanations, my colleagues and I (Kensinger, Garoff-Eaton, & Schacter, 2006) compared the effects of emotion on memory for general item features with emotion’s effects on memory for specific item details. After viewing negative and neutral objects (Fig. 1A), participants indicated whether items were identical to ones they had studied (same), shared the same verbal label but not the same visual details as a studied object (similar), or were unrelated to any studied object (new; Fig. 1B). This design could separate a person’s memory for a general type of item (calling a same item ‘‘same’’ or ‘‘similar’’ rather than ‘‘new’’) from their memory for the exact visual details of an item (calling a same item ‘‘same’’). Participants were more likely to remember the visual details of negative items compared with those of neutral items (Fig. 1C; red portion of bars). Importantly, this mnemonic enhancement for visual detail occurred even when there was no effect of emotion on the ability to recognize that a particular item type had been studied (Fig. 1C; total height of bars). In other words, emotion affected the likelihood that details were remembered about a studied item but did not affect the overall proportion of items remembered. These findings converge with other evidence to suggest that, although emotional experiences are not rememAddress correspondence to Elizabeth Kensinger, Department of Psychology, Boston College, McGuinn 510, 140 Commonwealth Ave., Chestnut Hill, MA 02467; e-mail: [email protected]. CURRENT DIRECTIONS IN PSYCHOLOGICAL SCIENCE Volume 16—Number 4 213 Copyright r 2007 Association for Psychological Science bered with picture-perfect accuracy (Neisser & Harsch, 1992), emotion can enhance memory for many details, including the color of the font in which a word was presented, the spatial location of a word on a computer screen, or whether information was visually presented or mentally imagined (reviewed by Mather, 2007). NEGATIVE EMOTION ENHANCES MEMORYACCURACY MORE THAN POSITIVE EMOTION DOES The results just described point to a role for negative emotion in boosting not only the subjective vividness of a memory but also the likelihood that event details are remembered. Although it would be simple to conclude from these studies that any emotional experience is likely to be remembered with additional detail, the story may not be so straightforward. The valence of an event (i.e., whether it is pleasurable or aversive) seems to be a critical determinant of the accuracy with which the event is remembered, with negative events being remembered in greater detail than positive ones. In tasks requiring people to indicate whether they vividly remember an event or simply know that it occurred, negative events tend to be ‘‘remembered’’ more often than positive ones (Ochsner, 2000). Negative items also are more likely to be remembered with specific details than positive items are: Although individuals are good at distinguishing same from similar negative items (Fig. 1C), they perform equally poorly when distinguishing same from similar positive or neutral items (Kensinger, Garoff-Eaton, & Schacter, in press). When examining what people remember about public events, negative emotion also appears to confer mnemonic benefits. Levine and Bluck (2004) asked participants who were either pleased or displeased with the verdict in the O.J. Simpson trial to indicate whether particular events had occurred during the trial. We (Kensinger & Schacter, 2006b) asked Red Sox and Yankees fans to report what they remembered about the final game of the 2004 playoff series, in which the Red Sox defeated the Yankees. In both of these studies, the valence of a person’s response to the event outcome did not affect the quantity of remembered information, but it influenced the likelihood of memory distortions. Individuals who were pleased about the O.J. Simpson verdict were more likely to falsely believe that something had occurred during the trial than were individuals displeased about the verdict, and the pleased individuals were confident in their inaccurate endorsements. Similarly, Red Sox fans, who found the outcome positive, showed more memory inconsistencies, and more overconfidence, than Yankees fans did (Fig. 2). These findings suggest that negative emotion can lead to fewer reconstructive-memory errors than positive emotion, consistent with evidence that individuals in a negative mood process information in an analytical and detailed fashion, whereas people in a positive mood rely on broader schematic or thematic information and ignore the details (Bless & Schwarz, 1999). EFFECTS OF NEGATIVE EMOTION ON MEMORY ACCURACY: IT’S ALL IN THE DETAILS Although a consideration of valence helps in understanding the effects of emotion on memory accuracy, another piece of the puzzle hinges on the realization that there are many types of Fig. 1. Memory performance for negative versus emotionally neutral items. Participants viewed a series of objects (A) and determined whether each would fit into a drawer. A couple of days later, participants were asked to distinguish objects that were the same as studied objects (identical) from objects that were similar to studied objects (sharing the verbal label but not the exact visual details) or that were new objects (nonstudied; B). The graph (C) shows the proportion of time that participants gave a ‘‘same’’ response to a same item (red portion of bars) or a ‘‘similar’’ response to a same item (blue portion of bars). Participants were equally likely to remember whether a particular type of negative or neutral object had been studied (e.g., to know whether a snake or a kettle had been studied; note that the overall height of the bars is equal for the negative and neutral items). However, participants were better at remembering the exact visual details of negative objects than of neutral objects (notice that the red portion of bars is higher for the negative items than for the neutral items). Thus, even when participants had a similar ability to recognize a general type of negative or neutral item, their ability to remember the exact visual details of the recognized objects was enhanced for the negative items. Data from Kensinger, Garoff-Eaton, and Schacter (2006). 214 Volume 16—Number 4 Negative Emotion Enhances Memory Accuracy