Lucidi, A. & Barrouillet, P.
Department of Psychology, University of Geneva, Geneva, Switzerland
The aim of the present study was to identify the factors underlying individual differences in working memory (WM) capacity. According to the Time-Based Resource-Sharing (TBRS) model, there are at least two factors that should play a crucial role: processing efficiency and the efficiency of the refreshing mechanisms. This hypothesis was tested in three experiments. In Experiment 1, a computer-paced complex span task was used in which low-span and high-span individuals had to maintain series of letters while adding 2 to series of digits. Large individual differences were observed between the two groups. In Experiment 2, processing times were equated between groups by asking low-span individuals to add 1 instead of 2 to each digit. Individual differences were reduced but still significant. In Experiment 3, processing times were again equated and the time available to refresh memory traces was tailored to the processing speed of each group. This last manipulation resulted in a further reduction of individual differences, with no differences between low-span and high-span individuals in some conditions. This strongly suggests that both processing efficiency and the efficiency of the refreshing mechanisms are main factors underlying individual differences in WM capacity.