Chapter 9: Goldstone, R. L., Gerganov, A., Landry, D. & Roberts, M. E. Learning to see and conceive (pp. 163-188).

Interactive relationship between conception and perception:We construct concepts out of more elemental perceptual features: cars = wheels, bumpers, hoods, etc.We see perceptual signals as elemental features (we see wheels, bumpers, and hoods) because we have a concept of “car.” Degree of top-down influence on basic perception is often underestimated. Conceptual influences are “early” and strong

Top-down effects on early perceptual processing

• Evidence: • Neurological:• Enhanced electrical brain activity (assuming visual cortex, maybe

earlier) occurs 164ms after presentation of pattern in expert’s domain compared to novice.

• Expertise effects: Prolonged Practice effects producing subtle discriminatory pattern detection/recognition improvements (X ray detection; motion, sound, etc) associated with changes in primary visual cortex (visual) and even thalamic/cochlear level for auditory.

Top-down effects

• Brain changes due to expertise effects:• Fusiform face area: associated with face processing (pan human

universal expertise) but also other forms of expert pattern recognition (butterflies, chess boards, birds, dogs, etc.).

• Somatosensory cortex: numerous studies showing how expertise (tactile discrimination, violists, guitar players etc.) affects hand/finger representation.

Top-down influences

• Functional:• Familiar patterns more quickly

segregated into figure relative to unfamiliar patterns.

• Developmental:• Familiarized, though not

necessarily “natural” figures, are assumed to be unified patterns by infants.

Fam: Prefam:cir=38% cir=58%

Pm=61% Pm= 42%

Top down influences:Summary

• Authors summarize developmental findings thusly:

• “Taken together these results indicate that early in development children are predisposed to learn shapes from their environments and then interpret their environment in terms of these learned shapes” p. 167.

Learning to see and conceive: critical processes• Unitization: when elemental features become fused into a single pattern

due to prolonged practice in identifying them as a unit. • Goldstone (2000) study provides evidence that unitization can occur even

when using randomly combined features where an impossibly large total set of “units” is possible (details can be omitted).

• Differentiation: unified perceptual features can become segregated and processes separately with practice.

• Separable dimensions: two dimensions or stimulus features that can be attend to in isolation from each other. Size and brightness – people can make categorizations along one while completely ignoring the other (note: this is not always true for children!).

• Integral: processing along one dimension is influenced by changes on the other (saturation and brightness).

Expertise Effects• Evidence exists that some experts can separate

integral dimensions (artists can process saturation apart from brightness).

• Goldstone and Steyvers, 2001; another hopelessly complicated experiment provides evidence that integral dimensions might become separable with training. Conclusion is controversial – other research suggests that relative “weightings” of two dimensions can be altered but not true reparability.

Differentiate or unitize?

• Questions the visual system asks:• Do features (dimensions) represent different sources

of variability? Do they seem to vary independent of one another? If so, differentiate.

• Do features (dimensions) co-vary frequently? If so, unitize.