The Transience of Memory

The first of Schacter’s “sins” of memory is transience, which covers both rapid and long-term forgetting, as well as problems at the time of encoding that may contribute to transience. There are several problems with this account, not least of which is the fact that the next sin, absent-mindedness, would seem to be a cause of transience. Which, then, is the “original” sin?

A second problem is that the mechanisms underlying short and long-term transience may be quite different. Although Schacter tries to argue that information can simply be “lost” from long-term storage, it seems more likely that this loss results from a failure to specify the correct search cues. Short-term or rapid forgetting, on the other hand, often clearly results from the complete loss of information. For example, on tasks such as digit span (where all possible task-relevant cues are available to memory), some subjects can show almost instantaneous forgetting and yet intact long-term memory performanc. This dissociation underscores how different short and long-term forgetting actually are.

For these reasons, I have combined short-term forgetting and absent-mindedness into a single type of memory system failure, failures of maintenance. Failures of this memory system frequently result from lapses of attention (such as may occur in divided attention tasks). Other times, information may seem to “disappear” from consciousness; notably, these moments are often characterized by a lack of concentration. In both cases, information is no longer maintained online to guide behavior.

Another symptom of maintenance failure is impaired prospective memory. Prospective memory refers to our ability to "remember to remember." For example, early in the morning you might notice that you are nearly out of milk, and you decide to stop at the store on your way home from work. However, when the time comes and you're driving home from work, you completely neglect to stop and buy more. This is a classic failure of prospective memory. In what way might this arise from maintenance failure?

One obvious possibility is that you failed to maintain your plans for the duration of the day, and so this information was not immediately available to guide behavior when you drove past the store. Your plan to stop at the store may have even occurred to you while driving, but that information succumbed to the sin of transience, or in our terms here, failed to be maintained. However, it seems unlikely that we are constantly maintaining all our future plans in working memory; although prospective memory failures would likely be less common if this were the case, it seems like another aspect of memory may be at fault here.

The second possibility is that you failed to search your memory for "driving home," or some other search cue that may have prompted you to remember your plan to stop for milk. This, however, is not a symptom of maintenance failure. Instead, this is a failure of what I call "memory search," in which the relevant information is accessible in memory, but is not retrieved. As it turns out, this type of memory problem is by far the most common. Look out for tomorrow's post, which will explain how two simple types of memory search failure can explain the majority of human memory inaccuracy.

Note: This post is part 2 in a series of posts, in which I'll review and revise Schacter's "seven sins of memory" according to a new framework of memory failure, one that is both closer to neuroanatomy and wider in scope. Here is part 1.

Related Posts:
Active Maintenance and The Visual Refresh Rate
Models of Active Maintenance as Oscillation
Anticipation and Synchronization
Task Switching in Prefrontal Cortex