Abstract: A study on menta arithmetic with increasing of age and its mechanism wasaccomplished in 172 normal subjects of from 20 to 79 yeare of age. Five mentalarithmetic tasks, "1000- 1", "1000-3", "1000-7", "1000- 13" , "1000- 17", weredesigned with a serial calculation in which the subjects sequentially subtracted thesame prime number (1, 3, 7, 13, 17) from another number 1000. The results indicatedthat: (1) There was an obvious interaction between age and mental arithmetic, andmental arithmtic efficiency (the ratio of accuracy to RT) decreased in power funtionwith the advancing of age; (2) There were two mediators (latent variables) which wererelative to speed component and non-speed component respectively in the aging processof menta arithmetic, and speed component had significant effect on non-speedcomponent.

Key words: mental arithmetic, age, Structural Equation Modelling (SEM)