Excerpt: 'The Secret of Play'

One heartwarming aspect of your child's behavior in the friendship arena is how easily and enthusiastically she makes friends. Within minutes of arriving at the playground, your child will be collaborating on a track for her new friend's plastic horse or marching happily arm and arm over to the slide. In contrast to unfamiliar adults at a dinner party, threes rarely engage in stilted small talk; they get right down to the business of having fun. (Interestingly, your child may do this even if she tends to be slow to warm up with adults.)

Why it's happening
Your preschooler is a better playmate because she's developing skills like taking turns and sharing. Her ability to delay gratification will develop further over the next few years—but she is starting to understand the give and take that relationships require. By her half birthday, it will probably be easier to wait her turn for the swing or for her chance to wear her friend's fairy crown.

Your child's problem-solving skills make it easier for her to resolve conflicts and to coordinate her play with her friends. For example, a young preschooler may still grab a toy, but when her friend then refuses to play with her, she learns to use a different approach.

Some 3-year-olds have an easier time than others when it comes to reading social cues. Depending on your child's temperament, she may be more sensitive to rejection or have a low tolerance for frustration that will impact her ability to sustain extended playtimes. But most children this age discover the delight in joining their buddies in elaborate fantasy worlds. One friend may say, "Let's be airplanes" and another will immediately spread his wings. This pretend play is less choreographed than it will be next year when they may discuss where to go and what to do there, but it's clearly more fun than taking a solo flight.

Studies suggest that your preschooler will learn close to a dozen new words daily. And her expanded vocabulary results in better self-expression and comprehension. Combined with her enhanced imagination, her communication abilities will enable your child and her pals to talk more, make up stories, and tell each other jokes (with punch lines only a 3-year-old could love). And if the joke worked once, expect to hear it again and again. Just as adult relationships are often strengthened by "in" jokes or stories that bring back warm memories, preschoolers' bonds are forged by routines and games that become a predictable part of their time together. Now that they are capable of recalling past events, they will gravitate to activities they enjoyed before, so have familiar toys handy.

Another aspect of your 3-year-old's enhanced social skills is her ability to empathize with others. Unlike a year ago, she clearly perceives that her feelings are separate from those of others and vice versa. You'll be amazed (and proud) the first time you see your child comfort a friend who has fallen or dropped her ice cream cone on the floor. She may pat the friend on the shoulder, offering words of comfort, like "Don't cry" or exciting solutions: "Your mom can buy you another ice cream!"

Friends are also a big deal at this age because it's thrilling for your little one to see that there are people out there who speak her own language—literally. After all, there's nothing better than finding a companion who is your own size, loves dinosaurs and mud puddles, and finds potty talk hilarious.

How to have fun with it
This is the time to schedule playdates with friends—especially those that your child mentions often. Try to let the kids play on their own, rather than planning every activity or getting involved at the first sign of a disagreement. Not only is this more fun, but it teaches your child about friendship and forces her to problem-solve.

Since sharing may still be a challenge at this age, help sharpen your child's skills by playing basic board and card games that require taking turns and reciprocating. Choose one-of-a-kind items—like a favorite puzzle or the heart-shaped cookie cutter—and have her wait her turn while you use it. A simple game of catch can help boost her ability to delay gratification: Before you toss the ball back, count aloud together, increasing the waiting period just a little bit each time.

Your 3-year-old's advanced motor skills expand the kinds of games she can play with her pals. For example, they can race each other around the backyard, climb the jungle gym together and, later this year, kick a ball around.

Certain toys are ideal for pretending with a friend. With puppet stages and puppets, kids have to work together on their productions or take turns if one child is the audience while the other one performs. Cash-registers and shopping carts can be props in a pretend store; wooden or plastic food and paper "menus" are great for playing restaurant, and camping kits mean they can imagine themselves sleeping out under the stars. Crumple some orange and yellow tissue paper around a flashlight, and they can sit around their campfire for hours!