Cognitive plasticity is the capacity to learn and improve cognitive skills such as solving problems and remembering events. Mercado argues that the structural basis of cognitive plasticity is the cortical module. Cortical modules are vertical columns of interconnected neuronal cells. Across different areas of the cerebral cortex, these columns vary in the number and diversity of neurons they contain. Identifying how cortical modules help us learn cognitive skills may help explain why variations in this capacity occur — that is, why people learn skills at different rates and why our ability to learn new skills changes as we age.