Saturday 8 June 2013

By the age of three, a clear gap in ability

Jason  Malloy has been working on an interesting question, which is to determine at whether there is a clear gap in ability between black and white three year old children in America.

Some years ago there was much talk in Britain about tests which found that all racial groups began schooling at age 5 with identical “school readiness” results, but then progressively diverged as the years went by, strongly suggesting that schools were failing to teach British black children properly. I was never able to get to the bottom of what these tests were, and what range of skills they covered, and whether there were ceiling effects on the tests, but it was clear that pre-school intelligence testing results would cast light on whether children of different genetic backgrounds really started school with the same level of ability.

Malloy found 29 usable studies containing 35 different samples of children born between 1936 and 2000. There is IQ data for 2569 black children and 2762 white children, age 3

“A majority of these samples contain control groups of whites who were tested at similar times, and under similar conditions. When we compare the 20 samples with both blacks and whites, we get a difference of almost exactly 1 standard deviation: the black IQ is 85.4 and the white IQ is 100.8 (15.4 points/1.03σ).”
The figure shows the studies plotted out by year.

There is no particular trend (one early outlier study was excluded) and the pre-school intelligence gap looks pretty solid. The next post will discuss measurement issues. The predictive power of intelligence tests increase with subject age. Conventionally 7 years gives the first reliable indication of adult intelligence. 11 years is far better, but there is still more maturation to take place.

One more post to follow on this topic.  


  1. The way we were streamed in Primary School was priceless. They assigned us for our first term to the top or bottom stream arbitrarily, then after a term reassigned us on what they had seen of our abilities: so there we were, two classes of about 45 pupils each.

    And how was the arbitrary assignment done? If the old girl in charge had taught your parents you went in the "top" stream.

  2. Why, how shockingly racist you are, Dr. Thompson!!

    1. > race (which is a man-made not a biological concept)

      Seeing as IQ is mostly genetic, do you believe that skin colour, bone structure and height man-made concepts too? What about genetic diseases? Or does "sickle cell anaemia is a social construct" sound too obviously stupid?

      >Anything other than accepting that we are all human

      We're all human whether there race is biological or not.