The effect of orientation on number word processing

Besner and Coltheart [Besner, D., & Coltheart, M. (1979). Ideographic and alphabetic processing in skilled reading of English. Neuropsychologia, 17, 467–472] found a size congruity effect for Arabic numbers but not for number words. They proposed that Arabic numbers and number words are processed in different ways. However, in their study orientation of the stimuli and notation were confounded. In the present study, it is found that orientation of number words affects numerical processing. Orientation modulates both the size congruity effect and the distance effect; horizontal presentation produces similar results to those produced by Arabic numbers whereas vertical orientation produces different results. Accordingly, it is proposed that our cognitive system is endowed with two different mechanisms for numerical processing; one relies on a visual-spatial code and the other on a verbal code.