Imagery modulates the pupillary response, but this does not reliably index differences in imagery vividness

Most people report that they can imagine seeing things in their mind's eye. But there are large individual differences. A small proportion of people report that they can never visualise (aphantasics), and a similarly small proportion of people report that their imagined experiences are as realistic as seeing (hyperphantasics). The majority of people describe their visualisations as being moderately vivid. The ratings that inform imagery vividness analyses are subjective self-reports, but it has been suggested that imagery modulations of the pupillary response could be used as a physiological index of individual differences in imagery vividness. When we assessed this inter-relationship, we found that imagery can indeed modulate the pupillary response, with pupils becoming relatively more dilated if people imagine seeing dark, as opposed to bright scenes. However, imagery modulation of the pupillary response was not associated with individual differences in imagery vividness ratings. Overall, our data suggest that while imagery can modulate the pupillary response, this effect does not provide a reliable index of individual differences in imagery vividness ratings.