and the water level were varied systematically on two levels. The glasses had an inner diameter of 25
or 65 mm and were filled with water up to 15 or 45 mm below the rim. Two glasses were used for the
practice trials; they were filled up to 30 mm below the rim. Fig. 2 shows schematically the drinking
glasses used in the practice and experimental trials. It also shows the angles at which the water would
reach the rim if the glasses were actually tilted. The normative tilting angles decrease with increasing
water level, and the tilting angles are larger for the thin glasses.