Topic 3: Biological Factors Flashcards
What is behavioral genetics?
a quantitatively oriented science that attempts to estimate the relative contributions of both heritable and environmental factors to human behavior
Francis Galton was among the first to study the heritability of non-physical phenotypic features
some traits (e.g., eye color) are determined by single genes, the expression of one phenotype over the other results from dominance or incomplete dominance
characteristics of interest to psychologists are generally polygenic
What does polygenic mean?
influenced by multiple genes
for example, intellectual functioning can be influences by genes that regulate neurotransmitter function, cerebral morphology, blood flow, etc.
Does behavioral genetics imply determinism?
no
but we are born with predispositions and a variety of talents, weaknesses, etc.
other than in extreme cases, this does not imply absolute control by our genes
this is often true in physical medicine also; e.g., diabetes can be highly debilitating but exercise, healthy diet, and sometimes medication can dramatically offset those effects
What is heritability?
heritability, or h2, is formally defined as the ratio of genetic variance to phenotypic variance
more simply, what proportion of the observed trait’s expression can be chalked up to genetic factors
since it’s a proportion, it can range from 0 (no identified genetic contribution) to 1 (all variance is genetically based)
What is important to note about heritability estimates?
give us an idea of how important genes are to the expression of a given trait
are based on whole populations, they are not specific to individuals
may vary from one population to another
are heavily dependent on the measurement approaches used to assess a given trait
What is variance?
technically it’s a statistical term, s2
so really it quantifies the amount of “spread” in a given population WRT some variable such as intelligence, criminality, height, etc
when we use this term it’s often in the context of accounting for individual or group differences
can be great or small
this concept isn’t restricted to discussions of criminality; the expression of virtually any psychological variable or construct can be examined in this way: h2 is never 0 in psychology
What is genotype and phenotype?
genotype refers to the alleles possessed by an individual organism
phenotype refers to the manifested characteristics of that organism
What is polygenic determination?
several genes contribute to the expression of a certain characteristic
e.g., physical factors affecting intelligence include blood flow, neurotransmitters, cerebral morphology, and many more
each of these, in turn, may be polygenically influenced
Is heritability constant over time?
no, since the total variance (degree of variability) in any trait can change, so can h2
therefore, to say that genetic variance affects a characteristic does not limit environmental effects
this is about genetic differences between one organism to another; not about nature vs. nurture
What are shared environmental effects (c2)?
those aspects encountered by all members of a certain group
e.g., full siblings raised by their biological parents share exposure to the same set of parents, siblings reared apart do not
What are non-shared environmental effects (e2)?
encountered uniquely
e.g., your peer group, the fight you had in grade 4, your gender and age
What is epigenetics?
the study of changes in the expression of genes that do not result from alterations in the sequence of the genetic code (APA)
some genes are “switched on” or “switched off” in response to some environmental factors, which could include certain stressors such as trauma
DNA methylation, occurs when molecules called methyl groups attach to certain pieces of DNA, which can attach to certain pieces of DNA, which can affect a gene’s expression
What is the serotonin (5-HT) transporter gene (SLC6A4)?
lower levels of 5-HT are associated with increased aggression
hypermethylation essentially contributes to lower 5-HT synthesis
What is the oxytocin transporter gene (OXTR)?
related to empathy and emotional regulation
when genes are shut off there is decreased empathy
What is the monoaminoxidase (MAO-A) promoter?
initiates transcription, which is the first step in expression
hypermethylation is associated with increased aggression and ASPD
What is the dopamine receptor gene (DRD1)?
more methylated in aggressive boys and girls
may be related to relatively lower executive functioning and cognition
How do the differences in the quality of interaction between individuals moderate environmental effects on behavior?
obviously, there are differences in the quality of interaction between individuals and otherwise shared environments that moderate environmental effects on behavior
these are correctly placed in the non-shared category
e.g., mom is closer to your younger sister and spends more time with her; though you have the same mother, the influences she exerts on your behavior are likely to be different than those she exerts on your younger sister; this refers to your evocative style
What is evocative style?
behavior we have that bring out behaviors or feelings in others
the way we bring out certain behaviors in other people
How do twin studies contribute to our understanding of crime?
we can exploit the fact that certain sibling pairs vary in their degree of genetic similarity
MZ twins: genetically identical
DZ twins: share half their genetic constitution (on average)
non-twin siblings: also share half their genetic constitution (on average)
since some siblings are reared apart, and others together, we have a “pre-built” way to examine the effects of environmental diversity
What are twin studies?
