How do incorrect results change the processing of arithmetic information? Evidence from a divided visual field experiment

Despite several recent important developments in understanding numerical processing of both isolated numbers and numbers in the context of arithmetic equations, the relative impact of congruency on high-level compared to low-level processing remains unclear. The current study investigated hemispheric differences in the processing of arithmetic material, as a function of semantic and perceptual congruency, using a delayed answer verification task and divided visual field paradigm. A total of 37 participants (22 females and 15 males, mean age 30.06, SD 9.78) were presented unilaterally or bilaterally with equation results that were either correct or incorrect and had a consistent or inconsistent numerical notation. Statistical analyses showed no visual field differences in a notation consistency task, whereas when judgements had to be made on mathematical accuracy there was a right visual field advantage for incorrect equations that were notation consistent. These results reveal a clear differential processing of arithmetic information by the two cerebral hemispheres with a special emphasis on erroneous calculations. Faced with incorrect results and with a consistent numerical notation, the left hemisphere outperforms its right counterpart in making mathematical accuracy decisions.