Eb. Lynch et al., Tall is typical: Central tendency, ideal dimensions, and graded category structure among tree experts and novices, MEM COGNIT, 28(1), 2000, pp. 41-50
Many accounts of categorization equate goodness-of-example with central ten
dency for common taxonomic categories; the best examples of a category are
average members--those that are most similar to most other category members
. In the present study, we asked 24 tree experts and 20 novices to rate goo
dness-of-example for a sample of 48 trees and found (1) that the internal s
tructure of the category tree differed between novices and experts and (2)
that central tendency did not determine goodness-of-example ratings for eit
her group. For novices, familiarity determined goodness-of-example ratings.
For experts, the "ideal" dimensions of height and weediness, rather than a
verage similarity to other trees, were the primary predictors of goodness-o
f-example ratings for experts. The best examples of tree were not species o
f average height, but of extreme height. The worst examples were the weedie
st trees. We also found systematic differences in predictors of goodness-of
-example as a function of type of expertise. We argue that the internal str
ucture of taxonomic categories can be shaped by goal-related experience and
is not necessarily a reflection of the attributional structure of the envi
ronment. Implications for models of category structure and category learnin
g are discussed.