We present a review of empirical evidence that suggests that a substantial portion of phenotypic variance is due to nonlinear (epigenetic) processes during ontogenesis. The role of such processes as a source of phenotypic variance in human behaviour genetic studies is not fully appreciated. In addition to our review, we present simulation studies…

Although fear conditioning is an important psychological construct implicated in behavioral and emotional problems, little is known about how it develops in early childhood. Using a differential, partial reinforcement conditioning paradigm, this longitudinal study assessed skin conductance conditioned responses in 200 children at ages 3, 4, 5, 6,…

The study investigated children's intention understanding using a longitudinal design. Thirty-two Italian children were tested on the "Demonstration of Intention" in the Re-enactment paradigm devised by Meltzoff (1995a), at two ages. Mean age was 12 months at the first session and 15 months at the second session. Previous research by…