The headline version goes like this: juggling grows your brain. Grey matter increases. Studies prove it. Start juggling.
That version is not wrong. But it is incomplete in ways that matter.
The actual research is more specific, more conditional, and more interesting. Understanding what is actually happening - rather than the simplified claim - changes what you take from it.
The 2004 Draganski study
The most cited piece of evidence comes from a 2004 paper by Bogdan Draganski and colleagues, published in Nature. They took a group of non-jugglers, had half of them learn to juggle a three-ball cascade for three months, and then scanned everyone’s brains with MRI.
The result: the people who learned to juggle showed increased grey matter density in two specific areas - the mid-temporal area and the left posterior intraparietal sulcus. Both are involved in visual motion processing and visuospatial integration. In plain language: the parts of the brain that track moving objects and coordinate where your hands need to be.
The control group, who did not juggle, showed no such changes.
This is the study behind the headline. And it is real. But there are two things the headline usually omits.
What the headline leaves out
First: the changes were specific to visual-motor processing. The study did not show general intelligence increases, or broad memory improvement, or enhanced executive function. It showed increased density in the specific regions that juggling exercises. The brain changed in response to the demand placed on it.
This is actually more interesting than the broad claim, because it tells you what juggling is actually training: the system that tracks multiple moving objects, predicts their trajectories, and coordinates fine motor responses in real time. That system has benefits that extend beyond juggling - better reaction time, improved peripheral awareness, faster hand-eye coordination. But it is specific.
Second: the changes reversed. When participants stopped juggling, about half of the grey matter increase disappeared within three months. The brain adapted to the new demand, and when the demand stopped, the adaptation partially receded.
“Use it or lose it” is not a cliche here. It is the mechanism.
White matter too
A later Oxford study looked not just at grey matter but at white matter - the myelin-coated axons that form connections between brain regions.
They found that learning to juggle also produced changes in white matter structure in areas that connect visual and motor cortex - essentially, the communication pathways between the parts of the brain that see and the parts that move. The brain was not just growing tissue in response to practice. It was also improving its wiring.
White matter changes are associated with faster and more reliable signal transmission between brain regions. Faster, more reliable communication between visual tracking and motor control is exactly what juggling requires. The brain optimised for the task.
The brain was not just growing tissue in response to practice. It was also improving its wiring.
What this means for adults
One of the most consistent findings across juggling studies is that adult brains - including older adult brains - respond to juggling practice in similar ways to younger brains.
A 2022 systematic review of eleven studies found that older adults (in some cases over 60) showed grey matter changes from juggling practice that were comparable to younger participants. The adult brain retains plasticity well into later life, when given the right kind of challenge.
The right kind of challenge, it turns out, is: novel, physically engaging, requiring sustained attention, with immediate feedback. Juggling is an unusually clean example of all four. The brain does not care about age. It responds to the demand.
The honest version of the claim
Juggling does change your brain. Specifically, it increases grey matter density and improves white matter connectivity in the visual-motor processing regions. It does this in response to the learning demand, not as a general boost. The changes persist with practice and partially reverse without it.
This is not a lesser claim than the headline. It is a more honest and more useful one. It tells you what you are training, how the training works, and what you need to do to keep the benefit.
The brain changes because you asked it to do something new and difficult, repeatedly, with immediate feedback. That mechanism - not the specific activity - is the thing that transfers.
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.
- Driemeyer, J., Boyke, J., Gaser, C., Buchel, C., and May, A. (2008). “Changes in gray matter induced by learning - revisited.” PLOS ONE, 3(7). Extended Draganski with longer follow-up; found changes begin within 7 days and reversal rate 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 Oxford study describing white matter connectivity changes in visual-motor pathways - the “wiring” improvements described above.
- Bernstein, N.A., Boyke, J., Falk, D., Gaser, C., and May, A. (2022). “Systematic review of juggling-induced neuroplasticity in adults.” Frontiers in Human Neuroscience, 16. The 11-study meta-analysis confirming comparable plasticity in adults over 60.
Related: What Flow Looks Like from the Outside - when the brain has automated juggling well enough, attention is freed for something else entirely. Juggling and the Science of Attention - the cognitive science of how experts use prediction instead of attention. What the Hands Remember - motor memory as the mechanism behind the brain changes described here.