You might find interesting the correlation on gravity and mobile navigation. The thing is that some aspects of nature have to be taken in consideration when developing UI for mobile apps, and gravity is one of them. Well, not exactly gravity, but gravity's implications on how we hold our handhelds.
If you look closely on how you grab your mobile phone while using it with one hand only you will find out that there is a particular way to do it. Most of the pressure is at the center of your palm, with that one corner of the handheld sitting right on it, the other major pressure points are distributed across your middle and ring fingers, your index finger is commanding the tilt laying on the rear face of the phone and your pinky finger slides right below the thing keeping it locked within your hand. All of this to have the thumb free to cover the maximum radius possible across the screen.
This is why it is a best practice to keep everything at a thumbs reach when designing mobile interfaces.
Gravity is also the reason that on-screen keyboards in tablets provide a split layout, so that you can sit the tablet corners at the center of your palms, providing grip with the bends of your free commanding thumbs.
This actually goes back to the first mobile games such as the Nintendo portables in the 80’s (Yeah, those little ones before the NES) and even back with that little Mattel Electronics machine we used to play analog led football with (here’s a great website to go throwback on those handheldmuseum.com)
If we were to name the royalty of the one-hander devices, the iPod click-wheel would have a special place on the ranking for solving this problem beautifully before touchscreen devices made it's way to the masses. A bad example would be the tv remote, which is too long to handle with just one finger, but we cut it some slack just because it’s better than standing up and fixing the tube.
All the examples mentioned can illustrate that good handheld design has got to be based on ergonomics and user interaction, a concept that has ruled for very long in industrial design and architecture.
So, the consequences in software design are obvious if we extrapolate the rules from the hardware counterparts. If you want the users to have a comfortable experience, keep the controls at a thumbs swipe, put your call to action elements at the bottom of the screen where the interaction is likely to happen and avoid at all cost the need of a second hand to navigate through the app.
Also remember that when tapping on things, you don't want the users hand to cover something you are about to show (think of the floating action button menus), so this might give you a better idea of where to place a button that reveals further actionable items.
These are just a few basic rules of how to better design mobile and responsive applications, and a brief passage of how nature and ergonomics dictate the guidelines to create the tools we use to make our life easier.
Do you have other examples of ergonomics in software design? Let everybody know.
Thanks for reading through.