Individual-focused theories assume that certain biological or psychological factors may increase vulnerability to criminality. Research in this area highlights genetics, brain function, hormone levels, and other physical differences as possible parts of the explanation.

Researchers use several methods to investigate the relationship between biological factors and behavior.

Common research methods

  • Twin studies: compare identical and fraternal twins to estimate how much genes may influence behavior.
  • Adoption studies: compare adopted children with both biological and adoptive parents to separate heredity from environment.
  • Brain imaging: MRI and fMRI are used to study brain structure and activity.
  • Physiological measurements: pulse, hormones, and brain activity are measured to identify links to emotions and actions.
  • Neuropsychology: examines how brain functions influence thoughts, feelings, and behavior.

Risk factors, not destiny

The central point in this research is that biological findings describe risk factors, not destiny. A risk factor means that the probability of a certain behavior may increase under particular circumstances. It does not mean that a person is predetermined to commit crime.

Difficulties with impulse control, for example, may increase the risk of violent acts, but biological vulnerability always interacts with the environment. Upbringing, relationships, schooling, and living conditions influence how that vulnerability develops and is expressed.

What these theories explain best

Biological and psychological theories are especially useful for understanding antisocial behavior, aggression, impulsivity, and norm-breaking conduct. They are less sufficient when trying to explain every form of crime. Financial crime or ideologically motivated crime often require other explanatory models.

Individual-focused theories are most useful when they are combined with social and societal perspectives.

Sources: Granhag, P. A., Stromwall, L. A., Ask, K. & Landstrom, S. (2021). Handbook of Forensic Psychology. Liber. Howitt, D. (2002). Forensic & Criminal Psychology. Pearson Education.