Social skills are dynamic developmental constructs typically measured using assessments developed via cross-sectional methods. The measurement model of derivatives (MMOD), a factor analytic approach targeting individual growth trajectories, was used to evaluate the longitudinal factor structure of the Social Skills Improvement System--Rating…

The balance between the preservation of early cognitive functions and serious transformations on these functions shifts across time. Piaget's writings, which favored transformations, are being replaced by writings that emphasize continuities between select cognitive functions of infants and older children. The claim that young infants possess…