P300 differences for target (.10), nontarget (.10), and standard tones
(.80) were assessed using a three-stimulus oddball paradigm in which
participants responded only to the target (n = 12). Target/standard (e
asy or difficult) and nontarget/standard (large or small) pitch differ
ences were manipulated orthogonally. In all conditions, target tones e
licited a parietal P300, which was affected only by the target/standar
d discrimination ease. Nontarget in the easy/large and difficult/small
conditions elicited a parietal but smaller P300 than the target but i
n the easy/small condition elicited similar ERPs to the standard. Howe
ver, nontarget stimuli in the difficult/large condition elicited an an
terior maximum and earlier P300 (P3a) component. The findings suggest
that target P300s are not influenced by the nontarget stimulus configu
ration, whereas the nontarget P300 outcomes are determined directly by
the stimulus context. The theoretical implications are discussed.