Up until Mountain Lion, in OS X there was always an option to switch smooth scrolling on and off. I think it was a checkbox called ‘Use Smooth Scrolling’ in the Appearance section of System Preferences. An example of smooth scrolling is in Safari, where if you are viewing a web page and hit space then without it the page just immediately jumps to the next section, whereas if you have it on you see it very quickly scroll down to the next section. However, in Mountain Lion this option no longer exist and smooth scrolling seems stuck on.
If this annoys you then you can still turn if off by opening Terminal.app and entering:
defaults write -g NSScrollAnimationEnabled -bool NO