Food, water, shelter -- and cellphones?
Americans are so attached to the little gadgets that 29 percent of cellphone owners say they couldn't imagine living without them, according to a recent study by the Pew Internet and American Life project.
Among smartphone owners -- nearly half of American adults -- the dependence is even greater, with 36 percent viewing the gadgets as key to their existence.
But they also worry about being a bit too plugged-in.
"They appreciate what [phones] can do in helping them navigate their daily lives," said Aaron Smith, a Pew researcher. "But they also bring a certain amount of stress and anxiety."
About a quarter of those surveyed said they dislike being reachable at all times, and 39 percent said they've heard complaints from others when they don't immediately respond to calls and text messages.
Maybe that's why 67 percent of adults surveyed said they check for messages or calls even when their phones aren't ringing or vibrating.
Forty-four percent said they had slept with the cellphone next to the bed to avoid missing calls, texts or late-night updates.
Most habits were similar among users of all sorts of smartphones, but iPhone users -- who are more likely to use the devices to play games -- worried a bit more than Android phone owners about spending too much time with their phones, Smith said.
"We may be picking up on residual angst about how much 'Angry Birds' or 'Fruit Ninja' people are playing," he said.