If you have any book titles in particular, I would be very interested. I've been meaning to head down to the library soon anyways.
I have read bits and pieces about the visible heat concept, but to my understanding they can still differentiate between light and visible heat to some small degree, and as far as photoperiods go, while they can "see" heat at night, it does not cause the same level of stress that a visible light would cause (for example, while they are definitely aware of a CHE at night, a CHE does not cause the same stress as a halogen bulb would). At least this is my understanding of it, please correct me if I'm wrong.