Principles

Everything psychological is simultaneously biological
Every psychological event occurs has a relationship the biologic.

The nervous system is complexity build from simplicity
The nervous system a build up with several complex system, it is link to other part of the neurons to from a complex system. The nervous system is simple in a way that it could only determine to fire or not fire.

The brain is both specialized and integrated.
Parts of the brain are specialized to work in certain ways. Both brains have to work together to function complex tasks.

The nervous system is plastic especially at early ages of development
Babies have more neurons to learn, it could be able to produce any kind of sound during the babbling stage. Adults have less neuron but they are linked together in complexity.