Are you unable to visualize images in your mind, with what is sometimes called the mind's eye (https://en.wikipedia.org/wiki/Mind%27s_eye)?
Use only two types of answers ("Yes" or "No") for the phenotype.
Read more about aphantasia:
http://www.bbc.com/news/health-34039054
http://www.nytimes.com/2015/06/23/science/aphantasia-minds-eye-blind.html
https://www.facebook.com/notes/blake-ross/aphantasia-how-it-feels-to-be-blind-in-your-mind/10156834777480504