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Language and Cognition Lab
An EEG research study on how the brain processes numbers.
Research on numerical cognition with infants, children, adults, cross-cultural studies and animal studies converge on the conclusion that there are two distinct systems for the perception of numerical quantity: A small-number system (1~3) invoking parallel individuation, or “subitizing”, and a large-number system (4+) that is based on Weberian magnitude estimation. The present study employed high density EEG to investigate the neural basis of differentiation between small-number (1~3), and large-number (4~6) perception. During EEG data collection, participants were presented with dot pattern stimuli containing 1 to 6 dots of varying size. They were instructed to press a key when they detected a change in the number of dots presented and were rewarded for correctly detecting changes. ERP analyses were conducted over the left and right occipital-temporal-parietal junction. For the early ERP component (N1; 160~180 ms), we observed that there was separation of ERPs within the subitizing range (1~3) but not beyond (4~6). A second later positivity (P3) was found in Cz and neighboring electrodes, that was associated with change detection. Numerical changes were categorized as “within small” (1~2, 2~1, 2~3, 3~2), “within large” (4~5,5~4,5~6,6~5). Changes that crossed the small to large boundary were labeled “small-to-large” and “large-to- small”. The P3 was observed for all change categories except for “within large.” These data, taken together, suggest a neural basis for the differentiation of small vs. large number perception at early stages of processing, and a later stage that involves more semantic numerical processing that is employed in change detection task.
Principal Investigator: Peter Gordon
Research Assistants: Sungbong Kim, Mary Llenell Paz, Erin (Reddick) Kirby, Michael Small, Jean Tang