Monday, June 18, 2012

Barsalou: "The instability of graded structure" (1987)

Lawrence Barsalou summarizes the findings from a large number of categorization experiments performed by him and his colleagues 1980-86. The upshot is that prototypicality effects are highly unreliable and context-sensitive.

The Instability of Prototype Effects

Barsalou describes the following types of variability between judgments of prototypicality:
  1. Pages 108-109: Contrary to what Rosch claims, the between-subject reliability of similarity judgments is generally low, with an average correlation of around 50%. Rosch (1975) and Armstrong, Gleitman, and Gleitman (1983) only achieve their 90% correlation coefficients by comparing group averages rather than individuals.
  2. Pages 109-111: People differ in their similarity judgments -- students, for instance, differ from professors. Yet, people are surprisingly good at simulating the similarity estimates of other people when asked to make similarity judgments from their point of view.
  3. Pages 111-112: People are not very stable in their judgments. Their self-correlation is about 92% after one hour, 87% after one day, and around 80% after one week or more.
I would imagine that the task about "taking the point of view" of someone else is highly sensitive to tiny details in the test materials. Barsalou does not discuss the methodology in detail, but I can see that the 1984 research report that describes the experiment is available at his website.

The Alternative Theory

In order to fix the theoretical problems that result from this instability of prototype effects, Barsalou suggests that concepts should be seen as "temporary constructs in working memory that are tailored to current situations" (p. 120). This does indeed allow for a more anarchistic type of conceptual system, but it is also a very weak theory (i.e., it is consistent with almost all types of behavior).

My suspicion is here -- as often when "representations" start to disintegrate into a disorderly pile of highly unstructured improvisations -- that the whole set-up somehow captures the wrong phenomenon. This can be true both of wild cognition (how do you decide, in conversation, whether or not to call something, say, a tool?) and in the experimental situation (how do subjects construe the questions they get, and what do they think that the experimenter wants them to do?).

The context-sensitivity seems, I think, to suggest that categorization is a fairly "high-level" type of cognition, in spite of the claims of Rosch and others. People might just use quite intelligent, deliberate, and context-sensitive strategies for picking words, finding or ignoring similarities, and the like. But I realize this is pretty weak, too.

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