Description: 3 beechwood boxes containing 3 sets of 7 small wooden shelves. One box contains a heavy wood (oak), the next a medium wood(10 grams lighter than the first), the last even lighter (10 grams lighter than the second).
Blindfolded, the child has to discern the differences in weight between the tablets, the error control being based on the color of the tablets, the darker colors being the heavier.
Direct aim: barium discrimination.
