Emergent patterns in the development of young children's object play.

The present study set out to examine developments in object play in a contemporary sample of 289 typically developing children from 8- to 60-months of age. The value of object play centers on developments in object knowledge and mental representation, along with the developmental processes of decentration, substitution, and agency. The early play studies focused on one or another of these aspects of development, and generally for the age group 12-36 months.

Effects of Negation on Adolescents' Class and Conditional Reasoning Abilities.

Sixty adolescents (30 boys and 30 girls) evaluated conclusions for deductive arguments embodying four principles of class reasoning and their logically equivalent isomorphs in conditional reasoning. The presence or absence of the negative "not" was varied systematically in the major premise of the arguments. The results indicated that (a) there was a lack of improvement during early adolescence in the ability to reason with both class and conditional reasoning arguments, (b) the difficulty of specific principles of inference varied according to both the type of reasoning and the location of negation in the major premise, and