After installing Ubuntu 12.10, the first thing I wanted to do, was to disable reverse scrolling – you scroll down and it scrolls up! This is also called natural scrolling by Apple. Don’t know what is natural about it but may be natural for Apple users.
Open the terminal and edit this file using any editor and edit the .Xmodmap in your home directory for example:
Here you would seet his:
pointer = 1 2 3 5 4 6 7 8 9 10 11 12
You would note that in the sequence of numbers 5 and 4 are interchanged. Change it back to the sequence..
pointer = 1 2 3 4 5 6 7 8 9 10 11 12
Now you are done, logging out and in should do the job.
If you have Ubuntu Tweak installed. Just go to Tweaks-Miscellaneous and you would see an option to toggle Natural Scrolling on/off.