Do you remember exactly where you were when you learned of the Sept. 11 terrorist attacks? Your answer is probably yes, and researchers are beginning to understand why we remember events that carry negative emotional weight.

In the August issue of Current Directions in Psychological Science, a journal of the Association for Psychological Science, Boston College psychologist, Elizabeth Kensinger and colleagues, explain when emotion is likely to reduce our memory inconsistencies.

Her research shows that whether an event 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.

For example, after seeing a man on a street holding a gun, people remember the gun vividly, but they forget the details of the street. Functional Magnetic Resonance Imaging (fMRI), studies have shown increased cellular activity in emotion-processing regions at the time that a negative event is experienced.

The more activity in the orbitofrontal cortex and the amygdala, two emotion-processing regions of the brain, the more likely an individual is to remember details intrinsically linked to the emotional aspect of the event, such as the exact appearance of the gun.

Kensinger argues that recognizing the effects of negative emotion on memory for detail may, at some point, save our lives by guiding our actions and allowing us to plan for similar future occurrences. "These benefits make sense within an evolutionary framework," writes Kensinger. "It is logical that attention would be focused on potentially threatening information."

This line of research has far-reaching implications in understanding autobiographical memory and assessing the validity of eyewitness testimony. Kensinger also believes that this research may end insight into the symptoms of posttraumatic stress disorder.