Based on A. R. Luria's (1966)[REF] seminal work on the modularization of brain function, and supported by decades of neuroimaging research, the PASS Theory of Intelligence[REF] proposes that cognition is organized in three systems and four processes.
One of Piaget's most famous studies focused purely on the discriminative abilities of children between the ages of two and a half years old, and four and a half years old.