Rapid communication The mental number line dominates alternative, explicit coding of number magnitude.

ABSTRACT

Numerical judgments are facilitated for left-space responses to a smaller number and right-space responses to a larger number (the spatial-numerical association of response codes, SNARC, effect). Despite support for a mental number line (i.e., spatial) explanation of the SNARC effect, this account has been challenged by an intermediate-coding theory that makes use of a polarity-correspondence principle. The latter is a general explanatory framework whereby stimulus and response dimensions are represented in a categorical, binary manner, with complementary categories coded as having either positive or negative polarity. When stimulus and response polarity match, responding is facilitated. In the present experiment we pitted explicitly presented close-far coding against an implicit mental number line (i.e., left-right coding). Subjects categorized numbers (1, 4, 6, and 9) as greater or less than a standard (5) using keys defined only as close to and far from a starting key. We found that, despite instructing subjects to use a close-far coding scheme, they exhibited a typical SNARC effect, with small-number responses facilitated on the left and large-number responses on the right. These results are discussed in the context of results supporting the polarity explanation and with respect to representational pluralism.