Central tendencies, extreme points, and prototype enhancement effects in ill-defined perceptual categorization

Citation
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
ISSN journal
02724987 → ACNP
Volume
54
Issue
1
Year of publication
2001
Pages
197 - 235
Database
ISI
SICI code
0272-4987(200102)54:1<197:CTEPAP>2.0.ZU;2-P
Abstract
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.