Memories that are stored in LTM are not isolated but rather are linked together into categories—networks of associated memories that have features in common with each other. Forming categories, and using categories to guide behavior, is a fundamental part of human nature. Associated concepts within a category are connected through spreading activation, which occurs when activating one element of a category activates other associated elements. For instance, because tools are associated in a category, reminding people of the word “screwdriver” will help them remember the word “wrench.” And, when people have learned lists of words that come from different categories (e.g., as in the Retrieval Demonstration), they do not recall the information haphazardly. If they have just remembered the word “wrench,” they are more likely to remember the word “screwdriver” next than they are to remember the word “dahlia,” because the words are organized in memory by category and because “dahlia” is activated by spreading activation from “wrench” (Srull & Wyer, 1989).
Some categories have defining features that must be true of all members of the category. For instance, all members of the category “triangles” have three sides, and all members of the category “birds” lay eggs. But most categories are not so well-defined; the members of the category share some common features, but it is impossible to define which are or are not members of the category. For instance, there is no clear definition of the category “tool.” Some examples of the category, such as a hammer and a wrench, are clearly and easily identified as category members, whereas other members are not so obvious. Is an ironing board a tool? What about a car?
Members of categories (even those with defining features) can be compared to the category prototype, which is the member of the category that is most average or typical of the category (see Figure \(\PageIndex{1}\)). Some category members are more prototypical of, or similar to, the category than others. For instance, some category members (robins and sparrows) are highly prototypical of the category “birds,” whereas other category members (penguins and ostriches) are less prototypical. We retrieve information that is prototypical of a category faster than we retrieve information that is less prototypical (Rosch, 1975).
Figure \(\PageIndex{1}\): Prototypicality. Category members vary in terms of their prototypicality. Some cats are “better” members of the category than are others. [Clockwise from top left: “Lion - Linton Zoo” by Airwolfhound is licensed under CC BY-SA 2.0; “Sasha” by Kimli is licensed under CC BY-NC 2.0; “Sphinx” by Wei-Hang Chua is licensed under CC BY-NC-ND 2.0; “Beauty : Bon lundi et bonne semaine à tous!” by julicath/Cath is licensed under CC BY-NC-ND 2.0.]
Mental categories are sometimes referred to as schemas— patterns of knowledge in long-term memory that help us organize information (see Figure \(\PageIndex{2}\)). We have schemas about objects (that a triangle has three sides and may take on different angles), about people (that Sam is friendly, likes to golf, and always wears sandals), about events (the particular steps involved in ordering a meal at a restaurant), and about social groups (we call these group schemas stereotypes).
Figure \(\PageIndex{2}\): Different schemas. Our schemas about people, couples, and events help us organize and remember information. [“smiling in Barcelona” by Gene Krasko is licensed under CC BY-NC-ND 2.0; “Couple” by David Shen is licensed under CC BY 2.0; “Lynne & Jérémie” by Shawn Harquail is licensed under CC BY-NC 2.0.]
Schemas are important in part because they help us remember new information by providing an organizational structure for it. Read the following paragraph (Bransford & Johnson, 1972) and then try to write down everything you can remember.
The procedure is actually quite simple. First you arrange things into different groups. Of course, one pile may be sufficient depending on how much there is to do. If you have to go some- where else due to lack of facilities, that is the next step; otherwise you are pretty well set. It is important not to overdo things. That is, it is better to do too few things at once than too many. In the short run this may not seem important, but complications can easily arise. A mistake can be expensive as well. At first the whole procedure will seem complicated. Soon, however, it will become just another facet of life. It is difficult to foresee any end to the necessity for this task in the immediate future, but then one never can tell. After the procedure is completed, one arranges the materials into different groups again. Then they can be put into their appropriate places. Eventually they will be used once more and the whole cycle will then have to be repeated. However, that is part of life.
It turns out that people’s memory for this information is quite poor, unless they have been told ahead of time that the information describes “doing the laundry,” in which case their memory for the material is much better. This demonstration of the role of schemas in memory shows how our existing knowledge can help us organize new information, and how this organization can improve encoding, storage, and retrieval.
