Is there an objective test for aphantasia?

I read some time ago, possibly on this site, that one possibility is to measure someone's brain waves and ask them whether the green of trees is darker or lighter than the green of trees. Someone who can form images in their mind will apparently form an image of grass next to trees and compare them that way.Being color blind, that's a tough question for me. When I read that, I said to myself that obviously it was the green of the grass that was brighter, but then I realized that I was thinking about the bark of trees which I already know is often pretty dark (with some exceptions).

Great question Stephen. According to leading scientsts studying aphantasia we have some objective measures to measure it now, though the science is still evolving. One such measure is through Binocular Rivalry Experiments (BR). We wrote an article about BR here. Findings from a new study annouced late 2019 revealed that pupil contraction may also be another objective measure. We are still waiting to get our hands on a copy of this research paper once published. We post any new scientific discoveries we stumble on in our evolving database The Aphantasia Index. fMRI studies are also another objective measure, though particpation in such studies is very costly and not widely availabe to the public. As we build the network, we hope to make some major contributions to advance the science on more objective testing.