Abstract
Directional response biases due to a conceptual link between space and number, such as a left-to-right hand bias for increasing numerical magnitude, are known as the SNARC (Spatial-Numerical Association of Response Codes) effect. We investigated how the SNARC effect for numerosities would be influenced by reading-writing direction, task instructions, and ambient visual environment in four literate populations exemplifying opposite reading-writing cultures—namely, Arabic (right-to-left script) and English (left-to-right script). Monoliterates and biliterates in Jordan and the U.S. completed a speeded numerosity comparison task to assess the directionality and magnitude of a SNARC effect in their numerosity processing. Monoliterates’ results replicated previously documented effects of reading-writing direction and task instructions: the SNARC effect found in left-to-right readers was weakened in right-to-left readers, and the left-to-right group exhibited a task-dependency effect (SNARC effect in the smaller condition, reverse SNARC effect in the larger condition). Biliterates’ results did not show a clear effect of environment; instead, both biliterate groups resembled English monoliterates in showing a left-to-right, task-dependent SNARC effect, albeit weaker than English monoliterates’. The absence of significant biases in all Arabic-reading groups (biliterates and Arabic monoliterates) points to a potential conflict between distinct spatial-numerical mapping codes. This view is explained in terms of the proposed Multiple Competing Codes Theory (MCCT), which posits three distinct spatial-numerical mapping codes (innate, cardinal, ordinal) during numerical processing—each involved at varying levels depending on individual and task factors.
Highlights
The results reported below concern the central analysis of differences in response times (RTs) by group, pair size, and condition, as well as additional models of RT differences that
Our first set of analyses focused on RT differences from the test blocks and excluded RTs that were for incorrect responses, less than 150 ms, or outliers more than 3 SD from individual participant means (= 3.2% of the data)
It was important to follow the same overall design in [26] to facilitate cross-comparison between studies and establish whether SNARC effects occur in bidirectional biliterates to begin with, that the current findings have laid this groundwork, it would be advantageous to extend this research to more numerosities outside the subitizing range in order to see whether the groups examined in this study show stronger SNARC effects with these larger numerosities [84,85,86]
Summary
Humans develop the ability to quantify object sets (“numerosities”) early in life, and the early conceptualization of numerosities is thought to form the basis for knowledge of symbolic numbers (e.g., 7, seven) [1,2,3,4] (cf [5] for an alternative view). Cultural factors weaken but do not reverse left-to-right spatial biases in numerosity processing. Civilizations (http://www.bu.edu/smscinst/) and from the Jordanian-American Fulbright Commission (https://www.fulbright-jordan.org/) to D.L. as well as a BU Peter Paul Career Development Professorship (https://www.bu.edu/ provost/awards-publications/award-opportunities/ career-development-professorships/) to C.B.C. Funding for publication was received from the Boston University Center for the Humanities (http:// www.bu.edu/humanities/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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