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Abstract:
Abstract: Although many studies provide evidence for an
abstract number sense in nonhuman animals, human infants, and
adults, judgments of numerosity are highly influenced by sensory
properties of the stimulus (e.g. regularity in a visual array, or
frequency in an auditory sequence). Are these non-numerical
properties used as cues in the formation of an abstract
representation of magnitude, or are they themselves the bases of
supposed `numerosity' judgments? In the latter case, comparing
magnitude representations across modes of presentation should cause
large performance deficits. We assessed adults' ability to make
relative numerosity judgments about visual and auditory sets,
successively presented in either unimodal or crossmodal pairs. We
found no cost for crossmodal compared to unimodal comparisons, and
no cost for comparing numerosities across spatial and temporal
sets. These findings suggest that non-numerical stimulus properties
are used as preliminary cues in the formation of a quantity
representation that is independent of the modality or format of the
stimulus. Further, we found that reaction time and accuracy depend
only on the ratio of the compared numerosities, not on absolute set
size. These findings provide evidence that representations of
approximate numerosity are achieved through the non-iterative
transformation of modality-specific stimulus properties rather than
by any iterative process such as nonverbal counting (Gallistel
& Gelman, 1992).
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