Psychology is one of the behavioral sciences — a broad field that spans the social and natural sciences. Psychology attempts to understand the role human behavior plays in social dynamics while incorporating physiological and neurological processes into its conceptions of mental functioning. Psychology includes many sub-fields of study and application concerned with such areas as human development, sports, health, industry, law, and spirituality.

Psychology describes and attempts to explain consciousness, behavior, and social interaction. Empirical psychology is primarily devoted to describing human experience and behavior as it actually occurs. Since the 1980s, psychology has begun to examine the relationship between consciousness and the brain or nervous system. It is still not clear how these interact: does consciousness determine brain states or do brain states determine consciousness - or are both going on in various ways?

There are several branches of psychology. Comparative psychology refers to the study of the behavior and mental life of animals other than human beings. It is related to disciplines outside of psychology that study animal behavior, such as ethology. Although the field of psychology is primarily concerned with humans, the behavior and mental processes of animals is also an important part of psychological research, either as a subject in its own right (e.g., animal cognition and ethology), or with strong emphasis about evolutionary links, and somewhat more controversially, as a way of gaining an insight into human psychology by means of comparison or via animal models of emotional and behavior systems as seen in neuroscience of psychology.

Personality psychology studies enduring psychological patterns of behavior, thought and emotion, commonly called an individual's personality. Mainly focusing on the development of the human mind through the life span, developmental psychology seeks to understand how people come to perceive, understand, and act within the world and how these processes change as they age. This may focus on intellectual, cognitive, neural, social, or moral development.

Quantitative psychology involves the application of mathematical and statistical modeling in psychological research, and the development of statistical methods for analyzing and explaining behavioral data.

Psychometrics is the field of psychology concerned with the theory and technique of psychological measurement, which includes the measurement of knowledge, abilities, attitudes, and personality traits.