Psychotherapy’s Taxonomy Problem

Why We Keep Arguing About Mythical Animals Instead of Studying Behavior

Imagine walking into a county fair where the grand prize is about to be awarded for Best Animal. One contestant is an elephant with zebra legs, butterfly wings, peacock feathers, and octopus tentacles. The next is a giraffe with the body of a bear, tiger paws, and the tail of a fish.The judges are having an intense argument.

Which creature is more authentic? Which one has the better anatomy? Which one deserves the blue ribbon for Effective Treatment?

No one stops to ask a more fundamental question.

When did we stop studying animals and start arguing about mythical ones?

Sometimes I wonder whether psychotherapy has wandered into the same county fair.

Every generation of researchers tries to build a better way of understanding human suffering. That’s exactly what science should do. New theories propose new mechanisms. New measures. New therapeutic languages. New ways of organizing behavior.

Over time, though, something subtle happens.

We stop treating those theories as useful maps and begin treating them as though they were different species inhabiting nature.

ACT becomes one animal.

CBT becomes another.

Psychodynamic therapy, DBT, Process-Based Therapy, Unified Protocols—they each develop their own anatomy, their own vocabulary, and their own criteria for what healthy functioning looks like.

Then the debates begin.

One of the most common arguments is that comparing therapies like ACT and CBT is like comparing apples and oranges.

I think we’ve accepted the wrong conclusion.

Apples and oranges are remarkably easy to compare.

We compare them by properties they both possess: acidity, water content, sugar, fiber, weight, shelf life.

What we don’t do is ask whether the orange became a better apple.

Yet that’s surprisingly close to how psychotherapy research often operates.

Each theory develops its own mechanisms.

Its own process measures.

Its own language.

Its own explanations.

Then we ask whether each therapy became a better version of itself.

The more our theories evolve, the stranger the animals become.

New mechanisms are added.

Old concepts are borrowed.

Measures are refined.

Constructs multiply.

Eventually we’re no longer comparing elephants and giraffes.

We’re comparing beautifully assembled mythical creatures built from decades of accumulated assumptions.

Then we race them.

We hand out blue ribbons.

And we argue endlessly about which mythical animal won.

I don’t think this is because psychotherapy research is failing.

I think it’s because our theories have become more sophisticated than the way we measure them.

Karl Popper reminded scientists that observations are never interpreted in isolation. Every scientific test rests on a network of assumptions connecting theory to observation. The challenge is not pretending those assumptions don’t exist; it’s remembering that they’re there.

Perhaps psychotherapy has become so successful at building increasingly sophisticated theories that we’ve started mistaking the theories for the thing they were created to explain.

The thing we were trying to understand was never ACT.

Or CBT.

Or any other named therapy.

It was human behavior.

Maybe the next step in psychotherapy isn’t inventing another mythical animal.

Maybe it’s learning how to measure the behavioral dimensions that all of them have in common.

Because mature sciences don’t advance by becoming more loyal to their taxonomies.

They advance by discovering ways to build knowledge across them.