Doing as they are told and telling it like it is: self-reports in mental arithmetic.

Adults (n=64) solved single-digit multiplication problems under both speed and accuracy instructions. Half also provided self-reports of their solutions to the problems. The participants with relatively low levels of arithmetic fluency were most influenced by instructional requirements. They responded more slowly and accurately when asked to provide descriptions of their solution procedures, whereas the performance of the participants with high and average levels of arithmetic fluency did not change. Furthermore, the performance of the low-fluency participants was more affected by speed and accuracy demands than was that of the other individuals, but only when the low-fluency participants were also required to provide self-reports. Accordingly, models of mental arithmetic will need to include roles for individual differences and situational factors.