• This seems to me to be a metaphor rather than an analysis, depending on "multitasking" and "divided attention" being synonyms. Multitasking is a term of art in computer engineering, denoting the activity of using a computer to run multiple tasks "at once," by timeslicing and context-switching. These are just words that mean running a program for an instant, saving everything about the task's current execution environment and running another program for an instant, with some provision that a task that needs to give urgent attention to a signal arriving from outside the system or from another program can "pre-empt" the routine of task dispatching to get control immediately.

• This is not how human brains work, no matter who is using them and how. Human brains are immensely parallel processors of information, clusters of activity performing different tasks on different time scales in uncoordinated ways, sharing vast flows of information back and forth between parts over very dense fiber links specialized for carrying all those signals in precise time structures, compensating for the fact that different systems work at different speeds to create a synthetic relation among signals that we call "now."

• "Attention" is one aspect of human mental function, a subsystem of consciousness. It prioritizes signals from sensory systems, coordinating results, for example, of lengthy and somewhat slow fine visual processing with much faster auditory processing to synchronize experiences of sounds and sights happening "together," as when we watch a musical performance and pay "attention" to different parts of our surroundings from second to second. Attention doesn't "multitask," it coordinates the arrangement and processing of multiple simultaneous cognitive and interpretive streams.

There is increasing evidence that multitasking amounts to chronic distraction, which comes with an attendant list of mental disadvantages. Some educators claim that heavy multitaskers won't do as well in school. While they say that the younger generation of multitaskers are much better at understanding and incorporating visual data, their writing skills have deteriorated. As people pack more and more hours of media content into the day, there is less time for reflection. As a recent writer in The Atlantic lamented, chronic multitasking has made less and less time available for deep thinking.

• That's not a statement about multitasking or about attention. That's about the loss of interiority, partly as a result of limited "time available" for contemplation, but more about the fact that continuous communicative contact with others results in a suspension of the "interior self." Change of society, going from, say, Iceland to India would do the same thing without any technological assistance. But the persistent change in level of interiority in a society, which is currently going on in the US as a generally less interiorist generation grows up, is causing people to assume the sky is falling, as you are doing here. The Atlantic, which is the middlebrow home of the interiority set, or perhaps is right behind Psychology Today and the New York Review of Books, is precisely where the deploring should be most thoroughly going on.

There are plenty of anecdotes from people who claim that it is much harder to read a book now than it was before they became enmeshed in the internet, and a recently published study of online research habits shows that most people only skim online articles, frequently bounce around to new media, and rarely return to finish the original. Most multitasking involves social networking, like email, instant messaging, and Facebook. The constant interruption, much of it stimulating the reward pathway in the brain, leads to a climate of chronic distraction. Just as reading is a learned skill, the kind of chronic multitasking that many users engage in may be reprogramming the brain, rewiring it to prefer skimming at the expense of deep reading. The loss of the ability to read deeply may be synonymous with the loss of the ability to think deeply. There is even some evidence that people in chronically distracted jobs are, in early middle age, appearing with the same symptoms of burn-out as air traffic controllers.

Not all kinds of multitasking are the same. Highly practiced skills, like chopping an onion, can be performed while still having an engrossing conversation, but two complex activities are almost invariably performed sequentially rather than in parallel.

• If they are of similar type. Listening to something engrossing while doing fine hand-eye coordination work of a different kind does not produce interference, as everyone from jewelers to graphic designers to brain surgeons will tell you. But talking on the telephone interferes with driving. And hearing the same thing you are reading interferes with comprehension, too, even though "multitasking" is not involved.

• That's a great deal to conclude from one study of a few people.

• Yes, but there's no agreement whatever on the phenomenon. That stress causes fatigue was observed sometime around the end of the last Ice Age.

This climate of chronic distraction is easily exploited by commercial interests looking to find eyeballs. As heavy multitaskers continue to use the meta-medium of the web, it becomes increasingly difficult to tune out possible distractions.

• This isn't necessarily true. Heavy web users, like library researchers for example, know that speed and productivity can be increased by using text-based browsers and depleted interfaces. Hence, for example, the tool called Surfraw. Improvements to the browser that use it for something other than eyeballing, like Zotero, also reduce the division of attention for serious users of the web. But most importantly, your concern about distraction emerges largely from the competition for attention that results when the web has advertising on it. The step of removing advertising so profoundly changes the experience of the web that discussion of its cognitive effects has to begin again from the basics. Everyone can remove all advertising from the web immediately.

This works in the favor of those seeking to capture attention, however transient, from users. It becomes relatively easy to shuttle viewers, once captured, to new media in their endless search for novelty. Once novelty-seeking behavior becomes ingrained, targeted ads are almost assuredly brought into the mind's scatterbrained eye. Human freedom ends up curtailed as users are tempted into buying products they don't need, or are shunted down a path of media consumption unintended by the volitional mind.

• Whether this is a conclusion or not, it certainly reinforces the impression that the whole essay depends on the advertising. Why don't you install AdBlock? in your copy of Firefox and see what happens to the whole argument after a little while.