Way back in June when I started working for the startup I’m working for now, I made an observation about how people will use their smart phones–a fact which was ignored, and which I believe is hurting our app now. And it reflects how we use different computing form-factors in general.

A desktop is not a laptop is not a pocket computer.

A desktop is an immersive environment. Consisting of a very large display screen and keyboard, a desktop computer is something that generally has a fixed location, but can have a lot of attached or non-portable devices that allow you a great deal of power. Desktop computers are perfect for the daily grind of working at a fixed location.

Laptop and portable computers are less immersive simply because they are smaller. In general, you use a laptop computer by sitting down at a given fixed location, setting up your environment (pull out laptop, open it up, turn it on, find a wireless connection, plug it in), and working. Battery life for a laptop is not all that important unless you set up in an area without an outlet–at which point battery life is invaluable. Battery life is also invaluable if you use a laptop to go from meeting to meeting, where setup time needs to be as short as “take out, flip open.”

Phone computers are the least immersive device, and the one that interests me the most because it is the one that is the least understood. The few people I’ve talked to about phone computers have talked about creating compelling immersive environments for the phone–and tackling the problem of figuring out how to create an immersive environment on a tiny form factor. But phone computers are not immersive.

Certainly there are “immersive” games being designed for the iPhone computer. But there are also a lot of people who seem surprised that some of the most successful applications for the iPhone are things like fart jokes. The reality is that these successful tiny applications are not simply successful because the App Store is improperly structured–though this contributes. No, they are successful because people use the iPhone differently than they use laptop computers.

You see, most people use the phone in the following way:

(1) They pull it out of the pocket and press the “unlock” key.
(2) They tap a few keys. Perhaps they’re getting someone’s phone number, or placing a call, or pulling the finger.
(3) They then put it back into their pockets.

In other words, the tiny, non-immersive form factor combined with a non-existent setup time (as compared to laptops or desktops) means that most interaction with the phone is going to be a very quick cycle of “pull it out, ask a question, get an answer, put it back.”

Now there are times when people are using their phones for an extended period of time. But that extended period of time will stem from two sources. First, a user may be stuck on a subway or in an airport and have nothing to do–at which point they’ll use the phone as a source of entertainment. They’ll pull it out and watch a movie or TV show, or browse the web, or play a game. Because they’re in a circumstance where they’re killing time, however, the game or program should be able to save state quickly, and be entertaining immediately. A first person shooter that has no objective but quickly blowing people away makes more sense than a ‘capture the flag’ game or a game which takes some extended period of time to complete the level: you don’t know when the user will be back on the subway or stuck in an airport. And he may only be killing five minutes.

The second reason why a user will continue using an application (IMHO) is when he pulls it out, asks a question–then doesn’t get the answer he’s looking for, so re-asks the question in a different way. But this is not a good model of user interaction: the user is not interacting with your application because they’ve suddenly gone into an immersive interaction. They’re frustrated! because they’re not getting the answer they want.

Because of this, information-providing applications should provide information quickly. All the usual rules of computer-human interaction apply: 1/4th of a second is the longest delay between touching something and having it react. Two to four seconds is the longest delay for doing some computation–and during this time a spinning animation should be shown. If there is something that requires more time (such as getting the GPS location or hitting a server), a status display should be put up if this takes more than 5 seconds, letting the user know exactly what the software is doing. And if the entire interaction takes longer than perhaps 15 seconds, you better have a very good reason why–because chances are the user is going to flip the application off and put it away, unless he really needs the information.

But the bottom line is this: if your application provides information, it needs to work in a very quick cycle of “pull the phone out, ask a question, get an answer, put the phone away.” If you are designing your application to be an immersive environment or to function in any way other than in a “pull it out, ask a question, get an answer, put it away” loop, you’re designing your application for failure.