Michael Shayer says:
As to the sample and whether it was just in one neighbourhood, no, it was 10,000 large, and representative of England and Wales.
To me the other main finding is the push towards Concrete Generalisation, with those at the bottom going up, and those at the top way, way down. I remember years ago Jerry Bruner in the “Man, a Course of Study” created a game that was supposed to push them toward more abstract thinking. All the children did was to juggle around at random.
Yes, our results in the paper would have been better as a Figure would have been better, but there will be more to the story, probably with myself, James Flynn and Michael Woodley doing another paper. I found more information in Woodley’s last paper than he reported, and it agrees with my data.
At my request he send me three of his papers central to his research finding, which I list below.