Option + arrow left/right moves window rather than moving caret Normally, I would expect that when I hit option plus left arrow or right arrow the cursor (caret) would move back/forward one word. And if I hold shift I would expect to easily highlight the words as I move along. In fact there are questions that mention this behavior (How to use Ctrl+left/Ctrl+Right (instead of Alt+left/Alt+right) to move to the previous/next word)

The current behavior I have observed is that instead of moving the caret the width of the window is adjusted by maybe 50-100 pixels smaller or bigger by moving the right side of the window.

How can I get the functionality I expect?

Version:
OS X El Capitan
10.11.6

EDIT:
I've also noticed now that command + left/right seems to switch windows rather than going to the start/end of the line. I would like this to be changed back as well.
This can be caused by custom software. In my case the problem was that I was running the window management tool Slate which changes this with it's default configuration.