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Behavioural and neurophysiological studies of task‐switching have tended to employ ‘bivalent’ stimuli (which afford responses in two tasks). Using brain potential recordings, we investigated task‐switching with ‘univalent’ stimuli affording responses in only one of the tasks, and compared the outcomes to those recently obtained with bivalent stimuli (Lavric et al. [2008]: Eur J Neurosci 1‐14), in order to examine two phenomena. First, when only univalent stimuli are presented, the processing of task cues becomes optional. Our results showed that in these circumstances linguistic (but not pictorial) cues were still effective in eliciting at least some degree of preparation for a task‐switch, as evidenced by the reduction in the error cost of switching at the longer preparation interval and by a posterior switch‐induced ERP positivity at about 450–800 ms in the cue‐stimulus interval. Second, single affordance stimuli not only …