Rule of thumb
I concur with Lobbygow:
The adoption rate of any new tehnological (sic) gadget, gewgaw or gizmo will be directly proportional to the extent to which it engages the thumb in an intuitive and enjoyable manner. When it comes to navigating content, this effect is even more pronounced.
January 17th, 2005 at 3:19 pm
No, no, Scott Adams nailed this one first. All inventions in history cater to one of three major motivations: greed, laziness and lust. The more a gadget caters to one or more of these motivations, the faster it will be adopted.
The reason you see a thumb correlation is that something you control with your thumb only requires one hand to control, thus greatly expanding its “lust” capacity.