Li et al (1999)
Piaget and Inhelder's (1956) study of conservation is a classic in developmental psychology. Part of their research required children to correctly predict the water surface orientation in bottles that were half-filled and then tilted. As you can see by the image on the left, the tilting of the bottle always results in a horizontal line. Piaget and Inhelder would argue that this was part of a child's cognitive...