The research work reported in this paper addresses the question whether retest practice changes the speed-ability relationship. In three successive test sessions several cognitive tests of attention, memory and working memory were administered: Attention Switching Task, Continuous Attention Task, Memory Scanning Task, Letter Comparison Task, and Maintenance Summation Task. Retest practice led to substantial decreases of mean reaction time in the memory and working memory tasks while in attention tasks the effect was small or even insignificant. Intercepts, slopes and components representing sources with a constant, increasing and decreasing influence on responding were computed and correlated with ability. The results revealed that the correlation of the Letter Comparison task was large independently of retest practice. In contrast, for the Maintenance Summation Task the highest correlation was observed for the component representing the source with an increasing influence. Some retest practice seems to be necessary in order to establish the relationship of working memory and ability.