Academic journal article Memory & Cognition

Subtyping as a Knowledge Preservation Strategy in Category Learning

Academic journal article Memory & Cognition

Subtyping as a Knowledge Preservation Strategy in Category Learning

Article excerpt

Subtyping occurs when atypical examples are excluded from consideration in judging a category. In three experiments, we investigated whether subtyping can influence category learning. In each experiment, participants learned about a category where most, but not all, of the exemplars corresponded to a theme. The category structure included a subtyping dimension, which had one value for theme-congruent exemplars and another for exception exemplars. On the basis of work by Hayes, Foster, and Gadd (2003) and studies on social stereotyping, we hypothesized that this subtyping dimension would enable the participants to discount the exception exemplars, thereby facilitating category learning. Contrary to expectations, we did not find a subtyping effect with traditional category-learning procedures. By introducing the theme prior to learning, however, we observed increased effects on typicality ratings (Experiment 1) and facilitated learning of the category (Experiment 2). Experiment 3 provided direct evidence that introducing the theme prior to learning enhanced the subtyping effect and provided support for a knowledge-gating explanation of subtyping. We conclude that subtyping effects are strongest on already-learned concepts and that subtyping is unlikely to aid in the learning of new concepts, except in particular circumstances.

Learning a new concept is greatly facilitated when prior knowledge can be brought to bear on it (see, e.g., Heit & Bott, 2000; Kaplan & Murphy, 2000; Murphy & Allopenna, 1994; Rehder & Murphy, 2003). One problem with knowledge, however, is that it is sometimes wrong. Even when it is not wrong, it is often rather shallow, not explaining phenomena in very great detail (Keil & Wilson, 2000; Rozenblit & Keil, 2002). One might wonder, then, how real-world knowledge can manage to help us learn anything new. If we have a belief about why birds fly, having to do with wings, then how do we explain turkeys or penguins, which have wings but do not fly? And if we cannot, in fact, make such predictions on the basis of our knowledge, is it any use at all?

Fortunately, research has shown that even if one's prior knowledge does not relate all the features in the concept, it still aids in the learning of the concept (Kaplan & Murphy, 2000). Furthermore, if some of the knowledge is wrong in individual cases, the knowledge still helps people learn, so long as it is generally correct (Murphy & Kaplan, 2000). So, however knowledge influences concept acquisition, it does not require unrealistic levels of perfection to be helpful. The occasional turkey does not prevent us from understanding how birds usually fly and from using that knowledge to learn about new flying animals.

There are other ways in which knowledge may persist even when it is not completely correct. Researchers concerned with social stereotypes have examined how it is that stereotypes can persist in the face of disconfirming group members. As a general rule, people are very reluetant to change their views about social categories, even when there is abundant evidence contradicting them (see Hilton & von Hippel, 1996, for a review). For example, Stephan ( 1985) demonstrated that negative stereotypes continued to be maintained even after long periods of cooperation with members of the stereotyped group. One of the strategies used to maintain these beliefs in the face of disconfirming information is known as subtyping (e.g., Hewstone & Hamberger, 2000; Hewstone, Hassebrauck, Wirth, & Waenke, 2000; Kunda & Oleson, 1995). Subtyping is the process by which group members who disconfirm the stereotype are clustered together to form a subgroup. By segregating such members, the remaining group members can be interpreted as the "real" group, which does, in fact, maintain the stereotype.

The effect of subtyping is to reduce the belief change necessitated by disconfirming examples, as measured by ratings of the stereotypical belief. …

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