This past weekend, I attended the conference he was interviewed at for this article. During his talk, he mentioned he had them complete the VVIQ from University

This past weekend, I attended the conference he was interviewed at for this article. During his talk, he mentioned he had them complete the VVIQ from University of Exeter (which the other replies linked to), the Plymouth Sensory Imagery Questionnaire (https://www.plymouth.ac.uk/research/psychology/imagery https://www.plymouth.ac.uk/research/psychology/imagery), plus several more questions, maybe a dozen or so.