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You could research genetically influenced personality traits such as shyness, aggression, depression, anxiety or sexual orientation.

Try Wikipedia..

http://en.wikipedia.org/wiki/Biological_psychology

You could just write a paper on the main parts of the brain and what each does to allow us to opperate everyday. here is a list of the most important parts

amygdala

cerebrum

corpus callosum

thalamus

hypothalamus

pituitary gland

hippocampus

pons

medulla

spinal cord

brainstem

cerebellum

Consider long term disease; like Diabetes. The prevalence of depression among Diabetics is huge. It like everything else in their lives is changed by the changes in their glucose (insulin) and hormonal levels. Physical triggers to psycological changes.

Combine this with the effect of this disease physically and you understand the progression of depression.

This is just one example.

Take any chronic , life threatening disease........ and extrapolate.

evaluate averting counseling. Neuropsychology is composed of detecting recommendations injury via a chain of exams. via the content textile of your question, i'd advise which you steer away from communicate treatment of any form.

How about animal behaviour? Like why do dogs sniff other dog's butts lol.