Psychophysiological studies of emotional perception often use stimulus sets containing a greater proportion of emotionally arousing, relative to non-arousing stimuli. However, there is evidence suggesting that participants may learn to anticipate more common stimuli, and this differential expectation may bias reactivity at presentation. Here we manipulated emotional and neutral stimulus set proportions across two studies to investigate the potential role of emotional stimulus probability on central and peripheral indices of emotional scene perception. In study 1, (n=72) viewed a series of 168 scenes containing an equal number of emotional and neutral stimuli, while study 2 (n=72) included twice as many emotional as neutral stimuli. This manipulation did not yield a significant interaction across the 2 studies. This result suggests that commonly used stimulus proportions over-representing emotional stimuli do not result in expectation biases. Future work may investigate more extreme stimulus proportions to identify the threshold at which expectations influence reactivity.