I am wondering if there has been any studies on the usability of trackpads in laptop computers because they have always seem rather awkward to use yet have become standard with laptops. It doesn't mimic the mechanics of using a mouse because the physical placement of the hand is different when using the trackpad. Why has it been designed this way and is there any ergonomic assessment to suggest it has actually been designed for ease-of-use?
A touchpad is indeed more awkward to use than a mouse:
MacKenzie IS, Kauppinen T, & Silferberg M, 2001. Accuracy measures for evaluating computer pointing devices. Proceedings of CHI, 3(1), 9-16.
…and MacKenzie et al. used a large-sized touchpad. The dinky ones on most (non-Apple) laptops are even worse. I know it pains me to watch a user shift between the back button and the scrollbar in a browser, a common move that takes multiple swipes at the touchpad each time. Personally, I use a small wireless mouse whenever I can.
So why have touchpads on laptops? Because sometimes you can't use a mouse. When literally on top of your lap, you can’t rely on there being a flat surface for a mouse. If no mouse, what else is there? A track ball is no better than a touchpad. A joystick is worse (ibid), and so is the trackpoint “eraser head” semi-isometric joystick seen on some older IBMs.
Sutter C, & Ziefle M, 2006. Psychomotor performance of input device users and optimized cursor control. Proceedings of the HFES 50th Annual Meeting, 742-746.
I suspect it was studies like Sutter & Ziefle that led to the extinction of the trackpoint, which was about the only serious competitor to the touchpad.
Touchscreen is certainly an alternative to a touchpad, as its performance rivals the mouse:
Forlines C, Wigdor D, Shen C, & Blakrishnan, R, 2007. Direct-touch vs. mouse input for tabletop displays. Proceedings of CHI, Mobile Interaction Techniques I, 647-656.
...but only for UI elements sized to deal with a fat finger, not necessarily for “classic” GUIs with small elements intended for mouse use. So, it’s probably good to have the touchpad as a backup to the touchscreen, although this burdens the user on deciding when to use one versus the other, and make the switch between them.
One advantage of the touchpad (and touchscreen) over the mouse is the support of gestures. There’s pinching, of course; how about a circular motion for scrolling? It may be better than the right margin swipe on some laptops:
Arthur K, Matic N, & Ausbeck P, 2008. Evaluating touch gestures for scrolling on notebook computers. Proceedings of CHI.
However, a mouse can make up for gestures by having auxiliary controls (e.g., the scroll wheel).
I don't know what you can do to make touchpads more usable. A larger pad helps, I suppose, maybe making them large enough to be like using an invisible mouse. However, there seems to be something about the tactile feedback of pushing a physical object like a mouse. With a large touchpad, maybe you could electromagnetically vary the surface of the pad to represent the windows and controls on screen, so users can literally feel window edges and buttons. That might make up for its deficits to the mouse (although you could do the same with a mouse by putting small height-varying "feet" on its bottom).
As an alternative to the touchpad, maybe we should be thinking about how to make a mouse work with a laptop on top of the lap. Maybe you can make a laptop with a slide-out mouse pad that's rigid enough for practical use. Might be worth it at least for the larger laptops.
Providing tactile feedback might help with tapping the touchpad to select:
MacKenzie IS, & Oniszczak A, 1998. A comparison of three selection techniques for touchpads. Proceedings of CHI, 336-343.