When we interact with a touch screen, we expect a certain “directness”; that is, if I grab something and push up, I expect that thing to move up. Like dragging a web page up or down. However, did you ever notice that on a track pad (like on a laptop), the direction is reversed?
- Trackpad: fingers move DOWN, position indicator goes DOWN, web page goes UP
- Touchscreen: fingers move DOWN on surface, position indicator (on far right) goes UP, web page goes DOWN
It’s so subtle, perhaps you’ve never noticed it so I made a video:
I sometimes use this inconsistency (position indicator goes down, fingers go down, but screen moves up) in my class as an example of a violation of an old display design guideline called the principle of the moving part. It suggests that when you have an indicator on a display, it should move in the same direction as the thing it’s indicating. The touchscreen/trackpad issue is more complicated because you also have an input incompatibility (fingers and display moving in opposition).
The difference between the touchscreen and trackpad is in what the fingers are “controlling”: the screen or the position indicator?
Am I obsessing over a trivial issue? Probably; this is something that you just get used to. But I seem to not be alone in noticing this issue. Apple, in their next version of their operating system, will make trackpad navigation consistent with touchscreen navigation (fingers move DOWN on surface, position indicator (on far right) goes UP, web page goes DOWN). Fortunately for some users, it is a user-selectable feature: