Emotional arousal has been linked to the motivation to socially share information with others and can reliably be detected in the voice. This is highly relevant for applied consumer research, especially given the recent availability of automatic arousal detection software. In an experiment, we studied how emotional arousal varies with intrinsic involvement, operationalized by participants’ preferential choice of upcoming movie trailers. In addition, were explored the effect of extrinsic rewards, operationalized by monetary incentives. Emotional arousal is inferred from the participants’ spoken reviews of their selected trailers, both automatically by a validated classifier and by an independent group of human judges. Positive intrinsic involvement – that is, reviewing one’s preferred trailer – and extrinsic rewards induce higher vocal arousal as perceived by listeners, which is associated with more subsequent social sharing of trailers and higher persuasiveness ratings of the reviews. In comparison, arousal inferred by the automatic classifier shows smaller differences between experimental manipulations. Overall, results support the notion that arousal plays a causal role for the decision to socially share an experience – an effect that should be of high interest for marketeers.