Cell phones and PDAs have become so indispensable to many people that they show up as uninvited guests at everything from movies to funerals.

This year when families set the table for holiday feasting, they may need to leave extra space beside the candy bowls.

Cell phones and PDAs have become so indispensable to many people that they show up as uninvited guests at everything from movies to funerals.

Obviously, these devices have their place. They've made communication quick, reliable and even fun. That's why the typical American teen sends 3,000 text messages each month. Yet without boundaries, the constant chatter from electronic devices can interfere with your child's ability to focus and your family's opportunities to connect.

Although teens and many adults have adopted multi-tasking as a way of life, brain research suggests that constantly switching from one activity to the next interferes with short-term memory and long-term learning. Being able to decide where you'll focus your attention turns out to be a rather strong predictor of success in a variety of areas.

In one fascinating study, a researcher left 4-year-olds alone in a room with marshmallows. The kids were told they could have a second marshmallow if they didn't eat the first one. Many of the kids succumbed and popped the marshmallow in their mouths.

Some, however, didn't - largely because they were about to focus their attention on something other than the marshmallow. Years later, the kids with the ability to control their focus were getting better grades and higher SAT scores.

Teaching kids to screen out electronic distraction - or marshmallows - isn't easy, but the holidays are a good time to start. Parents must lead by example. Demonstrate your priorities by locking away your own electronic devices during special meals and other holiday festivities. (It's not okay to keep your PDA in your pocket or your lap "just in case.")

If you really believe the messages you're missing could be urgent, keep a log. Then, one by one, rate the importance of the communication against the importance of what it interrupted. If something is truly an emergency that requires your attention, excuse yourself with apologies just as you would if you had to take a phone call.

Once you've demonstrated that texting and other forms of electronic communication can be put in their place, you're more likely to get through to your kids about keeping their own habits under control. Here are some instances in which you should be especially firm:

The facts are in. Driving while texting is like driving buzzed. Even talking on a cell phone impairs the split-second reactions that can help drivers avoid accidents. Make a family resolution: NO ONE in your family will text while driving.

To enforce the rule, turn phones off in the car so no one is tempted to respond to that seductive ring tone. Don't call your teen if you think he or she might be driving. And make it a rule that anyone who needs a phone fix will pull over and park.

Being able to talk to people face to face continues to be a valuable skill, but parents have to work hard to cultivate it, especially in text-addicted teens. Genuine conversation requires attentive listening, something that won't happen if electronic devices are buzzing and blinking. Holiday dinners are one place to start.

Encourage everyone to leave automatic messages making it clear to callers they don't want to be disturbed. If your kids protest, point out that knowing how to focus on the person in front of you is a huge advantage in romantic relationships. Parents also should remember that nothing is sexier than giving your partner your undivided attention.

Research from the National Institutes of Health provides decisive evidence that teenagers need about nine hours of sleep a night. One recent study found that teens who routinely stayed up until midnight on school nights were more likely to be depressed or even suicidal. Of course, even if your teen doesn't send messages after the lights are out, other kids may not have the same restraint.

Use the phone bill to monitor the hours when your child's phone is being used. Then encourage your child to establish black-out times with friends. If kids can't enforce the rule, confiscate phones at bedtime.

Sherry Turkle, one of the first researchers to examine the psychological impact of the digital revolution, believes it's become more difficult for young people to find the peace and quiet they need to think their own thoughts. A device that vibrates every few minutes produces a sense of urgency. Kids feel they have to respond and some young people report that their friends get angry with them if they aren't instantly available.

Parents owe it to their kids to help them carve out genuinely private time. In some households, this means parents themselves have to use restraint. Electronic devices allow parents to be in constant contact with kids which may make it more difficult for kids to learn how to make their own decisions and solve their own problems. Just because you can text your child doesn't mean you should.

In each of these cases, the goal is to teach children that like time and money, attention is a resource that shouldn't be squandered. The holidays are an especially good time for everyone to remember that in our distraction-filled world, giving someone your undiluted attention may be the best gift of all.