Emotional targets: evaluative categorization as a function of context and content.

Event-related potential (ERP) studies of early evaluative categorization have often used variants of an oddball paradigm to assess attention to target stimuli as a function of content (i.e., valence) and context (e.g., presentation among non-targets differing in valence). However, most previous studies have not fully crossed content and context, and have not examined the time-course of these effects. The purpose of the current study was to investigate these two issues in an effort to further clarify the nature of evaluative categorization as reflected in the late positive potential (LPP). Pleasant, neutral, and unpleasant images served as both targets and non-targets in an emotional oddball task. Results indicate additive effects of emotional content and target status on the early portion of the LPP; however, the LPP did not differ between pleasant and unpleasant stimuli. Only target status modulated the later portion of the LPP, suggesting different contributions of cognitive-affective processes over time during evaluative categorization.