Esbtimation of horizontality was tested by having three groups of 43 Ss in the first and third grades and first year college draw the water surface on pictures of tilted glasses, simulating a half-filled condition. The two primary grade groups did not appear to grasp the concept of horizontality, while college Ss made relatively accurate estimations. These results empirically supported the conclusion of Piaget and Inhelder (1956), reconfirmed Smedslund's (1963) results, and failed to confirm Rebelsky's (1964) conclusion that adults make as much error as young children.
RebelskyF.Adult perception of the horizontal. Percept. mot. Skills, 1964, 19, 371–374.
3.
SmedslundJ.The effect of observation on children's representation of the spatial orientation of a water surface. J. genet. Psychol., 1963, 102, 195–202.
