From the book...

Suspicions about what the aliens really look like have haunted UFO researchers for years. Some think that the human-looking entities, such as the blond "Nordics," might actually be screen memories imposed by the aliens. Behind the mentally imposed human mask lies the actual alien face, they say, though what the real underlying face looks like might be difficult to uncover. In one case, a witness told California psychologist Richard Boylan that she had encountered a "spaceman." When he invited her to look closely at the face of the "human" spaceman, she replied, "Oh my! It's not human after all, it's one of those Grays." But when he then suggested that she look closely at the face of the Gray, she realized that the Gray was actually a reptoid.

The real nature of these aliens is obviously quite elusive. One case in particular drives the point home. It took place on the night of May 30, 1974, in South Africa. When asked by the hypnotist what the aliens looked like, the witness replied, "They looked how I wanted them to look..."