Affective Reactions to Aversive and Appetitive Cues: Evaluative Process and Emotional Arousal

The present thesis investigated the evaluative process and information provided by different stages of emotional processing in the evaluation of natural scenes. The competing hypotheses, that the evaluation is driven by the emotional significance (arousal) or by a specific valence category, were tested. Experiments 1 and 2 investigated the functional differences between the appetitive and defensive gradients described by the neural response (indexed by the Late Positive Potential and the Alpha-desynchronization), the autonomic changes (skin conductance), and the subjective evaluations of emotional pictures. The results showed that the motivational gradients defined by the physiological response do not differentiate appetitive and aversive stimuli, while the subjective evaluation suggests a steeper negative gradient. Experiments 3 and 4 investigated the differences in attentional engagement to highly arousing distractor pairs of the same (pleasant or unpleasant) or opposite valence (pleasant and unpleasant). The results suggested that all stimuli are evaluated in terms of significance when attentional capture is triggered, regardless of the distractors’ valence. Experiments 5 and 6 investigated the engagement and disengagement components of spatial attention in an instructed saccades dynamic-task. The results suggested that, in this specific task, only the disengagement component of spatial attention is affected by the stimulus significance. Altogether, the present results suggest that the evaluation of affective stimuli and the attentional engagement toward them, is closely related to the emotional significance. Because the ability to evaluate visual stimuli is essential for our survival and well-being, the evaluative system might have evolved to detect significant stimuli in the environment, regardless of their valence. Thus, only in later stages of emotional processing aversive stimuli are evaluated as increasingly more arousing than appetitive ones.