A spectralanalytic approach to emotional responses evoked through picture presentation.

Frontal EEG asymmetry has been linked to emotional and motivational reactivity. A frequently applied method to provoke specific asymmetry profiles is the presentation of affective film clips. Although these films might elicit strong emotional reactions, the exact time course and peak of an affective response remains unclear. In an alternative attempt, stimuli from the International Affective Picture System (IAPS), known to reliably alter emotional states, are utilized. These stimuli are less likely to cause excessive variations in affective responding. However, relevant studies have most often been unable to find the predicted effects. One reason for such failures might be the inadequate knowledge about the minimum number of stimuli needed for psychometrically stable results. In the present study, an adequate split-half reliability for the experimental procedure was assured and substantial effects of affective picture category were found. This pattern of results was robust for both Cz and linked ears as reference. Thus, presenting pictures with an adequate recording length might be a reliable alternative for inducing affective reactions in alpha asymmetry research.