Memory

The multi-store model of memory developed by Richard Atkinson and Richard Shiffrin has guided research in memory and its development. The model is supported by extensive experimental evidence and is applied productively in work with individuals who have suffered brain injuries and students with typical learning characteristics as well as learning difficulties. In this information-processing model, illustrated in Figure 1, human memory is seen as operating in a manner analogous to that of a computer. The model depicts three separate memory stores that function as the hardware of the memory system: long-term memory, the sensory register, and working memory. Long-term memory, which is what people typically mean when they refer to memory, is a relatively permanent memory store with an apparently limitless capacity. It includes both semantic memory, a mental reference book that contains facts about the world, and episodic memory, a repository of stored traces of experienced events. It should be noted, however, that representations of learned material or personal experiences do not enter long-term memory directly. Information is moved through earlier stores to long-term memory.

Sights and sounds from the world enter the memory system through the sensory register. This store holds the icon of a visual display or the echo of a sound for a very brief period of time. Within only one second, information that an individual has not FIGURE 1 extracted from the icon or echo is lost. Hence, much of what enters the senses never becomes part of long-term memory. Information that is identified by individuals is often maintained in working memory while the individual interprets it, transforms it, or uses it to solve problems. Applying the computer metaphor, the contents of working memory correspond to open files and running programs. Information moves from working memory into long-term storage when it is processed in a way that makes it meaningful to the individual.

The long-term memory store is often incorrectly described as containing complete and actual representations of past events. In contrast, long-term memory is understood by psychologists to be a reconstructive process. Memories can be altered when individuals encounter new material that interferes with stored information or make inferences that are added to a representation. A well-documented way in which inference occurs is through the operation of schemas, which are organized sets of facts (for example, beliefs about what happens during a visit to the doctor). In a classic study conducted in 1932, Frederick Bartlett read English research participants a story that described events that were inconsistent with their own life experiences and hence seemed bizarre. When they were later asked to recall the story, the participants distorted the actions that took place in a manner that made them consistent with their own culture.

In addition to the memory stores described above, mental strategies are an important component of the information processing system. Strategies correspond to the software of the computer. They are learned procedures that individuals use to direct attention, move information from working to long-term memory, or apply techniques for solving problems. A second grader who repeats a telephone number before dialing it is using verbal rehearsal, a simple memory strategy; a ninth grader who learns a new vocabulary word by using it to describe a principle he has previously learned is using elaboration, an especially effective strategy. Strategies make it possible for memory to be intentional, the term applied when information is deliberately learned or purposefully retrieved. In contrast, memory is described as incidental when information is acquired in the process of performing another activity.

It should be apparent from even this brief introduction that the components of information processing are constantly interacting as a system. The contents of the long-term store are important in encoding, the process of taking information from the world into the memory system. Information stored in long-term memory makes it possible to identify the stimuli in the sensory register so that it can be moved to another store. Knowledge from long-term memory enables the application of strategies or problem-solving procedures in working memory. The contents of permanent memory also determine to a large extent how meaningful new material is, and hence how it can be organized and accessed from the long-term store.

The information-processing model is particularly useful in understanding explicit memory, the type of memory of greatest interest to parents and teachers. Explicit memories are potentially conscious and can be described verbally or pictured in images. A child uses explicit memory when she describes a class field trip or edits a report by applying grammatical rules she has learned. In contrast, some information may affect task performance without entering the individual's conscious awareness. In this case, it is described as implicit memory. Implicit memory is assessed by indirect measurements, such as determining how much quicker individuals can add letters to complete a word when they have previously been presented with a target word, or by physiological indicators, such as changes in galvanic skin response.

Understanding children's memory requires identifying the age-related changes that occur in the components of the information processing system. The first significant advance, of course, is the emergence of memory in development. In the next section, the point in life at which the memory system can be considered to be "up and running" will be discussed. The following sections will examine the changes that occur during childhood in the memory stores and in the use of strategies. The importance of these transitions in children's everyday lives will be explored in each section.