In the previous three sections, authors explored the ways in which we sense information, classify it, and represent it in the mind. But once processed, where does that information go? In this section we will explore the issue as we examine the ultimate destination of information—the human memory.
For cognitive scientists, the study of memory involves three critical components: determining the structure of memory, understanding the ways in which information is acquired and stored in memory, and discovering the strategies by which information is retrieved from memory. Here I will highlight some of the most central discoveries from this ambitious agenda.
Those studying the structure of memory have identified two types of operating systems: short-term or working memory, and long-term memory. 1 Neurophysicists such as Brenda Milner (1966) have actually charted the structural location of these units within the human brain. Other researchers have documented the very different functions and characteristics of each memory system. 2 According to cognitive scientists, short-term memory contains only that information with which the brain is currently engaged. It allows us to “juggle” several dimensions of experience, shifting our focus from one to another, yet keep each dimension available for ready use. As such, short-term memory is limited in size and can encompass only a small number of entries. (In a classic study of the issue, George Miller  proposed that the short-term memory can hold seven plus or minus two “chunks” of information—although the density of a chunk can vary significantly, encompassing a single word or a complex array of items.) Long-term memory, in contrast, brings longevity to thought; it represents the psychological past, housing all of the information that is acquired over a lifetime. As such, long-term memory is nearly limitless in its information capacity. It is established through a long evolutionary history, one characterized by uneven growth.
The structure of long-term memory can be further divided. Endel Tulving (1985; 1993), a leading scholar in this area, suggests that long-term memory consists of