A methodological investigation of Piaget's theory of object concept development in the sensory-motor period

A sample of 84 infants, ages 6, 8, 10, 12, 14, 16, and 18 months, were tested under one of two conditions in Piagetian-type tasks derived from a series proposed byUzgiris and Hunt (1966). The Replication (R) Condition closely followed the administration outlined by Uzgiris and Hunt except that the testing conditions and number of trials for each task were standardized. The Extension (E) Condition contained a number of additional controls for possible confounding variables: task orders followed a Latin square design, objects were hidden under identical clothes, and the right-left order of trial presentation was counterbalanced. Each S received 8 of the 15 tasks studied presumed to span the limit of abilities evidenced by that age S. Infants' search behaviors were scored independently by two observers with 98% agreement. The pattern of results was consistently but generally not significantly more reliable in the E Condition than in the R Condition. Consistent age changes were evident, suggesting two overlapping developmental dimensions: the ability to deal with visible versus invisible displacements, and with nonsequential versus sequential displacements. The trend of the data suggested, contrary to previous evidence, that the infant can cope with single invisible displacements not involving movement before he can handle complex visible displacements that do involve movement. Evidence for ordinal development, examined by the Green test, a Guttman-type scaling measure, was minimal, and several tasks were not performed as expected from Piaget's theorizing and previous findings. The present method was concluded to be promising for use in future investigations.