Effects of colour and lexical relevance on irrelevant stimuli: event-related potential results

Event-related potentials (ERPs) were recorded in a warning stimulus-imperative stimulus (S1-S2) situation where S1 was either a coloured bar followed by a letter string (S2), or vice versa. When S1 was a coloured bar, reaction time (RT) response was required only to words which were preceded by a bar of a particular colour. When S1 was a letter string, response was required only to bars in a particular colour which were preceded by a word. Contingent negative variation (CNV) appeared only after those S1s which could be followed by a target stimulus. However, bars in the colour of the target elicited attention-related ERP components even if these stimuli were preceded by non-words, i.e. when the subjects could be certain in advance of the appearance of a non-target stimulus.