Left Handers Club Newsletter – February 2014
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We recently asked Left Handers Club members to let us know their date of birth, male/female and country so we could do some analysis to see if left-handers differ from right-handers in their birth month.
Thank you to all who contributed. After removing duplicate entries and invalid data, we had over 3,100 entries which makes this by far the largest survey of its type ever analysed!
I think this can be considered a pretty random sample of birth date data for lefthanders (though it is skewed towards females because that is the balance of our customers and newsletter readers). I have done some initial analysis that DOES seem to show a difference in seasonality for left-handers. I have compared my left-handed results with overall birth rate statistics for UK, USA and Australia for 2010 (which do all seem to follow a pretty similar pattern) and charted the results.
The graph below shows the percentage of the annual total births that occur in each month. There do seem to be significantly higher births of lefthanders in July and August than expected from the normal overall trends. There is also a smaller but still significant-looking peak for lefthanders in January and February.
The patterns for male and female left-handers are very similar except for two marked differences:
We did try to analyse by decade but there seems to be a pretty wide variation in the data and as the sets for each decade are much smaller I am not sure how valid it is. The same goes for analysis by region and North / South Hemisphere.
To get some expert input into the analysis I sent the information and my analysis to Chris McManus, Professor of Psychology and Medical Education, University College London and author of the excellent book Right Hand, Left Hand. He broadly supported the analysis and was impressed with the number of responses we had received.
Our analysis of the data DOES seem to show some difference between the month of birth for lefthanders and the general population. However, as is often the case with research and analysis, it could well be that our data is skewed rather than this being a real underlying effect. But with such a large sample (compared to all the other samples that have ever been analysed) and with some clear differences that are NOT related to 13th August as well as the “Left Handers Day” effect, there may really be something to this.
That said, we cannot offer any theories as to WHY that might be the case so, although it was an interesting exercise, we do not really feel able to draw any strong conclusions from it.
Do you know better?
If this is you area of expertise and you have any comments, or you would like to do an independent analysis of the data, we would be very pleased to hear from you. You can add any thoughts as a comment below or you can find an anonymised version of the cleaned data here (it is in an Excel spreadsheet with a Pivot Table set up and also a linked sheet of country / region data and national birth rates data that you may find useful).
Thanks again to all who took part and we hope you found this interesting, if inconclusive!
You can see the full results and the feedback from Chris McManus in our article here and you can also add your thoughts as comments to that article.
We got a special deal from the manufacturer on this batch so we are offering them to Members only for the the month of February at a whopping 35% discount on the normal price. Don't miss out, we will not be able to do this again and we only have a limited stock at this price.
Normally £11.95 (USD 19.66), now just £7.77 (USD 12.78)
Enter Coupon Code LHC4K in the shopping cart and use the Update button to see your discount calculated
We recently had a message from Scott Conlan that encouraged us to do a bit of research. Sign language is used by deaf people as a system of communication using visual gestures and signs and your handedness clearly has an impact on how it is used and understood.
The British Sign Language (BSL) website has a section on left-handed signing and they say:
Left handed people who have just started to learn Sign Language often get a little bit confused about which hand they should be using as their dominant hand. The answer is that you should use which ever hand you feel most comfortable using, but you must remember to always use the same hand as your dominant handâ€¦ by swapping hands you can cause much confusion with those trying to read you.
We found this site about learning American Sign Language (ASL) which breaks down the different types of sign and how the dominant hand is used:
ASL is very different from BSL for historical reasons. There are records of a sign language for the deaf in Britain going back to 1570 and it has evolved from these origins by modification, invention and importation. ASL developed out of a system brought to the U.S. in the 19th century by a French teacher of the deaf. The signs used in the French system, mixed with signs that had been invented in America, combined to make ASL. There are some similarities (about 30% of the signs are the same), just like spoken languages have similarities, but they are not mutually intelligible.
We would be very interested in your experiences and comments regarding left-handed sign language so please add your views as comments to the online version of this article.
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