Ubuntu 11.10 is shiped with a default System Setting control panel in which you can not tweak advance settings. In order to get it done you have to install the Gnome Tweak Tool. Use the following command to install Gnome Tweak Toolin your Ubuntu 11.10 Oneiric Ocelot.
sudo apt-get install gnome-tweak-tool
Click on he Advanced Settings icon.
Here you go with your changes…
Have a great day with Ubuntu 11.10 Oneiric Ocelot