Twelve years ago, I wrote a post on this blog about the “10,000 hour rule” that Malcolm Gladwell promoted in his book Outliers. Gladwell claimed that 10,000 hours was the “magic number of greatness” – that 10,000 hours of practice was required to excel at an activity.  The author of the study that Gladwell cited as supporting this claim said that Gladwell misinterpreted the study’s results. Others have pointed out that the “10,000 hour rule” is misleading in suggesting that the total time spent on an activity is the only predictor of success. It doesn’t take into account other variables that might affect skill development, such as deliberate practice, innate or acquired talent, the age at which someone begins the activity, and access to appropriate equipment, coaching, and training sites.

While there are debates about exactly how much effect some of these variables have, it’s clear that Gladwell took the 10,000-hour figure out of context, and also skimmed over some important details that are necessary to fully understand how skill development works.

The post I wrote on the “10,000-hour rule” is by far the most popular post ever on this blog. That shows how interested people are in what Gladwell says. It also shows the importance of looking closely at his claims – to see what evidence he cites to support them, and to see whether experts on the subject agree with his interpretations.

This is not to say that only experts can discuss these kinds of topics. Sometimes an outsider can see details or trends that experts don’t notice. And there’s always a place for a writer who’s not a scientist or researcher to explain research and its outcomes to a general audience. But the writer needs to get the details right, and not simplify things to the point where important pieces of information are omitted.

Gladwell has just released a new book, Revenge of the Tipping Point. One of its chapters is about a new “magic number”: the “Magic Third”. This, Gladwell claims, is the number of minority members in a group that’s necessary for the minority to be accepted as part of the group. I’m going to look at this claim in detail because this general subject (organization and group dynamics) falls into my own area of professional expertise, so I have some familiarity with the relevant research.

The chapter subtitle of “The Magic Third” is a quote from one of Gladwell’s interviewees: “I would say, absolutely, there is some tipping point in my experience”. Notice that the quote doesn’t mention the “magic third”, or any number for that matter; it only says that there is a demographic tipping point which causes group dynamics to change. This type of change is well-documented in research on the effects of group composition. The fact that group dynamics change if group membership changes also won’t be a surprise to anyone.

Gladwell starts out by discussing (more…)