Finger-digit compatibility in Arabic numeral processing

Finger-digit response compatibility was tested by asking participants to identify Arabic digits by pressing one of ten keys with all ten fingers. The direction of the finger-digit mapping was varied by manipulating the global direction of the hand-digit mapping as well as the direction of the finger-digit mapping within each hand (in each case, from small to large digits, or the reverse). The hypothesis of a left-to-right mental number line predicted that a complete left-to-right mapping should be easier whereas the hypothesis of a representation based on finger counting predicted that a counting-congruent mapping should be easier. The results show that a mapping congruent with the prototypical finger-counting strategy reported by the participants leads to better performance than a mapping congruent with a left-to-right oriented mental number line, and demonstrate that finger-counting strategies clearly influence the way numerical information is mentally represented and processed.