One plus one is less than two: Visual features elicit non-additive mismatch-related brain activity

► Different deviant visual features elicit different mismatch-related brain activities. ► Feature-related mismatch responses are non-additive. ► Activity to two deviant features is identical to the response elicited by single feature with more effective processing. ► Polarity of the mismatch response depends on the stimulated half field.