Kahneman and Treisman (1984, p.55) have succinctly described the main disagreement between early selection and late selection theories of attention: 'The classic question of attention theory has always been whether attention controls the build-up of perceptual information, or merely selects among the responses associated with currently active percepts.' Early selection theories hold that attention serves to select which one of a number of stimuli will be further semantically processed and stored in long term memory. On the other hand, more recent late selection theories maintain that selective attention operates after all stimuli are