Humans (Homo sapiens) are the most abundant and widespread species of primates, characterized by bipedality and large, complex brains enabling the development of advanced tools, culture and language.

The five major perspectives in psychology are biological, psychodynamic, behavioral, cognitive and humanistic. Most psychologists would agree that no one approach is correct, although in the past, in the early days of psychology, the behaviorist would have said their perspective was the only truly scientific one.