The Programme for International Student Assessment (PISA) index of interest in computers was derived from the students’ responses to the following statements: it is very important to me to work with a computer; to play or work with a computer is really fun; I use a computer because I am very interested in this; and, I forget the time, when I am working with the computer. A two-point scale with the response categories ‘yes’ and ‘no’ was used. The indices were derived using the WARM estimator. For information on the conceptual underpinning of the index see Eignor et al. (1998).