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Abstract:
Abstract: The ability to discriminate quantities (e.g., "a
lot" vs. "a few") is thought to be related to an understanding of
numerical magnitude, but it has not been established whether these
two operations share some of the same neural processes. Previously,
we have demonstrated that numeral comparisons showed a "distance
effect" on P3 amplitude and latency, while earlier components (N1,
P2) were unaffected. In this study, we examined the effects of
quantity comparison on the N1, P2 and P3 components. ERPs were
recorded from 15 adults at 26 electrodes with an averaged
reference. Stimuli consisted of arrays (1,3,7 or 9) of dots
presented on a monitor. Subjects indicated by buttonpress whether
the dot array represented a small (1, 3) or large (7, 9) quantity.
In contrast to the numeral comparison task, this quantity
comparison task did not show the previously observed effects on the
P3. However, at the T6 electrode, P2 amplitude for "a few" (1, 3)
dots was significantly smaller than for "a lot" (7, 9). This is
consistent with Dehaene's proposal that quantity processing is
reflected in a right-hemisphere P2 component. Our finding suggests
that the comparison of quantity and number are subsumed by
different cognitive systems; quantity comparison seems to be an
earlier, and possibly more basic process. This work was supported
by the McDonnell Foundation.
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