Abstract: Mental arithmetic, an important thinking activity, is one of the subjects incognitive psychology. There is an obvious problem--size effect in mental arithmeticwhich has close relation with working memory and long--term memory, and researchon mental arithmetic from interdiscipline (e.g., coghitive psychology, neuroscience) isa main direction in the future.

Key words: mental arithmetic, Problem-size effect, working memory, long-termmemory