This was talked about in the 'PS1 strange resolutions' thread. Grab a copy of any game you like, halve the resolution of a copy in each direction and then rescale back to original. Half vertical res is definitely more noticeable, but it'll probably depend on the game. My guess is our environment tends to have thinner objects more horizontally aligned than vertically, such as thin window lintels versus thicker frames, or thin power/phone cables versus thicker posts supporting them, and our perspective to the ground makes many thin shapes out towards the horizon. But as it's so easy to test oneself, the only research needed is one's own.