NCBI ROFL: Left-handed people avoid using exact numbers.

By ncbi rofl | April 10, 2013 12:00 pm

If you’re ever engineering a nuclear power plant with a lefty, beware: apparently, the same features of their brain that make them left-handed might also make them avoid using exact numbers.  Even more surprising, just having a left-handed relative makes people more prone to rounding. Maybe this is why the Romans didn’t trust them, and “sinister” comes from the Latin word for “on the left side.”

Familial Sinistrals Avoid Exact Numbers

“We report data from an internet questionnaire of sixty number trivia. Participants were asked for the number of cups in their house, the number of cities they know and 58 other quantities. We compare the answers of familial sinistrals – individuals who are left-handed themselves or have a left-handed close blood-relative – with those of pure familial dextrals – right-handed individuals who reported only having right-handed close blood-relatives. We show that familial sinistrals use rounder numbers than pure familial dextrals in the survey responses. Round numbers in the decimal system are those that are multiples of powers of 10 or of half or a quarter of a power of 10. Roundness is a gradient concept, e.g. 100 is rounder than 50 or 200. We show that very round number like 100 and 1000 are used with 25% greater likelihood by familial sinistrals than by pure familial dextrals, while pure familial dextrals are more likely to use less round numbers such as 25, 60, and 200. We then use Sigurd’s (1988, Language in Society) index of the roundness of a number and report that familial sinistrals’ responses are significantly rounder on average than those of pure familial dextrals. To explain the difference, we propose that the cognitive effort of using exact numbers is greater for the familial sinistral group because their language and number systems tend to be more distributed over both hemispheres of the brain. Our data support the view that exact and approximate quantities are processed by two separate cognitive systems. Specifically, our behavioral data corroborates the view that the evolutionarily older, approximate number system is present in both hemispheres of the brain, while the exact number system tends to be localized in only one hemisphere.”

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  • Stan Curts

    I propose that this effect is from left-handed people being intelligent enough to realize that these survey questions weren’t worth the effort required to make an exact count of the number of cups in your house.

    • Sotres

      That’s exactly what I thought. As a lefty and engineer, I am very used to calculate with very precise numbers. But when someone comes and asks me how many cups I have in my house? WHO CARES?

  • Jonathan Peterson

    intersting. I’m a lefty – have always been particularly good at at doing rapid estimation math in my head. And have a strong aversion to fake exactness – I always round when telling the time from a digital source, because I KNOW that the source is likely off by at least 5 minutes. 5:20 seems so much more “human”

    • Octavio Beristain

      Yeap… thats me also.. another lefty.!!

    • nickshaw

      Ahhh, so this explains the obvious irritation when it’s noted that Skeeter is a lefty.

  • de Broglie

    Pres. Obama is left-handed. Maybe this explains his difficulty with quantitative thinking.

    • Jonathan Peterson

      thanks. just wouldn’t be the internet without someone douching up comments with partisan political stupidity.

      • nickshaw

        A world without people who make obvious connections?

      • Jonathan Peterson

        Article I, Section 9 of the Constitution, “No money shall be drawn from the treasury, but in consequence of appropriations made by law.”

        i.e. CONGRESS is responsible for the budget. how’s THAT for quantitative?

    • Oni

      This is a great observation. Maybe that’s why it’s taken 5 years to roll out a workable budget?

      • nickshaw

        Skeeter rolled out a workable budget?
        When did that happen?

    • epobirs

      Left-handedness is very high among Presidents relative to the general population.

  • Sotres

    I’m pretty sure a right-handed person wrote this article.

  • Casey Cheney

    Whoa, who invented the phrase “pure familial dextrals”? I’m going to start watching my impure familial dextral back. This stinks of mudblood-esque discrimination and condescension.

  • gekkobear

    So your analysis is from “the results from 200 participants in an online survey” …

    ** Remainder of post redacted for difficulty choosing how to mock this sufficiently **

  • 1ocu7u5

    surely this kind of ‘research’ should come with apostrophes and a disclaimer?

  • F. Sage

    Who says the Romans mistrusted the left hand because of how lefties used numbers?! This loose comment predisposed me to mistrust the whole report. The usual explanations are that 1. normally their own left hand was awkward and thus not to be trusted, but more important, 2. as most people are right-handed, an attack from the left hand would be a surprise. Thus the left was considered “sinister.”

  • Kevin Denny

    Dextrals and sinistrals don’t differ much in intelligence, on average. But I think you find more lefties at both extremes. There may be differences in cognitive style.

  • Jexiah8bit

    Left Handed Computer Scientist here who also hates counting cups.


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NCBI ROFL is the brainchild of two Molecular and Cell Biology graduate students at UC Berkeley and features real research articles from the PubMed database (which is housed by the National Center for Biotechnology information, aka NCBI) that they find amusing (ROFL is a commonly-used internet acronym for "rolling on the floor, laughing"). Follow us on twitter: @ncbirofl


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