R Shift key now triggers exposé. Need help!

Whenever I press the R shift key, regardless of the application, exposé is always triggered. Specifically, it activates exposé for the current application in use. I did not modify any of the keyboard or exposé settings in system preferences. I created a new account to see if it was preference related, and the keyboard functioned normally in the test account. The problem is that I have no idea how or what preference was changed. I thought about trying to restore a preference folder with time machine, but I have no idea which file or folder contains the relevant preferences. I have scoured the internet for answers and have so far come up empty. Any help would be much appreciated.