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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). [12]
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. 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). [13]
Mental categories are sometimes referred to as schemas—patterns of knowledge in long-term
memory that help us organize information. 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).
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) [14] and then try to write down everything you can remember.