[learc83]

You can't really get any meaningful results from a self selected sample.

Since there is no other evidence that a 40 year old in the 90th percentile for mental performance is equal to a 20 year old in the 50th percentile, it seems more than likely that the data is skewed.

Perhaps Lumosity.com attracts above average young people and below average older people (given those results, some variation on that theme is the likely explanation).

[ktgrey]

For what it's worth, top chess players decline in skill with age, so it matters for at least one mental activity.

[learc83]

An otherwise almost imperceptible decline in mental function could have have a huge impact on ranking among top chess players simply because at the top levels the margins between players are so small.

If chess Grandmasters dropped in mental acuity as fast as those Luminosity results suggested, a 60 year old Grandmaster could be beaten by any young novice.

Also worth mentioning is that competitive chess is favors very quick thinking and action in a way that most careers don't.