Are faces “special”?

1. Are faces “special”? • Kanwisher • There are distinct brain regions (and processes within these regions) that are unique to processing face stimuli. • Gauthier & Tarr • There are unique subordinate-level categorization processes performed by “face areas.” These processes can also be applied to other types of stimuli (after a certain level of expertise).

2. Expertise hypothesis: other object categories can be “special” • Faces are not any different from any other object category. • All appearances of “special-ness” are a result of a lifetime of experience categorizing individual faces. • With sub-ordinate level discrimination training, other object categories can become special.

3. Levels of Categorization • “Basic” or “Category” or “Entry” Level • Car, Bird, Dog, Chair, etc… • “Subordinate” or “Individual” • “Hummer”, “Robin”, “Rocking chair”, etc… • Faces are automatically categorized at the Individual Level • Expertise Hypothesis: If we can train another class of objects to “skip” the basic level and automatically be recognized at the individual level, we should see the same kinds of brain activations, behaviors, etc. as we see for faces.

4. How is the brain organized? • Around “domain-specific” modules • OR • Around “domain-general” processes • For visual information: • “Geometry” maps vs. “Process” maps

5. Domain-specific processing Theoretical dis/advantages Empirical evidence Domain-general processing Theoretical dis/advantages Empirical evidence Empirical & Theoretical Question

6. Empirical evidence • Behavior • “Holistic” or “configural” processing • Inversion affects recognition memory more for faces than other objects. • Specific features (e.g., nose) are remembered more accurately when tested in the whole face than tested in isolation.

7. Empirical evidence • Prosopagnosia • A specific face processing deficit often due to brain injury but can be present from birth (congenital prosop.). • Object recognition is sometimes impaired but sometimes spared.

8. Empirical evidence • Electrophysiology • Face cells in monkeys. • Neurons that respond to faces and nothing else. • Lots of very new, recently published data. • ERP/MEG markers of face processing • N170

9. Empirical evidence • fMRI • Fusiform Face Area “FFA”

10. Empirical evidence • fMRI • Fusiform Face Area “FFA”

11. Domain-specific processing Theoretical dis/advantages Empirical evidence Domain-general processing Theoretical dis/advantages Empirical evidence Empirical & Theoretical Question

12. Levels of Categorization • “Basic” or “Category” or “Entry” Level • Car, Bird, Dog, Chair, etc… • “Subordinate” or “Individual” • “Hummer”, “Robin”, “Rocking chair”, etc… • Faces are automatically categorized at the Individual Level • Expertise Hypothesis: If we can train another class of objects to “skip” the basic level and automatically be recognized at the individual level, we should see the same kinds of brain activations, behaviors, etc. as we see for faces.

14. Theory: Does the brain have “modules” dedicated to a single type of information (e.g., faces)? • Data: fMRI responses in the FFA. • The interpretation of these data depends on your theoretical point of view.

15. fMRI FFA responses • Large responses to faces  “see, all it does is process faces” • Small, but statistically significant responses to nonfaces  “see, it processes other information in addition to faces”