The second paragraph of this Guardian article mentions, and links to, but doesn't expound on the biophysical pupillary response to mental visual imagery.
If someone with normal mental visualization ability pictures a "bright" scene, the pupils contract just as they would in response to a bright visual stimulation. Aphants' pupils show no physical response to this test.
https://www.vice.com/en/article/qjbq8w/how-pupil-size-can-re...
If someone with normal mental visualization ability pictures a "bright" scene, the pupils contract just as they would in response to a bright visual stimulation. Aphants' pupils show no physical response to this test.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9018072/