When the phone rings or a text comes in, the sound can be just as urgent as a lion in the brush — and just as tough to ignore. Is it your spouse? Your boss? A new business opportunity? Primitive brain wiring compels you to answer. But what if you’re driving, like Reggie?

Much of the information that comes through is insignificant, even a nuisance, like spam. Wouldn’t that cause people to learn to ignore it? Perversely, just the opposite is true. The fact that the information is of variable value actually increases its magnetism. That’s because it creates a lure called intermittent reinforcement, a powerful draw that comes with uncertainty of the reward. It’s the very thing that causes a rat in a cage to press a lever repeatedly when it isn’t sure which press will bring the next delivery of food. It presses again and again, just as we click to open our text or email programs.

“What’s happening, in essence, is that you’re constantly scanning your texts and email because every once in a while you are going to get a good one and you can’t predict when that is,” says David Greenfield, a psychologist and an assistant professor at the University of Connecticut School of Medicine, where he teaches a class on Internet addiction. He compares the Internet to a slot machine, adding: “That’s why Facebook is so popular. It’s the fact that it’s dynamic and novel, and constantly changing.”

The idea that technology use affects the brain is supported by a growing body of neuroscience. Several studies show that when people play video games or use the Internet, they exhibit changes in the levels of dopamine, a neurochemical associated with pleasure, similar to changes in the brains of drug addicts. When you hit “send” or press a letter on the keyboard, it prompts a change on the screen, a picture pops up or an email opens, and you get a little dopamine squirt, Dr. Greenfield says, a kind of adrenaline rush. If you do it over and over, it conditions you to the rush, and in its absence you feel bored.

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“It’s in a sense a narcotic,” he says.

That doesn’t mean that electronic devices are classically addictive; instead, many researchers say that these devices have addictive properties and are habit-forming, but that more research is needed before deeming them addictive in the way that drugs, say, can be. There is wider agreement among scientists that the risks are higher for young people, whose frontal lobes are less developed and therefore even less able to fend off the ping of the phone delivered from the more primitive part of the brain.

But even for adults, the devices appeal to such primal social urges that they can be overpowering.

“The cellphone, and other similar technology, meet a deep need for social connection with a greater ease and greater potential detriment to it in the same way that a vending machine that is right down the hall plays to our need for calories,” says Dr. Nicholas A. Christakis, a physician and a professor of social and natural science at Yale; he is an expert in the use of social networks across time.