Most of the processes that underlie thinking occur in the brain, which forms part of the central nervous system, which in turn transmits sensations and sends signals to muscles through the spinal cord and nerves.

Biological studies have shown that different regions of the brain are specifically involved in different cognitive functions such as: attention, memory, vision, hearing, and movement initiation as well as coordination and speech. Many functions are also dispersed throughout the brain.

With age there is a general slowing of intentional action and reduction in capability for attention. The ability to recognize patterns is also reduced. There is an increased susceptibility to distraction whilst attending to a task, resulting in reduced capability for tasks that require two or more simultaneous functions.

Well-established memories and skills are unaffected with age, whereas the time required to learn new things, make decisions and respond to sensory information increases, as can the frequency of errors.

Degenerative brain disorders are more prevalent with age, examples of which include Parkinson’s and Alzheimer’s diseases. These affect memory, attention, movement, perception, reasoning and social interaction to varying degrees.