# squinting and brightness **URL:** \ **Category:** Factual Questions\ **Created:** [January 13, 2003, 10:15pm UTC](https://boards.straightdope.com/t/squinting-and-brightness/148388 "2003-01-13T22:15:13Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![jb\_farley](https://avatars.discourse-cdn.com/v4/letter/j/9d8465/32.png) [@jb\_farley](https://boards.straightdope.com/u/jb_farley)\ **Post date:** [January 13, 2003, 10:15pm UTC](https://boards.straightdope.com/t/squinting-and-brightness/148388/1 "2003-01-13T22:15:13Z")
hello everybody, how come when it’s bright out, and both my eyes are open, i squint a lot, but when i close one eye, the open eye doesn’t have to squint as much? like, there’s an actual threshold of pain, and if i try and have both eyes open wide- it hurts like hell! but when i close one eye, the non-closed one can open much more. it’s weird, yo. jb ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 13, 2003, 10:53pm UTC](https://boards.straightdope.com/t/squinting-and-brightness/148388/2 "2003-01-13T22:53:45Z")
I’ve noticed this before (I think I might have even started a GQ thread on it too) - I would venture to suggest that it is because vision, or rather perception, takes place in the brain - your eyes don’t hurt because the light is too bright, but rather because your _brain has decided_ that the light is too bright; why this decision is apparently based on the sum of the input from both eyes is a very interesting question. I wonder if people (who for their entire lives have been) blind in one eye are able to tolerate less brightness than a person with one eye closed. ---
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [January 13, 2003, 11:00pm UTC](https://boards.straightdope.com/t/squinting-and-brightness/148388/3 "2003-01-13T23:00:59Z")
Perhaps when you close one eye, the other one closes a little, too.