What’s your one?

Simplicity, honest info and our own experience

I’m going to try to convince you about simplicity in product design over the next months.

Let’s start here:

If you could define yourself only by one number. One number that you can easily measure. What would it be?

I got to thinking about this when a friend recently said that her Spotify listening age was 21. And she is rather well over 21. She didn’t seem too sure if that was a good thing. Spotify added this measure to the 2025 Wrapped subscriber email¹. It gained a lot of social media attention. The most positive emotion seemed to come from people whose listening age was decades older. Perhaps signaled strong, deep music knowledge. Anyway, if you are young, might you need to play music like “Baby Shark” to be calculated as listening even younger?

Then there is health. My fitness club provides an excellent data system and app. A few months ago, I started working out on their “egym” circuit. Love it. Although I have really smiled at the app: it shows my strength age, which at the start was a couple of years older than my chronological age. Of course, I didn’t like that. Now it moves down a couple of years regularly. Figure by the end of the summer I’ll be two decades younger. Maybe by year-end back to 20!

Just because we can measure it, do we need it?

A recent Wall Street Journal (WSJ) article compared fitness trackers – Oura Ring 5, Google Fitbit Air, Whoop MG, and Apple Watch Series 11.² As personal tech columnist Nicole Ngyyen points out at the start, “Studies show that tracking activity does spur people to move more. But the data influx can create excessive worry or an unhealthy obsession with achieving perfect scores.”

Is this really a good thing?

We are now measuring the calculated age of many parts of our (bodies and) lives: epigenetic / DNA methylation age, heart age, brain age, organ-specific ages.

George Miller – the American cognitive psychologist who cofounded the field of research – famously published that our working memory holds roughly seven items (plus or minus two).³ That we risk cognitive overload with more. Add to that the research of German cognitive psychologist Gerd Gigerenzer, who points out that too much medical data can actually cause less accurate diagnosis by both patients and medical professionals.⁴

We need frameworks, systems and models to simplify the view.

What number matters most?

Of course at times of transition, additional or new measures can be helpful to focus on and create a new habit. Yet simplicity suggests that we only need a few to do that. Minimum info in an honest form.

Which got me to thinking, my most honest form does not always need a piece of data.

More than my strength age, I follow how my clothes fit. For sleep, I have a few fundamentals: be relaxed at bedtime, drink little caffeine, exercise, and watch the wine. I don’t need a sleep tracker to tell me when I have broken one of them.

These are what Gigerenzer would call my “rules of thumb,” developed based on a look at the honest information, combined with real life experience.

Nugyen concluded in her WSJ tracker testing that the devices are often accurate and interesting, “Yet no matter how smart and capable they’ve become, they still can’t replace my own body’s intuition.”

Let’s take that now to design, where we will pick up again later. Antoine de Saint-Exupéry, the French poet and aviator wrote, “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away.”⁵ The beauty of living lies in its bare essentials.

Keeping it simple shows understanding of us as humans. It recognizes intuition and does not waste our energy needing to interpret and evaluate what we already know through honest information and experience.

Tools like fitness trackers can serve us rather than define us. One or two numbers – or perhaps even better, rules of thumb – will do.

NOTES

1 Spotify is reported to have added Listening Age to its annual wrap-up subscriber email in 2025 to serve especially Gen Z and Gen Alpha, which tend to listen more across genres and decades. Here is a fun Rolling Stone look at how Spotify calculated Listening Age and the social media frenzy that followed.

2 Wall Street Journal, 7 June 2026. The Wearable Showdown: Oura Ring 5 vs. Fitbit Air vs. Whoop MG vs. Apple Watch. Enjoyable article in which Nicole Nguyen reports on her three-week comparative test of sleep and heart rate monitoring.

3 George Miller was one of the original founders of the field of cognitive science. Researching mental processes like memory, language, and perception. Biography on Wikipedia.

4 Gerd Gigerenzer argues that simple heuristics (i.e. mental shortcuts – “rules of thumb”) are often well adapted to real-world environments and frequently superior to complex statistical models because of their simplicity. Biography on Wikipedia.

5 Antoine de Saint-Exupéry (1900–1944) was a French author, poet, and pioneering aviator. Quote above attributed to his book Wind, Sand and Stars (Terre des Hommes, 1939), a memoir about flying and human solidarity, winner of the Grand Prix du Roman of the Académie Française and the U.S. National Book Award. Saint-Exupéry’s book The Little Prince (1943) is one of the best-selling books in history. A children’s fable about a prince from a tiny asteroid. Biography on Wikipedia.

Research aided by Claude.ai (Sonnet 4.6).

No AI used for writing, except occasional exploration of specific word choices.