| What is memory? As with many concepts in psychology, people have an intuition about what memory is until they are asked to define it. When we try to define memory, and break it up into its components, this becomes a complicated question. We talk about memorizing phone numbers, remembering a smell, remembering the best route to school. We talk about ‘‘knowing’’ that we’re allergic to ragweed or that we had a haircut three weeks ago. Is this knowing a form of memory? … What do all these forms of memory and knowledge have in common? How do they differ? … Psychologists tend to make conceptual distinctions among different types of memory. When we talk about different types of memory, an immediate question that comes to mind is whether these different types are conceptual conveniences, or whether they have an underlying neural basis. There is strong neurological evidence that particular memory systems are indeed localized in separate parts of the brain. The hippocampus and prefrontal cortex, for example, are known to play a role in the encoding and storage of particular forms of memory. However, the computational environment of the brain is massively parallel and widely distributed. It is likely that a number of processes related to memory are located throughout the brain. Further, some of the conceptual labels for memory systems, such as ‘‘procedural memory,’’ actually encompass somewhat independent processes that are conveniently categorized together (for pedagogical reasons), but do not necessarily activate a single distinct brain structure. … One kind of memory is the immediate sensory memory we experience as image persistence. For example, if you look outside the window on a bright day and then close your eyes, an afterimage stays on your retina for a few moments. This has been called iconic memory by Ulric Neisser. We talk about the auditory equivalent of this as echoic memory : for a few moments after hearing a sound (such as a friend’s voice) we are usually able to ‘‘hear’’ a trace of that sound in our mind’s ear. Richard Atkinson and Richard Shiffrin referred to these immediate sensory memories as being held in a sensory buffer. When you are holding a thought inside your head—such as what you are about to say next in a conversation, or as you’re doing some mental arithmetic—it stands to reason that this requires some type of short-term, or immediate, memory. This kind of memory, the contents of your present consciousness and awareness, has been called ‘‘working memory’’ by Alan Badelley, and is similar to what Atkinson and Shiffrin called short-term memory. Long-term memory is the kind of memory that most of us think of as memory—the ability to remember things that happened some time ago, or that we learned some time ago (usually more than a few minutes ago, and up to a lifetime ago). For example, you might have stored in long-term memory images from your high school graduation, the sound of a locomotive, the capital of Colorado, or the definition of the word ‘‘protractor.’’ (Actually, in the latter case, you might not be able to retrieve a definition of a protractor, but rather a visual image of what one looks like; this is also a form of long-term memory.) One of the important features of long-term memory is its durability. That is, we tend to think of long-term memories as staying with us for perhaps an indefinite period of time. We may not always be able to access them when we want (e.g., when you have somebody’s name on the tip of your tongue but can’t quite retrieve it), but we have the sense that the memories are ‘‘in there.’’ This is in contrast to short-term memories, which decay rapidly without rehearsal, and are not durable unless they somehow are transferred to long-term memory. The sensory memory/short-term memory/long-term memory distinction appears to have validity at the neural level. Psychologists also talk about different types of long-term memory, but it is not clear that these reflect different neural systems. Rather, they are different kinds of knowledge stored in long-term memory. It can be useful to make these distinctions for conceptual purposes. The psychologist Endel Tulving makes a distinction between episodic and semantic memory. There is something different between remembering your eighth birthday and remembering the capital of Colorado. Your eighth birthday is an episode that you can remember, one that occupied a specific time and place. There was also a time and place when you first learned the capital of Colorado, but if you’re like most people, you can’t remember when you learned it, only the fact itself. Similarly, we remember what words mean, but usually not when and where the learning occurred. This is called semantic memory. Remembering how to ride a bicycle or tie your shoe is an example of another type of memory called procedural memory. It is also important to make a distinction between memory storage (or encoding) and memory retrieval. One of the tricky parts about designing memory experiments is distinguishing between these operations. That is, if a subject cannot recall something, we need to distinguish between an encoding failure and a retrieval failure. Sometimes using different retrieval cues can bring up memories that seemed previously unreachable. Current memory researchers use a variety of different methods to study remembering, forgetting, storage, and retrieval processes. | — Daniel J. Levitin, Memory for Musical Attributes, Chapter 13 in Foundations of Cognitive Psychology - Core Readings, ed. Daniel J. Levitin | Indexes/24 |
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