3 - Biological Factors

the conceptual nervous system (cNS) is a ____ model

bridging

behavioural genetics

quantitatively oriented science that attempts to estimate the relative contributions of both heritable and environmental factors to human behaviour

dominance

when the expression of one phenotype is shown over another

polygenic

influenced by multiple genes

• characteristics of interest to psychologists typically polygenic

predispositions

a liability or tendency to suffer from a particular condition, hold a particular attitude, or act in a particular way

• negative or positive

heritability

h²

ratio of genetic variance to phenotypic variance

• the proportion of observed trait’s expression can be chalked up to genetic factors

• range from 0 to 1

heritability estimates

• give idea to how important genes are to expression of given trait

• based on whole populations

• dependent on the measurement approach

variance

quantifies the amount of ‘spread’ in a given population such as intelligence

• wider bell has more variance

genotype

alleles possessed by an individual organism

phenotype

manifested characteristics of an organism

polygenic determination

several genes contribute to the expression of a certain characteristic

is h² constant over time?

no, since variance in any trait can change so can heritability

• about genetic differences, not about nature vs. nurture

two types of environment effects

shared environment (c²) and non-shared (e²)

shared environment

(c²) aspects encountered by all members of a certain group

• ex., siblings raised by same parents

non-shared environment

(e²) things encountered uniquely

• ex. your peer group

epigenetics

study of changes in the expression of genes that do not result from alterations in the sequence of the genetic code

• some genes switched on or off due to trauma or other stressors

• DNA methylation

DNA methylation

when molecules called methyl groups attach to certain pieces of DNA, can affect gene expression

(epigenetics)

serotonin transporter gene

SLC6A4

lower levels of serotonin associated with increased aggression

oxytocin transporter gene

OXTR

related to empathy and emotional regulation

monoamineoxidase promoter

MAO-A

initiates transcription, first step in expression

hypermethalyation associated with increased aggression and ASPD

dopamine receptor gene

DRDI

more methylated in aggressive boys and girls

related to lower executive functioning and cognition

evocative style

even though you and your sibling have same mother, the influence she exerts on your behaviour is different than your siblings

concordance

sameness

twin study results

monozygotic twins have higher concordance of criminality

• problem: gene effects are confounded with environment effects

confound

something else exists that makes it difficult to truly attribute results to the independent variable

h² can be estimated by examining the difference in______ between MZ and DZ twins

correlation

h² estimates fall into the ______ range

0.3 to 0.4

c² estimates fall around 0.3 but _______ dramatically over lifespan

decrease

• due to parental influence decreasing and total variability increasing

h² higher for ______ traits like aggressiveness, IQ, impulsivity

component

adoption studies (including the two methods)

help separate heritability from environmental effects

1. follow children adopted from criminal families

   1. problem: neglects e², could have influences from bio parents prior to adoption

2. follow children adopted from and into, both criminal and non-criminal families

results of Mednick’s adoption study

criminality in sons highest when biological and adoptive parents were criminal

• interaction effect

• biological influence greater than the environmental, as those with biological criminal parents had higher convictions than just adoptive criminal parents

objections to adoption studies

• adoptive homes more alike than others due to SES, screenings, etc.

  • effects artificially suppress e² estimates

criminal behaviour best understood in terms of an _____ between genetic and environmental factors

interaction

cNS model

conceptual nervous system

• theory about functioning of CNS

• based on psychological and physical properties

• emphasizes different aspects of functioning

• general model, not just for criminality

Eysenck’s three-factor model

• based on ARAS levels

• results in differences along orthogonal (uncorrelated) dimensions of I-E, P, and N

• I-E, P,N influence pre-disposition (personality), therefore one’s tendency to engage in criminal behaviour

• moderator variables

ascending reticular activating system

ARAS, plays role in the three-factor model

• receives input from major sensory systems

• involved in sleep-wake transitions and level of cortical arousal

cortical arousal

background activity / noise in the brain, everybody has a different preferred level

• role in ARAS

extraversion (TFM)

find absence of social interactions distressing, draw energy from social interactions

• low background activity / cortical arousal

• ex., sex offender

introversion (TFM)

do not seek stimulation, they find performing exhausting

• high background activity / cortical arousal

• ex., cyber criminal

high psychoticism (TFM)

• autism scale

• don’t see self as integrated into society, see others as fixtures or resources

• no empathetic reaction or perspective taking

• ex., psychopath

low psychoticism (TFM)

• overly enmeshed with others

• difficulty separating self

stable neuroticism (TFM)

opposite of neurotic

ex., pilot

unstable neuroticism (TFM)

• measure of how quickly emotional state can change in reactivity

• ex., second or third degree murder

problem with TFM

most criminals commit many different types of crime

prisoners score higher on which TF variables?

neuroticism and psychoticism, even though they thought I-E would be the biggest difference

gray’s model

deals with organism’s responses to conditioned stimuli

• based on septohippocampal system (SHS)

  • for learning and memory

• BAS, BIS, and NAS

behavioural activation system

(gray’s model)

sensitive to reward and active avoidance

• operates on basis of reciprocal inhibition with BIS

• established by learning

active avoidance

a behaviour is completed to avoid, doesn’t have to be conscious

passive avoidance

not acting leads to avoiding an undesirable outcome

behavioural inhibition system

(Gray’s model)

activated by cues for punishment and non-reward. serves to re-focus attention toward other cues

• operates on basis of reciprocal inhibition with BAS

non-specific arousal system

(Gray’s model)

modulates the intensity of behaviours triggered by both systems

how does the gray method explain criminal behaviour?

criminals have an imbalance

• BAS activity predominates

• BIS fails to inhibit goal-oriented behaviour (either something fundamentally different in brain or parental punishment was non-contingent)

traumatic brain injury

the onset of illness can mark emergence of highly antisocial, aggressive behaviour

• more frequently in someone who had those tendencies before

outbreaks of aggression attributable to TBI are ___ that common

not

• typically verbal threats rather than physical aggression

• not clearly related to severity of injury

coup contracoupe injury

coupe is the first impact at the back of the head, contracoupe is when the front takes the most damage

which lobe is the most common site of injury?

frontal lobe, due to car accidents

two patterns of frontal lobe injury

1. lethargic, apatehtic, indifferent (diffuse)

   1. lobotomy

2. impulsive / aggressive (orbito-frontal)

   1. hit by bat

limbic system

deep mid-brain structures (amygdala and hippocampus)

• involved in emotional regulation and memory consolidation

• damage here makes us highly emotional

80 / 20 rule

at the one year mark of recovery 80% will have taken place, 20% between year 1 & 2

temporal lobe epilepsy

fast, spike-like activity in EEG recordings over temporal lobe, accompanied by increase risk for aggression

• followed by confusion and limited recall

most physiological correlates of increased aggression likely have an _____ _____

indirect effect

_____ ______ remains an important predictor of aggression after TBI

pre-morbid persoanlity