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Creating Objects and Object Categories for Studying Perception and Perceptual Learning
Published on: November 2, 2012
Basic-level categorization of intermediate complexity fragments reveals top-down effects of expertise in visual
Assaf Harel1, Shimon Ullman, Danny Harari
1Laboratory of Brain and Cognition, National Institute of Mental Health, Bethesda, MD 20892, USA. assaf.harel@nih.gov
Journal of Vision
|July 30, 2011
Summary
Visual expertise in object recognition is not just about specialized perceptual strategies. Experts show a general processing advantage, using top-down knowledge and attention to quickly distinguish categories like cars.
Area of Science:
- Cognitive Psychology
- Neuroscience
- Visual Perception
Background:
- Visual expertise is typically defined by superior performance within homogeneous categories.
- The manifestation of real-world expertise at basic-level categorization remains less understood.
- The interplay between stimulus-driven and top-down factors in expertise is a key research question.
Purpose of the Study:
- To investigate how real-world expertise influences basic-level object categorization.
- To determine the contribution of stimulus-driven (mutual information) and top-down (knowledge, attention) factors.
- To compare categorization performance of experts and novices across different object categories.
Main Methods:
- Car experts and novices categorized image fragments of cars, airplanes, and faces.
- Image fragments varied in mutual information (MI), a measure of feature diagnosticity.
- Response times (RT) and accuracy were recorded; response criteria were analyzed.
Main Results:
- Categorization of faces and airplanes was similar across groups, improving with higher MI.
- Novices were slower to categorize car fragments than faces/airplanes; experts were equally fast.
- Expert advantage in car categorization was consistent across MI levels; experts showed a bias toward car responses.
Conclusions:
- Expertise at the basic level involves more than specialized perceptual strategies.
- Expertise confers a general processing advantage, likely mediated by top-down mechanisms like knowledge and attention.
- These top-down mechanisms enhance an expert's ability to efficiently distinguish between object categories.
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