“She’s such a mama’s girl,” Deni said of Cali the other day. “If we get too far ahead, she looks back and wants to stop and wait for you.”

“Nah,” I said. “She knows that I have her precious tennis ball, and she’s worried that she won’t have it when she gets to the park.”

I may be a bit too cynical, and I do know that Cali and I have a close bond, but … when it comes to morning play, I really am just the tennis-ball carrier and tennis-ball thrower.

We tested our competing theories the next morning. As Deni, Cali and Alberta set off at a brisk pace, leaving Jana and me plodding at 12-year-old-golden speed, Cali glanced back once, then marched off, tail wagging. A key difference from the previous morning: Deni was wearing the all-important black backpack with Cali’s filthy, spit-coated, utterly disgusting tennis ball — the only one that Cali wants to play with.

Soon they were out of sight. When I got to the park with Jana, I asked Deni what had happened.

“Well,” she said. “Cali did look back twice, but she did not want to stop or even slow down.”

I knew it. Tennis-ball carrier status confirmed.

As I have mentioned before, play is very important to Cali and a huge part of our daily routine. She’s a very fair and friendly dog, and makes every effort to include all the humans present in whatever game is going on. When we’re not playing, she thinks that we should be.

In fact, Cali is my best balanced-life coach, nudging me at regular intervals to gently point out that it is time to take a break from this horrid computer, go outside, and play with her. And that darned tennis ball.

Cali knows what dogs have known for thousands of years and what has contributed significantly to the human-canine partnership: People and dogs play well together. Play makes all of our lives better. And playing with ours dogs makes our relationships with them better. According to a recent study by dog expert John Bradshaw, dogs who have frequent, positive play sessions with their owners (no scolding!) are more obedient and more engaged with their humans.

So, what are you waiting for? Get out there and throw that (disgusting) tennis ball!