Physiological psychology is a branch of psychology that looks at how the body and its systems affect our behaviors and thoughts. It's based on the idea that our physical bodies, such as our nervous system, hormones, and brain, can have an influence on our mental processes. For example, studies have found that people with higher levels of certain hormones, such as cortisol, tend to be more stressed or anxious. By understanding how the body and its systems work, we can gain insight into why people act the way they do.