At their core, the iPhone and iPad are unitasking devices. While they technically allow several applications to run at the same time, one app owns the screen. More than one app may be running, but you’ll only ever see one at a time.

When people complain about the iPad or iPhone’s poor multitasking capabilities, a common response is that proper multitasking isn’t required, since people can’t multitask, either. By that reasoning, only being able to see a single app at a time is actually a good thing, since it helps people focus. For example, Jocelyn K. Glei writes:

The first-generation iPad has the unique benefit of being a beautiful device that forces you to uni-task. A recent WIRED article touted the tablet as a great learning device, commenting: «On the iPad, any application you run takes over the full screen. So, when you launch your note-taking app for class it’s the ONLY thing you see. It improves focus and makes it more difficult for our easily-distractable students and employees to browse away to Facebook.»

Similarly, Shawn Blanc notes:

I have never been frustrated by iPhone’s lack of «multitasking» and on the iPad I actually prefer to be restrained to one thing at a time. (It helps me focus and stuff.)

There is some truth to that idea. Humans can’t multitask. Summarizing research on the topic, the New York Times writes:

Several research reports, both recently published and not yet published, provide evidence of the limits of multitasking. The findings, according to neuroscientists, psychologists and management professors, suggest that many people would be wise to curb their multitasking behavior when working in an office, studying or driving a car. (…) «Multitasking is going to slow you down, increasing the chances of mistakes,» said David E. Meyer, a cognitive scientist and director of the Brain, Cognition and Action Laboratory at the University of Michigan. «Disruptions and interruptions are a bad deal from the standpoint of our ability to process information.» The human brain, with its hundred billion neurons and hundreds of trillions of synaptic connections, is a cognitive powerhouse in many ways. «But a core limitation is an inability to concentrate on two things at once,» said René Marois, a neuroscientist and director of the Human Information Processing Laboratory at Vanderbilt University.

Clearly, being forced to only see one app at a time can be beneficial. You won’t get distracted by Twitter as easily, for example.

However, the argument that multitasking on computers is bad because humans can’t multitask is flawed. It uses the word «multitasking» in two different ways, but implies that the two kinds of multitasking are somehow the same thing. They’re not: a task (or an app) on a computer, and a task performed by a human don’t map to each other one-to-one. In fact, a single task performed by a human can easily make use of several applications running concurrently on a computer.

For example, right now, I’m typing this text in Notational Velocity, and I’m looking at the New York Times article I quoted above. The computer is showing me two windows at the same time. It is multitasking. I, however, am not. I’m absolutely focused on writing this essay. In fact, the computer’s multitasking is precisely what allows me to focus on writing my essay. I can type text into this window while looking at the Times article in another window without being forced to interrupt my task, and consciously switch between apps.

Earlier today, I was writing an e-mail while referring to a conversation I had in Skype. Again, the computer was showing me two windows, but I wasn’t multitasking.

This afternoon, I spent a few hours making changes to an XML file in BBEdit while looking at comments an editor added to a PDF file. Again: two windows, one task.

The fact that the iPad only lets me see one app at a time often does not help me focus. Instead, it forces me to switch between apps constantly, thus preventing me from focusing on my task. Every time I have to deal with the iPad’s task switching, I’m interrupted.

For some tasks, letting applications take up the whole screen is useful. Applications like Garage Band or Writer make good use of the screen. But a lot of the time, allowing more than one app to occupy the screen can actually help people focus, because human tasks are often not as simple as computer tasks, and may require people to be able to see more than just a single application.