Why do some people have much more difficulty than others in learning a computer-based skill? To answer this question, we observed first-time users of computers as they learned to use a computer text editor. In two experiments, older people had more trouble than younger people and those who scored low on a standard test of spatial memory had greater difficulty than high scorers. These correlations were stable over several hours of practice and did not vary as a function of the type of terminal used or specific editing problems attempted. Correlations involving age and spatial memory could not be explained by other characteristics such as amount of education, reasoning ability, or associative memory ability. Results like these that relate learning difficulty to specific characteristics of people ultimately may suggest ways to change computer interface design or training to accommodate a wider range of users.