Evolutionary  psychology is the study of how natural selection selects for traits that promote the perpetuation of a persons genes, as well as, habits and tendencies.

Behavioral Genetics  is the study of how much our genes, and the environment, influence individuality and personal differences.  The most common traits studied are intelligence, personality, sexual orientation, and depression.  The effects of these traits on ourselves and the environment is a large issue.

Cognitive psychology is the study of how information is processed, stored, and retrieved.  Large focus is put on the brain and the different regions and their structures and functions. Sub topics include perception, attention, performance, memory, language, and thought.

Social - Cultural  psychology is the study of behavior and thinking and the tendencies for them to vary from one situation to another.  The effect of cultural differences and the weight and role they play in the thinking process is a major topic of research.  Traditional topics include social interaction, self regulation, mood, and social and cultural dynamics.

Behavioral Observation  is the study of how we learn observed responses.  Emotions are a major factor, largely fear, joy and sadness.

   There are many other branches of psychology.  Many minor topics are also investigated including drug effects, social counseling, prenatal development and infancy, psychology and law, personality, psychology of primates, and psych statistics.