An example of stimulus sequence is shown for runs in which subjects attended to the left side. Two visual letter-streams were presented randomly to the left and right visual fields, including two task-relevant letters (‘A’,’X’, each 30% of the total events). The task of the subject was to fixate on the central white cross and to detect ‘A’ versus ‘X’ in a 2-AFC on the designated (i.e. attended) side only. Two-thirds of the lateral visual letters (both attended and unattended) were accompanied by simultaneous, centrally presented, spoken letter sound, 50% of which were incongruent with the visual letter and 50% congruent. Subjects were instructed to ignore the central spoken letters.