Plenty is doing.
"....it is instructive to look at a principal components analysis of Piagetian items. A study by Garfinkle (1975) provides intercorrelations among fourteen Piagetian tasks administered to ninety-six kindergarten and first-grade children. The mean inter-item correlation is +.34.... The first principal component accounts for 40 per cent of the total variance in these fourteen items.... The communalities (which are close to the squared multiple correlation of each item with every other item) of the fourteen Piagetian items range from .41 to .80, with a mean of .61, which is comparable to what we find for Wechsler subtests.... But what makes this evidence even more striking testimony to Piaget's genius in devising test items* that get at the most fundamental aspects of intellectual development is the fact that the general factor of the Piagetian battery is almost pure g in the Spearman sense."
Disclaimer: this quote appears here only to spark discussion. It is not endorsed one way or the other. Make up your own mind. Or just refresh the page for another viewpoint. From a collection assembled by the late Chris Brand.