A new study reveals the relationship between attentional state and emotions from pupillary reactions. Visual perception elicits emotions in all attentional states, while auditory perception elicits emotions only when attention is paid to sounds. Source: PlosOne
Emotions such as heightened arousal can make pupils dilate. Belladonna (or deadly nightshade) was once used by women to dilate their pupils, thus making them seemingly more attractive. Source: Wade, N. J. & Swanston, M. T. (2013), Visual Perception. An Introduction. 3rd edition, London, Taylor and Francis Group.