Is one hand better than two?

For years, smart-phone designers have built products around the premise that people should only have to use one hand to look up a contact, scroll through e-mail, or answer a call. Think of a business traveler rushing through an airport, trying to check voice mail while searching for the gate and recaffeinating.

But Apple, as it is wont to do, headed in the other direction with the iPhone. If you've got long, flexible fingers you can use the iPhone with one hand, but most of us have to use two to do just about anything on the iPhone's touch-screen interface, as shown in the demonstration videos produced by Apple.

The smart-phone industry is still very young, relatively speaking, so it's not like these design goals have been set in stone. But the iPhone is forcing the industry to rethink the one-handed method, if only because sacrificing that piece of design dogma has allowed Apple to make a breakthrough with the user interface on the iPhone, according to several consumer electronics design experts interviewed for this article.

"Right now, we are going through this phase where it's really open-ended," said Mark Rolston, senior vice president of creative for Frog Design. "Nobody's talking in the traditional vocabulary, they are all thinking about what we are trying to accomplish in terms of usage."

The smart phones that most people are familiar with--the Nokias, BlackBerrys and Treos--only require one hand for basic operation. Obviously, typing on the QWERTY keyboards used by most of those devices is a two-handed operation, but navigating through the menu, looking up a contact, and using countless other functions only requires a single hand.

"Everyone is still trying to make a one-handed product," Rolston said. "It's the easiest way to distinguish a truly portable device from a workstation. Handhelds are about doing something else (while using the handheld), they fit within the context of people's active lives."

To achieve those goals, one-handed phones have to have real buttons--famously dismissed by Apple CEO Steve Jobs--that give people the ability to feel their way around a keypad, said Gadi Amit, founder and principal designer of New Deal Design. "People are getting so visceral with their phones; they can pick up the phone in the middle of the night and know what button to hit."

Try doing that with the iPhone. The lack of tactile buttons--except for the home button--has forced Apple into a two-handed mode of operation because users need to have the phone directly in front of them, with their attention focused on the screen, to make sure they are hitting the right buttons, the designers agreed.

Apple declined to make executives from its iPhone group available for this article, so it's hard to know exactly what was going through the company's mind. But the designers interviewed for this story think they have an idea.

"What has happened is that as the complexity of phones and the multidimensional capability of phones has increased, the ability to have an easy interface with them has become more challenging," said Bryce Rutter, co-founder and CEO of Metaphase Design Group.

While all designers bemoaned the lack of physical buttons, they also said Apple's touch-screen approach is a breakthrough in terms of how people interact with their phones.

You don't need a button to move the screen on an iPhone. You just move the screen, dragging your finger across it to scroll around or zoom in and out. "Touch introduces all sorts of compromises, but you can directly interact with the screen," Rolston said.

One of those compromises is the need to use two hands to properly operate an iPhone. "Some fundamental ergonomic principles come at the cost of really cool-looking design," Rutter said.

Physical buttons would have required Apple to make compromises on the size and quality of the screen, and would take away some of the flexibility of the iPhone. Buttons drawn by software can be discarded when the user switches to another application, but on other smart phones, a healthy portion of the device is covered with buttons that only come into play when typing.

So, is this a problem for Apple? Will users be frustrated by the need to keep two hands on their iPhones at all times? Perhaps at first, but there are some likely outcomes.

The first is that people simply adapt their behavior. Phones without QWERTY keypads didn't stop determined teenagers from text-based communication, the teens just invented an entirely new language to get around the fact that typing on a numerical keypad is hard, Rutter said.

And some of the main selling points of the iPhone are the other applications, where the one-handed usage model isn't as defined, Amit said.

The iPhone is also a media player, certainly the best video player that Apple has ever made, with its large screen and the ability to watch videos in landscape mode. And, "it's the first phone where I could say the Web is really working," he said.

But in the long run, the designers think Apple might have to introduce at least some aspects from the one-handed school of thought to capture a wide swath of the market.

"Being able to engage an iPhone at a restaurant without looking like a total idiot is really important," Rolston said. "You have to sneak it under the table, which requires a higher target precision. That's probably the battleground, the high context that a touch screen offers you versus the reliable precision of the full keypad."

There are a few ways the company might consider accommodating the one-handers. Apple could possibly make things easier for iPhone users through software updates, said Wai-Loong Lim, principal of Y Studios. "Everything on the screen is virtual. They might be able to redesign the interface for you to use just one hand, or even configure it if you're left-handed or right-handed."

Apple might consider backtracking on its no-buttons approach with the addition of a few customisable buttons on the side or base of the iPhone that users could assign to whatever tasks they choose. Or, future iPhones could also adapt the slider design used by Nokia and Helio on their smart phones, keeping the overall design aesthetic of the iPhone intact by hiding those uncouth buttons until they are needed. But Rutter isn't convinced Apple will change anything. "I don't think they are going to have to go back and 'fix it.' I think there will be a sufficient portion of the population that will make compromises."

Apple, of course, is known for thinking differently from many of its counterparts in the consumer electronics world about design, function and style. And by turning its back on years of smart-phone design, it's going out on that limb once again.

Not all of Apple's daring designs broke through to the public. Witness the Lisa, the Newton, the Cube and even the Mac Mini. But it's easier now for Apple to take design risks than perhaps at any other point in the company's history, as the success of the iPod and the growing use of Macs has established Apple's brand beyond its famous core of loyalists.

"Having a solid brand and an almost cult-like following grants you license from a design standpoint to push much further," Rutter said. "They are much more exploratory than a traditional electronics manufacturer that really doesn't have that license to push it out there."