For incoming students who may not be familiar with the field, a broad definition of modern psychology is "the science of behavior." How we learn, how we act, and how to measure both are the principal topics of study in psychology. Psychologists investigate topics such as personality, learning, memory, language, emotion, aggression, intelligence, group behavior, and the assessment and treatment of mental disorders. As a discipline, psychology might be thought of as between biology and philosophy in its methods and goals. Like biologists, psychologists have an interest in the brain and other functions that affect human behavior. On the other hand, like philosophers, psychologists are concerned with man as a social being whose interpersonal, moral, and religious behavior is greatly influenced by what other people say and do, including parents and teachers as well as people who lived thousands of years ago. They ask the age-old questions of what constitutes happiness and how one can remain true to oneself while adjusting to others.