2.1 - Biological theories of criminality Flashcards
Types of biological theories
Physiological, Genetic, Brain injuries/disorders, Biochemical
Physiological theories
Physical traits of the individuals (Lombroso, Sheldon)
Genetic theories
Inherited from family (Twin studies, adoption studies, Jacob’s XYY)
Lombroso’s Atavism theory
There are physical differences & traits that are different between criminals & non-criminals (examined skulls & facial features of criminals)
Atavistic
Not as evolved/earlier primitive stage of evolution where they are unable to control impulses & have reduced sensitivity
Physical characteristics of criminals according to Lombroso
- Enormous jaw
- High cheekbones
- Prominent eyebrow arches
- Handle-shaped ears
- Flat nose (thieves)/Pointed nose (murderers)
- Exceptionally long arms
Strengths of Lombroso’s theory
- Credible (Butcher & Taylor - less attractive individuals are more likely to be considered criminals - supports physical features leading to criminality)
- Scientific (first person to study crime using objective measurements to gather evidence)
Limitations of Lombroso’s theory
- Reductionist (not everyone with atavistic features is a criminal & vice versa)
- Ungeneralisable (lack of a control group in research - would’ve found non-criminals with same characteristics)
Sheldon’s somatotypes theory
Criminality is based off of body types (somatotypes) - advanced from Lombroso’s theory (examined 4000 men - college students or criminals - and categorised them into 3 types -> more likely to be mesomorphic if criminal)
3 types of somatotypes
- Ectomorph (thin & fragile, lacking muscle & fat, flat chest w/narrow hips & shoulders)
- Endomorph (rounded, soft, fat w/o muscle w/wider hips)
- MESOMORPH (more muscles, attracted to risk of crime)
Strengths of Sheldon’s theory
- Generalisable (larger sample size of 200 & control group of non-criminals to compare to)
- Credible (Glueck & Glueck - sample of delinquents had 60% mesomorphs where sample of non-delinquents had 31%)
Limitations of Sheldon’s theory
- Reductionist (Glueck & Glueck found criminality is best explained through a combination of biological, psychological & environmental factors - Sheldon claims only biological)
- Invalid (does not take into account how people’s somatotypes change & are not fixed at birth)
Twin studies
Study into monozygotic (identical) & dizygotic (fraternal) twins & if one MZ twin possesses a criminal gene, so will the other, but if one DZ twin possesses a criminal genes, only a 50% of the other possessing it (concordance rates)
Strengths of twin studies
- Credible (Christiansen found 35% concordance rate between MZ twins in 3586 twin pairs and only a 13% with DZ)
- Logical (studying MZ twins, that are genetically identical, is logical to examine whether the other is also offending)
Limitations of twin studies
- Ungeneralisable (small sample sizes in twin studies -> unrepresentative of general population)
- Invalid (impossible to isolate & measure effect of genes from environmental effects -> correlational data not causational)
Adoption studies
Comparison of child to adoptive parents (shared environment) & birth parents (shared genes) and any similarities to birth parents indicates crime is genetic
Strengths of adoption studies
- Validity (easier to separate genetic & environmental factors due to different environment in adoptive family)
- Credible (Mednick et al - 14000 adoptive sons, 20% criminal record similar to birth parents compared to 14% for adoptive)
Limitations of adoption studies
- Invalid (adopted children are placed in similar environments to birth family - leads to similar behaviour/age of adoption means they may already be influenced by birth parents or foster environment)
Jacob’s XYY theory
Some males possess an extra Y chromosome which leads to more violent/aggressive behaviour -> more criminal
Strength of Jacob’s theory
Credible
- Jacob et al - significant number of men in prisons had XYY rather than XY
- Alder et al - possible that aggressive/violent behaviour is at least partly determined by genetic factors
- Price and Whatmore - found links between XYY & property crime
Limitations of Jacob’s theory
Invalid
- XYY are tall & well built - fit stereotypes of violent offenders -> more likely to be sentenced -> overrepresentation in samples drawn from prisons
- Low intelligence -> more likely to be caught -> overrepresented
- Rare syndrome - cannot explain crime
Brain injuries & disorders
Crime is caused by significant injury to the brain or diseases that affect the brain
Key case (brain injuries)
Phineas Gage
- Intelligent, energetic & persistent
- Had a pipe go through his frontal lobe whilst working on a railway
- After recovery, his personality was more aggressive & distant
Disease
Linked with anti-social/criminal behaviour (Huntington’s, brain tumours)
Murderers had 11% reduction in activity in pre-frontal cortex (regulates emotions)
Example: Charles Whitman
- Murdered several people
- Discovered post-mortem that he had a brain tumour on the amygdala (regulates aggression & impulses) - also associated with fearlessness
Strengths of brain injuries/disorders
Scientific (correlations between abnormal EEG readings & psychopathic criminality)
Limitations of brain injuries/disorders
Unreliable (rare -> original personality more important in whether they engage in crime)
Invalid (unclear that abnormal brainwave activity causes criminality -> some psychopaths have normal EEG patterns)
Biochemical
Crime is caused by less/more of certain hormones
Serotonin
Linked to mood & impulsiveness (regulates blood sugar) - lower levels of serotonin linked with agression (Moir and Jessel)
Dopamine
Pleasure & rewarding feeling & desire to repeat behaviours - high levels of dopamine increases aggressive behaviour (Buitelaar)
Testosterone
Male sex hormone - higher levels associated with violence & aggression (M&F)
