Abstract Two purposes motivated this study: (a) to quantify the difficulty in learning various symbols of the alphabet used to enter data into a personal digital assistant (PDA), and (b) to investigate the interaction of item difficulty with practice conditions that promote varying levels of cognitive effort. Levels of compatibility between members of the PDA alphabet and English were quantified through introspective ratings in Experiment 1 and objective performance measures in Experiment 2. Three levels of item compatibility were learned under conditions of proactive or retroactive augmented information in Experiment 3. Contrary to expectations, the item similarity effect did not interact with practice schedules—a retroactive augmented information condition resulted in degraded levels of acquisition performance, but superior retention levels, compared to the proactive condition. These findings are discussed in terms of the relative merits of cognitive effort in skill acquisition.