[lupire]

Feynman's examples is of people being more critical about certain issues. A better example is the case of "radiation" that could only be seen in a dark room in the corner of your eye, which turned out to be a human visual artifact and wishful thinking.

[perl4ever]

I assume you're thinking of N-Rays and Blondlot, but there is another phenomenon that more or less fits your description.

https://en.wikipedia.org/wiki/Cosmic_ray_visual_phenomena

It's interesting that according to the Wikipedia article it's not entirely certain whether the radiation is producing actual light or just the sensation of light.