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Blog · 18 April 2026 · 4 min read Brain

Three balls, three months

What the research on juggling and grey matter actually says - and what it doesn't.

Glowing red brain surrounded by juggling balls tracing an infinity loop

The most cited fact about juggling and the brain comes from a 2004 Nature paper by Draganski et al. The often-paraphrased version goes something like: “juggling makes your brain bigger.” That’s not quite what the paper says.

What it actually says is that adults who learned a basic three-ball cascade over three months showed grey-matter increases in specific motion-processing regions - and that those increases regressed when practice stopped. The mechanism isn’t growth; it’s structural plasticity in response to a sustained new demand.

2004
Draganski et al.
published in Nature
3mo
Practice period
to produce measurable grey-matter change
↓
Regresses
when practice stops
2
Brain regions
motion-processing areas affected

Two things follow from that:

  1. The benefit is real but not permanent. Three months on the mat earns you a measurable change. Three months off the mat takes it back.
  2. The brain region matters. Don’t expect juggling to make you better at crossword puzzles. Expect it to make you better at things that share substrate with juggling - tracking moving objects, fast motor planning, incremental skill acquisition.
grey matter densitybaseline3 months practice3 months restendpeak increasepractice phaseregression
Structural plasticity in response to demand: grey matter increases during the practice period, then regresses during rest. The brain responds to current demand - not to past effort.

The mechanism isn’t growth. It’s structural plasticity in response to a sustained new demand. Stop the demand, and the structure returns toward baseline.

The longer essay is over in Ideas.

Further reading

  • Draganski, B., Gaser, C., Busch, V., Schuierer, G., Bogdahn, U., and May, A. (2004). “Neuroplasticity: Changes in grey matter induced by training.” Nature, 427(6972), 311-312. The primary study. Available via DOI: 10.1038/nature02187. The three-month protocol and the specific brain regions affected are detailed here.
  • Driemeyer, J., Boyke, J., Gaser, C., Buchel, C., and May, A. (2008). “Changes in gray matter induced by learning - revisited.” PLOS ONE, 3(7). The follow-up: grey matter changes begin within 7 days of starting practice, and the reversal rate after stopping correlates with practice frequency.
  • Scholz, J., Klein, M.C., Behrens, T.E.J., and Johansen-Berg, H. (2009). “Training induces changes in white-matter architecture.” Nature Neuroscience, 12, 1370-1371. The companion finding: juggling also changes white matter connectivity in the visual-motor pathways, not just grey matter density.

Related: The Gift of Beginning - on what happens in the brain from the very first throw. The Loop That Rewires You - on myelination, the structural mechanism behind skill acquisition. What Actually Happens in Your Brain When You Juggle - the full detailed analysis of the Draganski paper and what it does and does not show. Juggling in Science and Public Life - the Draganski study in its historical and scientific context.