It might be interesting if the three eyes could work independently. If binocular vision was not currently needed, the two outer eyes could diverge and widen the field of view. The middle one filling in the gap.
Evolution might have set such a thing up. Also allowing for quick shift of the middle eye to add depth if something drew attention in the wider field of view on one side. Evolution might also have added compensation features to the middle eye. If one outer eye had a defect or was lost, the middle would take over a more completely standard binocular duty or would adjust focus intermittently to adjust to a poor other eye problem.
A third central eye would likely evolve some useful difference. The two outer ones being the same as our present ones. But the central one evolving a useful extra. Infrared would be interesting. Night hunting or survival. The cat eye system for better night vision in general. Evolution could then maybe justify the cost benefit analysis.
I have often wondered what an animal such as a Chameleon sees. It can rotate it’s eyes to wide degrees, where there would be no common visual overlap of the two eyes. Do folks with very divergent wandering eyes have a dark area?
According to the third blurb in this fairly classic-looking website about falling into a black hole, trinocular vision would help with seeing clearly in highly distorted spacetime, in what short moments may remain of your life under those conditions.
Paging Nick Danger…
…also nuns, I’ve been given to understand.
And Miss Michaud, my all-seeing 5th grade teacher. Curses, foiled again.
I think a third eye would make us less intelligent. As the third eye would use up resources in the brain.
The same way having four arms would.
Also Superman, in one Red Kryptonite story (scroll about halfway down)
in “The Menace of Red-Green Kryptonite!” (Action Comics #275, April 1961), Brainiac hits Superman with a combination of Red and Green Kryptonite, which gives Superman a third eye in the back of his head.