Chapter 6: Modern Biosocial Perspectives of Criminal Behavior

Biosocial Explanation

Genetics (nature) and environment (nurture) work together to influence human behavior, rejecting single-cause theories.

Four Main Biosocial Research Designs

Family studies, twin studies, adoption studies, and twins separated at birth.

Family Studies Finding on Parents

The criminality of the mother or female caretaker has a much stronger influence on children than the father's.

Major Flaw of Family Studies

They cannot separate nature from nurture because biological family members share both genes and household environment.

Twin Studies Methodology

Compares identical twins (monozygotic, 100% shared genes) to fraternal twins (dizygotic, ~50% shared genes).

Twin Studies Concordance Results

Identical (MZ) twins are far more similar in criminality than fraternal (DZ) twins.

Twin Studies Criticism

Identical twins look alike and tend to be treated much more similarly by their environment than fraternal twins, so environmental bias still plays a role.

Adoption Studies Methodology

Compares adopted children to both biological and adoptive parents to see whose criminal behavior they mirror.

Adoption Studies Nature Support

Adoptees with only criminal biological parents had a higher likelihood of criminality than those with only criminal adoptive parents which strongly supports the nature arguments.

Adoption Studies Major Flaw

Adoption agencies practice selective placement (placing babies into adoptive homes that closely resemble their biological families backgrounds).

The Mednick Study Criminality

a. no biological, no adoptive = 13.5%

b. no biological, yes adoptive = 14.7%

c. yes biological, no adoptive = 20%

d. yes biological, yes adoptive = 24.5%

Twins Separated at Birth Take-Away

Separated identical twins showed extremely similar criminal tendencies, strongly supporting the influence of heredity.

University of Minnesota Study

Found that separated twin pairs showed extremely similar tendencies for criminality, sometimes even higher than identical twins raised together.

Cytogenetic Studies

Focuses on an individual's genetic makeup, specifically looking for abnormalities in their chromosomes.

The XYY Factor

An extra Y chromosome found more often in mental patients, though modern research questions its predictive value.

Testosterone Link

An excessive amount of testosterone is consistently linked to aggressive and criminal behavior.

Dopamine and Crime

Both extremely high and extremely low levels of dopamine are linked to deviance and crime.

Serotonin and Impulse Control

Low levels of serotonin are consistently linked to criminal offending because it helps regulate impulse control.

The Warrior Gene (MAO-A)

A genetic mutation causing the MAO-A enzyme to malfunction, leading to severe behavioral and impulse-control problems. (breaking down dopamine and serotonin).

Autonomic Nervous System (ANS)

controls involuntary body functions (heart rate, pupil dilation, skin electrical conductivity).

Autonomic Nervous System (ANS) Finding

People with significantly low levels of ANS functioning are more statistically likely to commit crimes.

Stimulus Hunger

Low ANS arousal causes under-stimulation, leading individuals to seek out risky, thrilling experiences.

Biosocial Reality

Genetics and environment interact (ex. low birth weight babies were more likely to commit crimes, primarily if they were raised in a lower-income family prone with a weak social structure).

Behavioral Genetics Heritability

Meta-analyses show that genetic factors explain about 50% of the variance in antisocial behavior.

Diet and Incarcerated Juveniles

Placing incarcerated juveniles on diets low in simple carbohydrates reduced disciplinary violations by almost half.

Environmental Toxins (Lead)

A powerful neurotoxin that severely damages brain functioning, impulse control, and decision-making capabilities.