Pupil dilation response to nicotine-related visual stimuli in smokers and non-smokers.

Visual-spatial attention is the process through which we direct our attention to a certain object or scene. We can process visual information more quickly and recall the specifics of what we are seeing when we pay close attention. Biases in attention appear to be a critical part of addiction with an impact on craving levels because drug-dependent people are more prone to have their attention grabbed by drug-related environmental stimuli. Making use of the previously established connection between eye movements and spatial attention, we used eye-tracking techniques to research the indicators of attentional priority in smokers. We found in cross-validated logistic regression, that the pattern of pupil dilatation and constriction in response to visual stimuli related to nicotine could successfully predict the smoking status of both women and men. In contrast, standard proxy metrics based on reaction times or eye location were less accurate. Lower nicotine dependence levels resulted in more pronounced pupil constriction, corroborating earlier assertions that the incentive value of conditioned stimuli gradually declines and makes room for a more automated, habit-driven processing mode. Additionally, pupil size became more sensitive with longer periods of abstinence, indicating that it might reflect the intensity of cravings. We conclude that pupillometry can serve as a reliable marker for the computation of attentional priorities and offer helpful cues about motivational conditions and individual attitudes toward conditioned stimuli.