Fractions can be processed using a global approach, when we extract the numerical value, a componential ap- proach, when we focus on the numerator and/or denomina- tor, or with both approaches. We investigated how the left (LH) and the right (RH) hemispheres deal with these differ- ent approaches. We used a priming paradigm where both the prime and the target were fractions. There were four prime- target relations: fractions with Same Numerator (SN), Same Denominator (SD), Multiplicative (MULT) and Unrelated (UNR). The prime appeared centrally, while the target ap- peared in the left (RH), or in the right visual field (LH). The task was to compare the target with the fraction 1/2, or the number 1. When the target was compared with 1/2, RTs were faster with the SN fractions than with the SD, and LH faster than RH. Moreover, the target-standard absolute distance predicts RTs of fractions in both the LH and RH, while the target-standard componential distance predicts RTs of frac- tions when they were presented only in the RH. When the target was compared with 1, RTs with the SN fractions were the fastest. Only the target numerator-denominator distance predicts RTs of fractions presented in both hemispheres. Our results showed that during fraction processing the RH can use both a global and/or a componential approach, but the LH can use only a global approach. Task demands influ- enced the strategy used in our experiments.
