Early biological theories of criminology appeared in 19th-century Europe as a result of Cesare Lombroso’s writings on criminal types. Physiognomy and phrenology attempted to determine character by facial features and the shape of the skull. The body-type perspective, pioneered by Earnest Hooton and William Sheldon held that the shape of the body directly predicts criminality.
Early biocriminology was influenced by Gregor Mendel’s work in heredity and Darwin’s theory of evolution. Dugdale’s eugenics study led to the widespread belief that criminal forebears produced criminal descendants. The eugenics movement became popular during the first half of the 20th century, focusing on improving human breeding in the United States, partially by sterilizing social undesirables, including criminal offenders.
Modern biological research continues today. Most modern genetic researchers believe that both genes and environment are responsible for behavior rather than genes alone. Twin and adoption studies help researchers separate the influence of genes and environment. Some researchers hold that antisocial behavior influences human evolution, suggesting that socially inappropriate behaviors, such as rape and aggressive behavior, may have at one time played a useful role in human development. Other criminologists focus on the effects of neurological conditions on antisocial behavior, such as the effects of neurotransmitters, hormones, and brain structure. Some environmental elements are considered to affect antisocial behavior, including poor nutrition, exposure to harmful substances, and drugs and alcohol abuse. Biological theories are not popular in mainstream criminology but do have important implications for modern public policy.
Psychological theories, which focus on cognition and learned behavior, and psychiatric theories, which focus on neurological processes and illnesses, share a positivist approach with the biological perspective. Behaviorism proposes that behavior is determined by environment and learning, and suggests that operant conditioning may affect the frequency of antisocial behavior. Social learning theory holds that people learn behavior from watching others, then develop their own thoughts and attitudes about that behavior. Kohlberg’s stages of moral development attempts to explain how moral reasoning develops as children mature. Cognitive theorists also look at the relationship between IQ and language ability and crime.
Antisocial personality disorder (APD) describes a series of behaviors that produce severe and routine disregard for others. Psychopathy shares many symptoms with APD but is generally considered a distinct condition. Insanity is a legal term that describes an individual’s state of mind at the time he or she committed an offense.