Numerosity – Genetic? Environmental? Predetermined and fixed? Changeable? There's room for optimism.

     

As I mentioned in an earlier post (about Dyscalculia screener), numerosity is the ability to represent, estimate and manipulate quantities.

This new article sheds more light on numerosity:

Why do we differ in number sense? Evidence from a genetically sensitive investigation.

  M.G. Tostoa, S.A. Petrill , J. Halberda , M. Trzaskowski , T.N. Tikhomirova , O.Y. Bogdanova ,R. Ly , J.B. Wilmer , D.Q. Naiman, L. Germine , R. Plomin, Y. Kovas. 

 Intelligence 43 (2014) 35–46

http://ac.els-cdn.com/S016028961300192X/1-s2.0-S016028961300192X-main.pdf?_tid=597f97e2-0d73-11e4-8029-00000aacb35e&acdnat=1405575160_5e8e1932bcc2f055dfab4594f8449661

Apparently, numerosity is a developing ability.  Six months old babies can distinguish between arrays of items of 4 from 8, and 8 from 16 (ratio 1:2).  Nine months old babies can discriminate between displays of 8 and 12 items (ratio 2:3).  Three year olds can distinguish between ratios of 3:4 and six year olds – of 5:6.  Adults can discriminate between arrays with ratios of 9:10 (!).  The ability to discriminate between quantities improves till the age of 30 and then begins to deteriorate.

The article describes a large scale research about numerosity with 16 year old twins.  The twins were presented with arrays of yellow and blue dots for a very brief time.  They had to decide whether there were more yellow or blue dots.  It was found, that numerosity correlates 0.3 with math achievement, 0.25 with processing speed, 0.22 with visual spatial working memory, 0.27 with nonverbal ability and 0.2 with language.

It was also found, that individual differences in numerosity among the 16 year olds were only modestly (32%) influenced by genetic factors.  Most of the variance was explained by environmental effects. 

Individual differences in the ability to distinguish between quantities appear as early as in 6 months old babies.  The authors suggest  that  in infancy, individual differences in numerosity are heavily influenced by genes, but in later development, numerosity is more affected by exposure to math stimuli, interest in activities with numbers and the amount of practice in math activities.  That means that numerosity can be trained and improved.  Even in infancy, 6 months old babies that received quantitative stimuli that were both visual and auditory, were able to distinguish between quantities with a ratio usually found in 9 months old babies.  It's possible that the multisensory information the babies received improved numerosity. 

It's also possible, that children born with poor numerosity and/or low general cognitive ability are less inclined to engage in activities with numbers and thus don't give their numerosity a chance to develop  to its full potential. 

That’s why it's especially important for children with poor numerosity not to give up and be exposed to math experiences and games.  This will help them train and improve their numerosity.