cambridge | In this review, we are pitting two theories against each other: the more
accepted theory—the ‘number sense’ theory—suggesting that a sense of
number is innate and non-symbolic numerosity is being processed
independently of continuous magnitudes (e.g., size, area, density); and
the newly emerging theory suggesting that (1) both numerosities and
continuous magnitudes are processed holistically when comparing
numerosities, and (2) a sense of number might not be innate. In the
first part of this review, we discuss the ‘number sense’ theory. Against
this background, we demonstrate how the natural correlation between
numerosities and continuous magnitudes makes it nearly impossible to
study non-symbolic numerosity processing in isolation from continuous
magnitudes, and therefore the results of behavioral and imaging studies
with infants, adults and animals can be explained, at least in part, by
relying on continuous magnitudes. In the second part, we explain the
‘sense of magnitude’ theory and review studies that directly demonstrate
that continuous magnitudes are more automatic and basic than
numerosities. Finally, we present outstanding questions. Our conclusion
is that there is not enough convincing evidence to support the number
sense theory anymore. Therefore, we encourage researchers not to assume
that number sense is simply innate, but to put this hypothesis to the
test, and to consider if such an assumption is even testable in light of
the correlation of numerosity and continuous magnitudes.
