Introduction to Biological Factors in Criminal Behavior

Overview

• Discussion on biological factors that may predispose individuals to criminal behavior.
• Key elements: genetics, brain structures, neurotransmitters, hormones.
• Relationship with the nature versus nurture debate.

Nature versus Nurture Debate

• Nature: Genetic predispositions.
• Nurture: Environmental influences on behavior.
• John Locke's concept of tabula rasa: Children can be shaped into various roles through environmental interactions.
• Emphasis on examining both sides and the potential interplay between them.

Studying Genetics and Environment

• DNA Analysis: Available since the 1990s but expensive.
• Identical twins (monozygotic) vs. fraternal twins (dizygotic) studies.
  • Identical twins share 100% of DNA, fraternal share about 50%.
  • Concordance rates used to measure similarities in behavior related to genetics.

Twin Studies

• Example of schizophrenia and ADHD heritability:
  • Schizophrenia: 50% chance if an identical twin has it.
  • ADHD: 75% chance for identical twins.
• Research findings on criminal behavior among twins:
  • Higher concordance rates in monozygotic twins suggest significant genetic influence.

Identical vs. Fraternal Twins

• Identical twins come from one fertilized egg, while fraternal comes from two.
• Shared environment vs. different genetics aids in studying behavioral outcomes.

Epigenetics

• Environmental factors can influence gene expression.
• Example: Thickened feet of homeless individuals from walking barefoot.
• Genes can be turned on or off based on environmental stimuli.

Summary of Findings on Criminal Behavior

• Research suggests genetics moderately contributes to criminal behavior, particularly in nonviolent crimes.
• Environmental factors are equally important.
• Conclusion: The nature vs. nurture debate is more about interaction than opposition.

Psychophysiology and Criminal Behavior

• Criminals may not respond to fear in typical ways; lower physiological arousal levels noted.
• Example: Travis Pastrana's fearless behavior may relate to psychophysiological traits.

Temperament and Personality

• Temperament affects how individuals behave from infancy through adulthood.
• Prenatal factors (toxins, alcohol) can influence future behavior.

Neurological Factors

• Importance of the frontal lobe and amygdala in regulating behavior:
  • Frontal lobe injuries can lead to impulsivity and behavioral changes.
• Famous case: Phineas Gage, who experienced personality shifts post-injury due to frontal lobe damage.

Hans Eysenck's Theory of Personality

• Introversion vs. Extroversion:
  • Introverts: High arousal levels; avoid stimulating activities.
  • Extroverts: Low arousal levels; seek out stimulating activities.
• Emotional Stability: Links to potential criminal behavior:
  • Extroverted individuals with low emotional stability may engage in more risky or aggressive behavior.

Conclusion

• Read the textbook for detailed studies and further understanding.
• Next topic: Psychopathy.