The default gestures for navigating in OS X
In OS X, you can activate Launchpad, Exposé and slide between full-screen apps using either three or four fingers to swipe across the trackpad. The default is four, but we prefer to use three. To change it, click on the More Gestures tab in the Trackpad pane, make sure the relevant items are checked. Choose ‘Three fingers’ from the dropdown menus. If you set swiping between fullscreen apps to use three fingers, make sure you also set the ‘Swipe between pages’ option to two fingers to avoid confusion.