Neural correlates of postformal stages of reasoning: Biological determinants of developmental stage.

The latest research on developmental stage, according to the Model of Hierarchical Complexity (MHC), shows that there is only 1 domain, that stage develops as log2(age) and that the number of neurons of a species can predict the mean stage attained by that species. This can be interpreted as saying that biology controls stage. However, humans attain different stages and the biological mechanism that limits stage is still unknown. Based on these findings, we argue that cognitive neuroscience studies of human intelligence should shift from the general laws that govern development and brain maturation to focusing on interindividual differences across development, so as to complete the picture of human cognition beyond statistical norms. We here propose a study that looks for differences in patterns of the brain activation between subjects performing below and above formal stages. What differentiates this study from others that have been conducted in the field of developmental psychology and cognitive neuroscience is that this will explain for the first time not how, but why, some individuals are hardwired to perform at higher stages than others. We intend to analyze the data across different hierarchical complexity tasks and extract a saturation index (SI) that informs about the processing load of problem solving. Second, we compare the SI across subjects who attained different stages. This knowledge will provide for understanding the biological basis of cognition, for improving the behavioral predictive MHC, and for developing a connectionist model of cognition that emulates development throughout life.