Google’s head of Android user experience, Matias Duarte is engaging Google+ users with some in-depth answers to pressing questions about the Nexus and Android experience. As of this writing, he’s still taking questions and there’s no shortage of discussion on the answers he’s already provided. So far, we’re taking a look at why there are no SD cards in Nexus devices and why on-screen buttons are consistent in Jelly Bean?

We’ll continue updating the post as more answers arrive.

Google+ Matias Duarte

Why did you make the system buttons and status bar consistent across all devices in Jelly Bean?

Consistency and usability are really important to us, and that’s something we strive to improve in every new version of Android. With Honeycomb we first introduced the idea of a completely onscreen navigation UI which gave us unprecedented flexibility in how that UI adapts and transforms – both when you turn the device in your hands and when the software changes and has different control needs. Now in Jelly Bean we’ve made the universal software navigation buttons and system bar consistent across all screen sizes.

This new configuration is based on usability research we did on all of the different form factors and screen sizes that Android runs on. What mattered most of all was muscle memory – keeping the buttons where you expect them, no matter how you hold the device.

Phones are almost always used in portrait mode, flip sideways occasionally, and never go upside down. As screen sizes get larger though, any which way goes. Imagine the frustration you’d feel if every time you picked up a tablet off the table ‘the wrong way up’ you found yourself reaching for a home button that wasn’t where you expect it to be? That irritation adds up and over time like a tiny grain of sand in your shoe and undermines the rest of your experience.

The Jelly Bean system bar always keeps the same 3 buttons where you expect them. This happens dynamically for every screen size, up until you get to small handheld screens where stacking the bars in landscape mode would leave too little vertical space.

The second thing we discovered was that there are almost as many different ways of holding our devices as there are people. In fact people love to use their Nexus so much that they use them for such long periods of time that having a single ‘correct grip’ is actually counter productive and increases hand strain. The Jelly Bean navigation buttons work equally well for left handers and right handers, one handed use, or two handed use, and for devices you’re carrying, resting on your knee, or putting on the table.

Last but not least, by unifying the design we are now able to put Notifications and Quick Settings right where you’d expect them, and only one swipe away.

Why don’t Nexus devices have SD cards?

Everybody likes the idea of having an SD card, but in reality it’s just confusing for users.

If you’re saving photos, videos or music, where does it go? Is it on your phone? Or on your card? Should there be a setting? Prompt everytime? What happens to the experience when you swap out the card? It’s just too complicated.

We take a different approach. Your Nexus has a fixed amount of space and your apps just seamlessly use it for you without you ever having to worry about files or volumes or any of that techy nonsense left over from the paleolithic era of computing.

With a Nexus you know exactly how much storage you get upfront and you can decide what’s the right size for you. That’s simple and good for users.