Effects of Predictive Information on Pupil Dilation during the Evaluation of Food Images

It has been well established in previous research that predictive information has a large impact on decision-making in a variety of cognitive paradigms. Less is known about how predictive cues influence the sensory, perceptual and affective processes toward a subjective choice. Here, we designed an evaluative decision-making paradigm, with naturalistic food images as stimuli, using predictive cues to measure pupil dilation during information processing toward a subjective rating. In each trial, we used a predictive cue to generate an expectation about the upcoming target image. The color of the cue indicated the predictive validity (either 100% or 50% reliability); the shape of the cue indicated the predicted valence of the target image (either appetitive or aversive). We also varied the length of the delay between the predictive cue and the target image (either 1s or 9s). The participants were asked to rate the target food images on a continuous scale from -10 to 10 using a joystick. The results showed a difference in pupil dilation in response to the predictive cue as a function of the predicted valence, with more constriction following negative cues. The dilation was unaffected by color. There was also a notable difference in pupil dilation during the target image viewing as a function of the actual valence, with more constriction for appetitive images. The apparent contradiction in dilation as a function of item category may be due to the level of arousal, with complementary or opposing functions for valence during expectation versus actual sensory and perceptual processing. Future research is required to establish the exact relationship with arousal in order to uncover the underlying mechanisms of this novel finding.