ELECTIVE: FORENSIC PSYCHOLOGY
BIOLOGICAL BASIS OF CRIMINAL BEHAVIOUR
Þ developmental criminology
o adolescent-limited trajectory – the majority of youths engage in delinquent activities
at some point during adolescence but desist in early adulthood
o life-course persistent – offenders (mostly males) who start behaving antisocially early
and continue through adulthood
• minority (5-10%) but commit most of the crimes
Heredity & Crime
Þ heredity – transmission of genetic information from one generation to the next
o link between XYY and violent behaviour
• largely irrelevant
• small incidence of XYY
Þ intergenerational criminality
o high correlation between fathers’ criminality and the sons’ criminality
• equally applies to boys and girls
o however à other factors are also important
• social difficulties
• assertive mating – individuals mate with similar individuals
Þ twin studies – compare monozygotic (MZ, identical) twins and dizygotic (DZ, fraternal)
twins
if heredity has an influence, then the behaviours of MZ twins should show more
similarity/”concordance” than that found in the behaviours of DZ twins
o Lange 1929
• similarity rate for MZ twins with respect to criminality: 77%
• similarity rate for DZ twins with respect to criminality: 12%
• methodological problems (-)
o Christiansen 1977
• MZ twins: 35% concordance
• DZ twins: 12% concordance
o in summary: moderate relationship between heredity and antisocial behaviour
o equal environment assumption: the greater concordance found among MZ twins
compared to DZ twins is due to the influence of genetics since the environments of
twins are more or less the same
o new twin approach:
• the discordant MZ-twin method: assumption that MZ twins raised together do not
share exactly the same environments
§ microworlds
• strong correlation between hostile, cold mothers, and aggressive behaviour in
children
• Caspi et al., 2004
§ mothers did not treat each twin similarly
§ negative emotions expressed by the mother predicted aggression in their
child
§ concluded: it was the mother’s treatment and not heredity that explained the
child’s aggressiveness
Þ adoption studies
, o cross-fostering design – analyse the behaviour of
children who are separated soon after birth from
their biological parents and raised/fostered by non-
relatives
o analysed in relation to
• criminal history of the biological parents
• criminal history of adoptive parents
• particular combinations of criminality in the biological and adoptive parents
o small genetic effect
• adoptees raised by noncriminal parents but who had criminal biological parents
were at a higher risk of being convicted than adoptees from noncriminal biological
parents and raised by noncriminal foster parents
o follow-up investigation
• as the number of convictions for the biological parents increased à so did the
number for the adoptees
§ hold only for property offenses, not violent offenses
• parental criminality alone à insufficient in explaining violent crime in offspring
o epigenetics – how environmental stimuli can trigger/stop gene expression
• higher heritability was associated with the severity of the problem
Þ nature-nurture interaction
o eating meals with parents mitigated the effects of DRD2 gene (dopamine receptor
gene) on delinquency
o school attachments & repeating a grade à interacted with the MAOA gene (influences
aggression)
o the influence of heredity depends on the presence of certain environmental risk factors
• family dysfunction and low SES à increase heritability of antisocial behaviour
Neuropsychological Factors
Þ neurophysiological factors & crime
o amygdala (within the temporal lobe) forms the limbic system
• control basic emotions and motivations
• not totally responsible for aggressivity
o plasticity of the human brain – neighbouring neurons take over the functions of
damaged neurons
o violent behaviour: depend on a combination of processes within the limbic system
and the PFC
• criminal behaviour displayed a fairly large relationship with measures of executive
functioning
o PFC – attention, planning, inhibition of behaviour à speaking, executive functioning
• The frontal lobe develops throughout adolescence and the myelin continues to
develop into adulthood
• not fully developed until min. 25 y.o.
