Numerical cognition is essential to many aspects of life and arithmetic abilities predict academic achievements better than reading. Acquiring a solid sense of numbers and being able to mentally manipulate numbers are at the heart of this ability. In recent years research has been marked by looking for the underlying mental operations, an effort to unravel the neural tissue that supports these operations, and identifying low-level deficits that underlie deficiencies in numerical cognition such as developmental dyscalculia. This accumulated body of results led to a widely accepted view of an innate, domain-specific, core numerical knowledge based on the ability to perceive and manipulate discrete quantities.
However, several findings suggest that this wide agreement needs to be examined carefully; 1) similar to their sensitivity to discrete quantities (e.g. enumeration of objects), infants show sensitivity to non-countable continuous dimensions like perception of area (Brannon, 2006) and size (Lourenco, 2010). Mix et al. (2002) surveyed the literature on quantification in infancy and early childhood and suggested that the literature provides no clear-cut evidence that infants use numbers to perform quantitative tasks and that there is evidence that infants respond to amount of substance, rather than discrete numbers, in what had seemed to be numerical tasks. 2) Developmental trajectories similar to those with numbers have been shown to rely on domain-general rather than domain-specific abilities (Holloway, 2008). During development, language may provide a medium that bridges between core domain-specific systems (Munkholm, 2001; Platt, 2009; Spelke, 2003). Lastly, 3) numbers are intimately associated with non-countable dimensions (e.g. area, brightness). Accordingly, the current proposal examines the possibility that there exists an evolutionarily older system dedicated to the perception and evaluation of non-countable dimensions (e.g. sizes or amounts).
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