If a graduate student studying the influence of biology on behavior and mental process what field of psychology with baby pursuing

If this graduate student wanted to see what influence biology has on a person's behavior and mental processes, the field of psychology that he would be pursuing is known as neuroscience.

Neuroscience has to do with the brain, and studying how brain's functions can affect the rest of a person's body, his thoughts, his behavior. It is a very important branch of psychology given that it is trying to explain the correlation between nerves and mental processes.