My husband, Tom, and I have a series of hand signals that we use when we’re out together. When I shoot him a meaningful look and stroke my chin, that means “I have a piece of good gossip for you.” A discreet tug to my left earlobe means “time to go.” (Although, now that I’ve given it away, this gesture will be retired.)

Secret signals might sound like something from middle school. But they’re also fun.

When you’re an adult, playfulness may not always feel natural. But play helps you cope with stress and increases your life satisfaction. It also helps people in relationships feel closer. Playful behaviors like humor, banter or flirting can also remind you of the early days of your relationship, said John Kim and Vanessa Bennett, a therapist couple who wrote “It’s Not Me, It’s You.”

But playful relationships don’t always happen organically, said Roslyn Ashford, a licensed professional counselor in Mississippi. You have to invent or search for these moments of fun, she added. Here’s how.

Cultivate inside jokes.

Research has confirmed what we intuitively know: Humor is a key element of adult play. So look for small opportunities to add a little levity throughout the day, said Gaya Kodiyalam, a therapist in New York City.

You can cultivate your own lighthearted language, Kodiyalam said. She and her husband have so many nicknames for each other, she said, they rarely call each other by their given names.

They’ve also developed a series of funny rituals. The couple have a special morning hug they call a “waggle.”

These words and habits, “really do build intimacy,” she said.

Gags are another way to build in a bit of fun. For years, Tom and I had a running joke involving Baby Doll, a plastic infant our daughter had covered with magic marker tattoos. Over the years, Baby Doll had grown a grimy and sinister look.

So I would position Baby Doll in various poses — in the fridge, in the shower — to give Tom a scare. Immature, I know. But fun.

Send a silly text.

Dr. Ashford and her partner would text memes and emojis to each other for a laugh, she said.

I told Dr. Ashford that I sometimes try to find the most obscure emojis to send to Tom, without comment, like a lobster or a CD.

Or instead of texting in sentences, Dr. Ashford said, “you could speak only in emoji language,” and have your partner unravel your cryptic message.

A friend of mine texts his husband, who is frequently out of town for work, goofy pictures of their dog to make him laugh. Sometimes it’s a close-up photo of the dog huffing her food; other times he would draw on a jaunty hat or kerchief.

Plan a surprise date.

Kim and Bennett like to take turns devising a mystery date. One person does all the planning, “and all the other has to do is show up,” Kim said. Their dates have included rock climbing and renting a convertible for a scenic drive.

A good source of date ideas, Bennett said, is Airbnb Experiences, inventive activities led by local experts — many of which are not expensive.

The person being surprised should have an open mind and a good attitude, Bennett added. And if the date doesn’t go as planned, you have another inside joke, she said.

Kodiyalam encourages couples in her practice to think of activities that made them feel most alive when they were younger — and figure out how to do “an updated version of it.”

One couple she treated reminisced about scavenger hunts and obstacle courses, so Kodiyalam suggested they try tackling an escape room together. If you both loved to paint as children, you can try a “paint and sip” art class.

Make a game out of a mundane situation.

Add a little lightness to your day by looking for ways you can turn household tasks into a game, Kodiyalam said. You can have a contest to see who can make the most creative dish using ingredients you already have in the fridge or pantry, or who can tidy up an area in your house the fastest.

On a recent slog to the supermarket with Tom, I divided our shopping list and told him that whoever finished first would get a $5 scratch-off card. Lottery tickets don’t inspire the same greed in him that they do in me, but Tom loves a challenge. He raced through the supermarket aisles like a grim-faced action hero, winning the game.

Tom ended up giving the scratcher to me. I won $10. Which I then gave to him.