Draganski 2004: What Learning to Juggle Did to Gray Matter

Twelve volunteers learned to keep three balls in a cascade going for 60 seconds, and 12 others did not learn at all. Draganski et al. (2004, Nature 427:311-312) scanned everyone before practice, after three months of it, and three months after the jugglers stopped.

So does learning to juggle grow your brain? In a narrow, measurable sense, yes: the jugglers showed expansion of gray matter in the mid-temporal area (hMT/V5) and the left posterior intraparietal sulcus, both involved in processing moving objects, and the controls showed no change. The expansion partly receded once practice stopped. That is all the paper claims, and it is a result about structural MRI, not about intelligence, mood or excitement.

What did the follow-ups find?

Driemeyer et al. (2008, PLoS ONE 3(7): e2669) repeated the design with 20 adults and six scans. Gray matter rose in hMT/V5 on both sides (right Z = 4.56, left Z = 3.25, uncorrected), and the increases reversed in the scans taken after practice stopped. The paper reports a parietal peak too, but only the hMT/V5 result is presented as a replication.

Boyke et al. (2008, Journal of Neuroscience) taught juggling to older adults, averaging about 60. They learned it less well than 20-year-olds, yet showed gray-matter change in the same visual area, plus transient increases in the left hippocampus and the nucleus accumbens.

How strong is the evidence?

Weaker than the headline. Thomas and Baker (2013, NeuroImage 73:225-236) reviewed training studies and concluded that design limits, statistics and methodological artifacts may explain many reported effects. The strongest case they found was hippocampal change after exercise in older adults, not skill learning. R. Douglas Fields, replying, argued that their review leaned on a vote-count and one negative study.

A single fact shows why caution is warranted. Driemeyer found no significant link between the size of the change and how well people juggled or how many hours they practiced. Their own reading was that learning something new matters more than repeating it. “Gray matter volume” also does not mean more neurons, and a bigger region is not a better brain.

Why pick a pointless skill with a friend?

Nothing above says juggling makes a week feel less flat. That is my inference from a different angle. A new skill gives you something to be bad at, which breaks up a routine week. Self-expansion theory found that couples who did a novel, arousing task together reported bigger gains in relationship quality than couples who did a mundane one (Aron et al. 2000), though that tested couples, not friends. The wobble before competence is real, as Ira Glass’s gap describes, and a friend dropping balls beside you makes it easier to keep going. Hall’s estimate of about 50 hours together to reach casual friendship is a reminder that shared hours add up.

Pick something small enough to learn in a week: three scarves, a card force, a phrase in a language neither of you speaks. Set a date to show each other.

DontSnooze can add a consequence to that date: if the alarm goes off and you do not record your 30-second proof, a random camera-roll photo goes to your friends, which makes a morning practice session harder to skip.

For a longer version of the same idea, Matt Cutts’s 30-day challenge picks one new thing and keeps it small enough to finish.

Twelve people did it for three months with three balls. A week with one friend and one trick is plenty to start with.