Take this with a grain of salt (using whichever hand you prefer).

An analysis of results from a scratch-and-sniff survey in National Geographic from 1986 (stay with me) showed Mainers had the highest rates of left-handedness in the country, among white people born after 1950.

Why are we talking about a scratch-and-sniff survey from the 1980s? Because as well as asking respondents what they smelled, it contained a questionnaire, which included two questions on which hand respondents preferred — one asked about writing, and the other asked the preferred throwing arm. The firm that made the survey was working on the hypothesis that hand preference and smell could be linked. (It turns out that it’s not.)

Fast forward to 2009. A University College of London researcher took that data — which includes responses from 1.4 million people — and mapped it by state.

The researcher, Chris McManus, pointed out that this survey ended up being an important source for research on what’s known as handedness.

Regardless of the sample size, these data are hardly scientific, as the Post notes:

As an opt-in survey of magazine readers, it has obvious weaknesses. Ninety-seven percent of respondents were white, and National Geographic readers in the 1980s were almost certainly economically and demographically distinct from the general population in other ways, too.

But 1.4 million people is still a lot of data points, the Post points out, and this survey still “created the largest dataset of hand preference ever constructed.”

Here’s McManus’ map, which showed that 13.7 of Mainers born after 1950 are lefties. (I’m not sure why Maine’s outline appears to include part of Canada. The description of the map assures us that it’s just for the United States.):

Here’s a much prettier version of the map, built by the Washington Post.

Featured homepage image by SparkFun Electronics on Flickr.