• might explain the age-crime curve
o delays in neurophysiological development affect attention skills, verbal language
development, and intelligence in general
o for life-course persistent offenders
• it may be actual impairment to the frontal lobe and limbic system
• poor performance on tests measuring verbal abilities à associated with life-
course-persistent male delinquents
o factors that lead youths into chronic criminality
, • biosocial model of life-course-persistent offending: neuropsychological factors,
temperament and socialisation experiences are incorporated
o biology-crime relationship à not direct, not simple
• environment plays a big role
Þ the difficult, impulsive, sensation-seeking temperament
o temperament – inherent, stable characteristic tendencies of responding to the
environment
• the biological precursor to personality
• explains the heritability of personality
• traits – big-picture descriptors of temperament
• facets – more specific descriptors that make up a trait
o difficult child:
• intense reactions to stimuli
• generally negative mood
• slowness to adapt to change
• irregularity in sleep, hunger, and other bodily functions
o significant stability of a difficult child
o temperamental traits important to an understanding of delinquency
• high stimulation-seeking combined with low self-control
• negative emotionality – aggression, alienation, stress reaction
§ life-course persistent scored higher
• callous-unemotional quality
§ exhibited by life-course persistent offenders
§ biologically based
o difficult temperament à predicted delinquency and aggressiveness as reported by
parents
• difficult (“lack of control”) temperament as predictive of maladaptive behaviours
at age 32
o a positive outcome for the child could result if the child has the “right” parents and
teachers, i.e., a match
• => major environmental risk factors are inappropriate parenting and poor parent-
child relationships
o what causes this energetic, impulsive, sensation-seeking temperament?
• neurophysiological arousal
• criminals à neurophysiologically underaroused
§ seek out stimulation and excitement
§ affects learning self-control
¨ antisocial behaviour may be traced to a breakdown in the biological
ability to effectively learn self-control
o critical inhibitory learning requires:
• antisocial behavior is punished
• the child has the capacity to learn to inhibit antisocial behavior
o learning of inhibition (self-control) to avoid punishment involves “fear reduction” à
passive avoidance learning
(1) child: contemplates an aggressive act
(2) previous punishment produces fear in the child (increased heart rate, blood
pressure, sweating)
, (3) fear (an unpleasant emotion) à causes the child to inhibit the aggressive
response in order to escape from feelings of fear
(4) the child no longer entertains the aggressive impulse, and the fear dissipates
(5) the immediate reduction of fear reinforces the inhibition of the antisocial act
• the process requires the ability to acquire the fear response and a rapid dissipation
of fear in order to receive the natural reinforcement for inhibition
• individuals with antisocial personalities à diminished fear responses to aversive
stimuli
§ once fear is aroused, the biological markers are slow to dissipate
o a deficit in passive avoidance learning may be due to other reasons, not fear deficit
• some may engage in criminal acts because the act feels good
• criminals tend to score higher on sensation-seeking
§ “high”, “rush” when committing crimes
è the neurophysiological arousal hypothesis provides a plausible explanation for criminal
behaviour in the absence of interpersonal/personally mediated controls
o possible link between poor nutrition, brain development and aggressive behaviour
Þ crime as a failure in evolution
o Lombroso
• unusual physical features – eye defects and oddly shaped noses
• criminal has similarities more common with lower-order animals than human race
à individuals I likely to behave like an animal
• atavism – the criminal is a biological throwback to an earlier evolutionary stage
• some criminals are simply born bad
• small samples (-)
Þ criminal behaviour as an evolutionary adaptation
o modern evolutionary theorists stress the successful adaption to the environment
• some forms of criminal behaviour can be understood as a product of successful
evolution
• risk-taking, aggression, dishonesty -> consensual sex w/o birth control, rape,
multiple sex partners à increasing the likelihood of offspring
o cads & dads
• cads – reproduce with women in sneaky, aggressive, cheating ways
• dads – remain monogamous
o 2 types of life-course-persistent offenders
• child with neuropsychological problems, difficult temperament, and poor
socialisation experiences
• psychopaths – follow an evolutionary adaptive, “life history” strategy
o delinquents and criminals
• begin sexual intercourse earlier than non-criminals
• have children earlier
• have more sexual partners
• tend to mate with partners who have similar temperaments, personalities, social
backgrounds
Closing comments
1. biological processes behind low self-control and negative emotionality increase the
probability of antisocial behavior under the right environmental conditions
2. assessment and treatment interventions need to include biological considerations
• biological factors can change as a result of treatment interventions
3. biological factors appear to play a greater role with the life-course-persistent offender
