Why we built it on pink noise

Our partners at the University of Nebraska Omaha just published a new paper in PNAS, and it gets at the idea that PinkSteady is built around. The paper is titled "Pink noise promotes sooner state transitions during bimanual coordination," and it was led by Kolby Brink with Aaron Likens and Nikolaos Stergiou, who runs the Center for Research in Human Movement Variability at UNO.

Here is the basic question they were asking. When people are doing a coordinated movement, like tapping their two index fingers in sync with a metronome, how does the variability of the metronome itself change their ability to shift smoothly between different patterns of coordination?

The metronome was tested in four flavors. First was a perfectly invariable beat. Then there were beats embedded with three different kinds of noise: white noise, which is the random hiss you hear between radio stations, brown noise, which is a slow drifting rumble like a low-frequency hum, and pink noise, which is the kind of variability you actually find in healthy biological systems, like the rhythm of a heartbeat or the pattern of a person's stride.

Pink noise was the winner. People synced to a pink-noise metronome made faster, smoother transitions between coordination patterns than people synced to any of the other conditions, and both the brain imaging and the computational simulations lined up with the behavior.

The takeaway is that "healthy variability" is not a contradiction in terms. The right kind of fluctuation in a movement signal does not destabilize you, it actually makes you more adaptable, more able to respond to whatever the world throws at you next.

This is the science PinkSteady is built around. Stability is not the absence of variability, it is the right kind of variability. When we score a steadiness check-in, we are not looking for someone to be perfectly still, we are looking for the texture of their movement to match the pattern of a healthy, adaptive system. That texture is what shifts in the months and years before a fall, and it is what we want to help families notice in time.

The full paper is on PNAS: Brink et al., PNAS 2024.