Embodied markedness of parity? Examining handedness effects on parity judgments.

Parity is important semantic information encoded by numbers. Interestingly, there are hand-based effects in parity judgment tasks: right-hand responses are faster for even and left-hand responses for odd numbers. As this effect was initially explained by the markedness of the words even vs. odd and right vs. left, it was denoted as the linguistic markedness of response codes (MARC) effect. In the present study, we investigated whether the MARC effect differs for right and left handers. We conducted a parity judgment task, in which right- and left-handed participants had to decide whether a presented single or two-digit number was odd or even by pressing a corresponding response key. We found that handedness modulated the MARC effect for unit digits. While we replicated a regular MARC effect for right handers, there was no evidence for a MARC effect for left handers. However, closer inspection revealed that the MARC effect in left handers depended on the degree of left-handedness with a reversed MARC effect for most left-handed participants. Furthermore, although parity of tens digits interfered with the processing of unit digits, the MARC effect for tens digits was not modulated by handedness. Our findings are discussed in the light of three different accounts for the MARC effect: the linguistic markedness account, the polarity correspondence principle, and the body-specificity hypothesis.