Tj. Palmeri et Rm. Nosofsky, Central tendencies, extreme points, and prototype enhancement effects in ill-defined perceptual categorization, Q J EXP P-A, 54(1), 2001, pp. 197-235
Citations number
84
Categorie Soggetti
Psycology
Journal title
QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY SECTION A-HUMAN EXPERIMENTAL PSYCHOLOGY
In three perceptual classification experiments involving ill-defined catego
ry structures, extreme prototype enhancement effects were observed in which
prototypes were classified more accurately than other category instances.
Such empirical findings can prove theoretically challenging to exemplar-bas
ed models of categorization if prototypes are psychological central tendenc
ies of category instances. We found instead that category prototypes were s
ometimes better characterized as psychological extreme points relative to c
ontrast categories. Extending a classic and widely cited study (Posner & Ke
ele, 1968), participants learned categories created from distortions of dot
patterns arranged in familiar shapes. Participants then made pairwise simi
larity judgements of the patterns. Multidimensional scaling (MDS) analyses
of the similarity data revealed the prototypes to be psychological extreme
points, not central tendencies. Evidence for extreme point representations
was also found for novel prototype patterns displaying a symmetry structure
and for prototypes of grid patterns used in recent studies by McLaren and
colleagues (McLaren, Bennet, Guttman-Nahir, Kim, & Mackintosh, 1995). When
used in combination with the derived MDS solutions, an exemplar-based model
of categorization, the Generalized Context Model (Nosofsky, 1986), provide
d good fits to the observed categorization data in all three experiments.