BEYOND CATEGORIES: Understanding the factors underlying category specificity in the brain

How can it be that some individuals with temporal lobe damage lose the ability to recognize biological objects such as fruits and vegetables yet retain the ability to recognize non-biological objects such as tools and furniture? Impairments can be highly selective, as in prosopagnosia, where individuals have disproportionate difficulty recognizing faces. Category-specific impairments raise intriguing questions about how information is processed and stored in the brain: How do brain regions become specialized for particular categories? How malleable are categorization processes and boundaries? What are the cortical dynamics of factors that influence categorization?

Brain imaging studies in neurologically typical individuals indicate rich categorical structure including specialization for faces, body parts, tools, and words. Although these data suggest that category representations are stable and discrete, other studies show evidence of neural plasticity with the acquisition of perceptual expertise (the ability to rapidly identify objects within a homogeneous category). My theoretical approach conceptualizes category specificity as an emergent property of a dynamic representational system that is widely distributed and overlapping. My approach offers an alternative framework to domain-specific accounts and pushes my research beyond defining category boundaries to examine general principles that underlie how category specificity emerges and changes over time and in different contexts. My research program uses both behavior and electrophysiology to investigate how factors such as experience, context, and task demands interact with object properties and brain processing biases to produce a variety of category-specific effects.

My work has uncovered general principles that explain a broad range of behavior. I have demonstrated that an inability to perceptually integrate multiple fine-level details in prosopagnosia affects both face and non-face recognition. Thus, face recognition deficits may be the most visible symptom of a general object recognition impairment. I have also demonstrated that holistic processing, a marker of face specificity, underlies expert perceptual discrimination in multiple domains, including cars, birds, alphabetic and non-alphabetic writing systems.

My larger research program addresses fundamental questions such as: 1) What can category specific effects tell us about brain-behavior relationships? 2) Why are biological categories vulnerable to brain damage? 3) How does experience impact categorization and generalization of expert skills? These questions are important to understand what types of training programs best facilitate expertise transfer, and to predict when skills will transfer. One extension of my research on categorization and limits of expertise transfer is to better understand and ameliorate racial bias and other race effects. The use of EEG/ERP methodology reveals the underlying cortical dynamics of these often unconscious processes.