Learning and Contemporary Views Memory

People have long wondered how best to characterize learning and memory. Most people typically conceive of memory as a place in which information is stored. As Henry Roediger has noted, this spatial metaphor has dominated the study of memory: "We speak of storing memories, of searching for and locating them. We organize our thoughts; we look for memories that have been lost, and if we are fortunate, we find them" (1980, p. 232). Aristotle compared memory to a wax tablet, Plato invoked the image of an aviary, and St. Augustine of Hippo suggested similarities to a cave. Increasingly, the metaphors involved the most recent or most impressive technological accomplishment, as with René Descartes and his analogy to the water-powered automata in the French royal gardens and later by comparisons to the gramophone (an updating of the wax-tablet metaphor) and then a telephone exchange.

The so-called "cognitive revolution" that began in the mid-1950s ushered in the information-processing approach to the study of learning and memory. The main metaphor became the computer; people were seen as general-purpose processors of information capable of manipulating internal representations. As with computers, there was an emphasis on the interaction between hardware and software, usually relabeled structure and process, respectively. By the end of the 1960s, the standard view of memory was the modal model (after the statistical term mode) with its set of stores, registers, and buffers. Structuralist views continue to use the spatial metaphor and emphasize a memory system in which information is stored. According to these accounts, the store in which a memory resides determines the mnemonic properties.

An alternative to the structural approach is the proceduralist approach, which views memory not so much as a thing that is stored but rather as the result of a process. As David Wechsler put it, "Memories are not like filed letters stored in cabinets.… Rather, they are like melodies realized by striking the keys on a piano" (p. 151). The melodies are a byproduct of pressing keys just as memory is a by-product of processing information. According to this account, the processing performed at encoding and retrieval determines the mnemonic properties.

Consider the essential difference between these two accounts. Within the modal model of the 1960s and early 1970s there were three memory structures: a sensory register, short-term memory (STM), and long-term memory (LTM). Information is first briefly registered in the appropriate sensory buffer, visual information in iconic memory, auditory information in echoic memory, and so on. These buffers hold raw physical information in an unanalyzed form for a very short period of time, perhaps 250 milliseconds. Additional processing is required to convert the information from its sensory form to a more durable representation that is held by short-term memory. Short-term memory serves mainly as a buffer in which information can be temporarily stored and has a limited capacity, usually given as 7 plus or minus 2 items. Items in short-term memory decay over time unless rehearsed; rehearsal is also the way in which information gets copied into long-term memory. Long-term memory is the main memory system and stores all knowledge. It has no known capacity limitations. Whereas information loss from short-term memory is thought to be permanent, it is unclear whether there is permanent loss from LTM.

Table 1 summarizes the essential points from the structuralist point of view. When an item is in STM, it will be stored using an acoustic code (how the word sounds), the capacity will be limited to 7 plus or minus 2 items, and the items will decay within about twenty seconds. In contrast, when an item is in LTM, it will be stored using a semantic code (what the word means), the capacity will be (almost) unlimited, and the item may very well never be forgotten.

A proceduralist would agree with almost everything the structuralist has proposed, except that the proceduralist would ask the following question: What does the top row in the table add to our understanding? In other words, we could delete the top row and still have a complete and accurate description of memory. When words are processed based on how they sound, there will be a very small capacity and the information will not be available for very long. When words are processed based on what they mean, however, there will be an enormous capacity, and the information will be available for a long time.

The divergence between the structuralist and proceduralist approaches has grown since the 1970s. One current debate concerns whether memory is best characterized as a set of

independent systems—a continuation of the spatial metaphor—or as a set of interrelated processes (see, for example, Foster and Jelicic). This more modern structuralist approach has greatly changed the modal model and generally names five different memory systems. The proceduralist approach has refined the idea of memory as a by-product of processing to focus on the relationship between the processing performed at encoding and the processing performed at retrieval.