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Abstract:
It is well known that the ability to discriminate between two
numbers improves as the numerical distance between them increases.
Measuring visual ERPs, Dehaene (1996) has shown that this distance
effect is reflected in the P2, with larger amplitudes for numbers
closer to each other. We were interested in examining whether these
results hold true for auditory stimuli. We recorded ERPs from 16
adults at 26 electrodes with an averaged reference. Stimuli were
presented via headphones as spoken words. In the number comparison
condition, subjects indicated by buttonpress whether numbers
(1,4,6,9) were larger or smaller than 5. In the control condition,
subjects listened to the same numbers without responding. For both
the number comparison and control listening conditions, N1/P2
showed the same classic morphology elicited by auditory stimuli.
Behavioral results from the comparison condition were consistent
with the literature. In contrast to the finding with visual
stimuli, the P2 in our comparison task did not show a distance
effect. However, preliminary P3 analyses showed clear-cut
differences. Larger amplitudes and shorter latencies were obtained
for larger numerical distances. This raises the question of whether
different processes underlie auditory versus visual number
comparisons as reflected by our effects observed at the P3 but not
at the P2. This work was supported by a grant from the McDonnell
Foundation.
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