How do models of memory account for findings as diverse as these? And what do they tell us about the function of memory?
Cognitive neuroscience has made strides in answering these questions, and provides a good example of the benefits of collaboration between psychologists and other scientists.
The three different stages of memory, encoding, storage, and retrieval, are now known to be associated with activity in different parts of the brain.
Sensory memory holds a large amount of information but only for about a second. Paying attention to the content of sensory memory transfers incoming information to working memory, and information that is not transferred is quickly lost and cannot be retrieved, just as lights fade and sounds die away.
Working memory has a limited capacity. Most people can remember around seven items (or more precisely 7 +/- 2) by verbally rehearsing them.
Active rehearsal (muttering a phone number to yourself, or keeping two numbers in mind so as to add them together) keeps information in working memory, and we can increase the amount remembered by chunking the material using information in long-term memory to recode it into larger, meaningful units, so the limit may be seven letters, seven words, or seven lines of a song (the so-called ‘magical number seven’).
The process by which memories are encoded into long-term memory and stabilized, consolidation, happens in two ways. Synaptic consolidation, effected in hippocampal regions of the brain, occurs within the first few hours of learning and systemic consolidation involves transfer of information to the cortex, and occurs over a period of time varying between weeks and years.
Learning and memory, like the perceptual system, are active systems that employ organizing principles.
Information stays in the mind more easily if, for example, it is relevant, distinctive in some way, has been elaborated upon or worked with, and processed meaningfully as opposed to superficially.
Organizing information we want to remember confers an advantage when it comes to remembering it (thinking of ‘picnic food’, or ‘school lunches’ as you walk round the supermarket).
Some general principles of organization have been discovered, but at the same time each of us develops a personal organizational system based on past experience.
So we encode or organize incoming information differently, and have different priorities or interests when retrieving it. This helps us to adapt in the present: to avoid situations that trouble us and to seek out the kind of work that feels satisfying.
But it also means that our memories are not just ‘snapshots’ of the past. Just as we saw that perceiving and attending to the outside world involves constructing a view of reality, so we now see that learning and memory are also active, constructive processes. Furthermore, the accuracy of our memories may be irrelevant for many purposes.
In order to make the best use of what stays in the mind, it may be more important to remember meanings—and to use these as we think, reason, and communicate—than to remember precisely what happened.
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