On the walk back down the driveway after getting the newspaper, I notice a soft, brown clump prominently visible on the gravel. Of course, I have to find out who made that scat. I turn to my official scat identification guide:

Is the scat round? No. My medical training in differential diagnosis kicks into gear. Not round. That rules out rabbits.

Is it round and elongated? Not really. That rules out squirrels and mice, who make small, elongated spheres, and deer and moose, who make large elongated spheres.

Now we come to cylinders. Yes, it is cylindrical. Are they broken cylinders? No. Turns out that, according to my scat guide, broken cylinders are usually from members of the cat family, including pet cats and bobcats.

How about pointed on the ends? Yes! Who knew that cylinders with pointed ends are often from members of the dog family, including pet dogs, coyotes, and foxes.

The scat was smaller and pointier than my neighbor’s dog produced. To my relief, pointy-ended cylinders rule out bears, who make large, blunt cylinders.

Now for the pathognomic feature — this is a medical term that means a symptom or sign that points to the exact diagnosis. In this case, the unique feature was whether the scat had a strong, offensive odor, which would confirm definitively that this pile was red fox-generated.

I confess that I did not lean in enough to catch a good whiff, but even without that sure sign, this scat appeared to have been produced by a red fox. Supporting this conclusion is the fact that I had seen a red fox sprint across the yard numerous times in past weeks.

 My neighbor’s toddler has been focused on scat, or poop, as he calls it, for the past few weeks, not so much for its appearance, but rather, for its intended location. Can he get his poop into the potty?

Whoever left their scat in my driveway at will is certainly envied by this small boy. The child had been nervously and, at times, frantically asking to return to a diaper for a few days before finally taking a seat on the potty.

“I did it!” he cried when he accomplished the task. His parents beamed. Renowned psychologist Erik Erikson, a contemporary of Freud, would have joined the celebration, recognizing this as an important developmental milestone.

Erikson would describe this child’s accomplishment as reflecting mastery of the developmental stage of ‘autonomy,’ or self-determination, referring to having some control over one’s bodily functions.

Psychological development doesn’t stop at toddlerhood. Just as an acorn holds within itself all the steps to becoming a great oak tree, a human being contains the template for eight stages of development, which continues all the way into old age, according to Erikson.

Another stage, for example: During adolescence, the focus is on ‘identity,’ discovering one’s identity and developing the ability to sustain a coherent sense of self in different domains of one’s life.

Between the ages of roughly 25 and 65, different for each person, our innate challenge is “generativity,” addressing how to guide and contribute to future generations and to the future of the world, regardless of whether we have children.

As older adults, we face the daunting stage of “integrity,” the challenge of maintaining personal integrity in the face of loss and decline.

We are biologically pre-destined — dare I say, pre-programmed — to evolve psychologically, barring impediment. Somehow, when the time is right and with the right supports, we doff the diaper.

The red fox, similarly, intrinsically knows how to behave as a fox. Is this the lesson of the red fox, a testament to the natural developmental process built into an acorn, a fox, a little boy or girl?

Or perhaps I’m getting beyond myself: Perhaps this plop is just a scoop of scat.

Diane Roston, MD, is on the clinical faculty at the Geisel School of Medicine at Dartmouth and is a physician at West Central Behavioral Health in Lebanon.