Reflexive eyeblinks to a startle probe vary with the pleasantness of a
ffective pictures, whereas the corresponding P300 varies with emotiona
l arousal. The impact of attention to the probe on these effects was e
xamined by varying task and probe type. Probes were either nonstartlin
g tones or startling noises presented during affective picture viewing
. Half the participants performed a task requiring attention to the pr
obes; the other participants were told to ignore the probes. Blinks to
the startle probe varied with picture pleasantness for both task and
nontask conditions. In contrast, P300 magnitudes for both startle and
tone probes were reduced during emotionally arousing pictures, irrespe
ctive of pleasantness, in task and nontask conditions. Further attendi
ng to the startle probe prompted an augmentation of N100 during unplea
sant pictures. The data suggest that affective modulation of probe res
ponses reflects obligatory processes in picture perception.