The gun in my basement.

I'm sorry, are you busy?

Information is no longer a scarce resource - attention is. David Rose, a Cambridge, Mass.-based expert on computer interfaces, likes to point out that 20 years ago, an office worker had only two types of communication technology: a phone, which required an instant answer, and postal mail, which took days. "Now we have dozens of possibilities between those poles," Rose says. How fast are you supposed to reply to an e-mail message? Or an instant message?

Computer-based interruptions fall into a sort of Heisenbergian uncertainty trap: it is difficult to know whether an e-mail message is worth interrupting your work for unless you open and read it - at which point you have, of course, interrupted yourself. Our software tools were essentially designed to compete with one another for our attention, like needy toddlers.

The upshot is something that Linda Stone, a software executive who has worked for both Apple and Microsoft, calls "continuous partial attention": we are so busy keeping tabs on everything that we never focus on anything. This can actually be a positive feeling, inasmuch as the constant pinging makes us feel needed and desired. The reason many interruptions seem impossible to ignore is that they are about relationships - someone, or something, is calling out to us. It is why we have such complex emotions about the chaos of the modern office, feeling alternately drained by its demands and exhilarated when we successfully surf the flood.

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