Raine (1993) completed a meta-analysis of 13 twin studies
results: concordance
DZ: 20.6%
MZ: 51.5%
objection: gene effects were confounded with environmental effects
What is the heritability formula in twin studies?
h2 can be estimated by examining the difference in correlation between MZ and DZ twins
h2 = 2(rMZ - rDZ)
What are common heritability levels in twin studies?
h2 estimates fall into the (0.30 to 0.40) range
c2 estimates fall around 0.30 but decrease dramatically over the lifespan (to about 0.05) as e2 and h2 increase
why?: parental control/influence decreases, total variability increases
h2 is much higher for “component” traits like fearlessness, aggressiveness, IQ, impulsivity, sensation seeking
What are adoption studies?
intended to separate heritability from environmental effects
What are the two strategies for adoption studies?
strategy one: follow children adopted from criminal families, compare conviction rates with non-adopted controls
problem: while this addresses h2 it neglects e2
strategy two: follow children adopted from, and into, both criminal and non-criminal families, compare conviction rates
What are the objections to adoption studies?
adoptive homes are more alike than others (r = 0.30)
tend to affluent (higher SES)
carefully screened
this decreases variability to well below random levels
these effects would artificially suppress e2 estimates if a researcher was working under the assumption that r = 0
i.e., would lead to the conclusion that a higher proportion of observed variance stems from heritable contributors
What are the conclusions about the biological factors of criminality found in research studies?
genes play a significant role in the expression of criminal behavior
environment plays a significant role too
criminal behavior is best understood in terms of the interaction between genetic and environmental factors
What are conceptual nervous system (cNS) models?
theory about the functioning of the CNS based on, and able to accommodate existing data
can be based on both psychological and physical properties
may emphasize different aspects of functioning; in AS behavior, sensation seeking, aggression, failure to learn from certain types of experience
What is the Ascending Reticular Activating System (ARAS)?
based on ARAS levels
assumed high level of between-subject variance: receives input from most major sensory systems, involved in sleep-wake transitions and level of cortical arousal
assumed to influence more fundamental processes (learning, motivation, etc.)
differences in ARAS activity are genetically determined; results in differences along the orthogonal dimensions of introversion-extroversion, psychoticism, and neuroticism
What is the three-factor model?
Introversion-Extroversion: drive to interact with people
Psychoticism: person ability to adopt the perspectives of other people
Neuroticism: how reactive they are emotionally
I-E, P, and N influence pre-disposition (personality), and therefore one’s tendency to engage in criminal behavior: they are moderator variables, same physiological characteristics can lead to different behaviors
Eysenck have presented evidence that prisoners score higher on measures of N and P than controls, though the greatest hypothesized differences (I-E) were small
What is Gray’s Model?
based on septohippocampal system (SHS)
model deals with organism’s responses to conditioned stimuli
BAS: behavioral activation system (approach)
BIS: behavioral inhibition system (avoidance)
NAS: non-specific arousal system
BAS and BIS operate on basis of reciprocal inhibition, both can increase NAS
BAS is sensitive to (activated by cues) for reward and active avoidance
BIS is activated by cues for punishment and non-reward; also serves to re-focus attention toward other cues
NAS modulates the intensity of behaviors triggered by both systems
How does Gray’s Model explain criminal behavior?
criminals are seen as having an imbalance
BAS activity predominates
BIS fails to inhibit goal-oriented behavior in the presence of certain cues (including socialized values)
the model fits well with experimental findings such as: deficient passive avoidance learning, high aggressiveness, low anxiety (low EDR), impulsivity
What is brain injury?
at times, traumatic brain injury (TBI) or the onset of illness will mark the emergence of highly antisocial, aggressive behavior
sometimes in a previously peaceful, law-abiding individual
more frequently in someone that showed those tendencies at a lower level beforehand
Who is Phineas Gage?
tamping rod went through his brain
personality changes: heavy drinking, unreliable, almost unemployable
What are examples of personality changes after brain injury?
agitation
irritability
short-temper
failure to discontinue harmful, maladaptive behavior (perseveration)
obsessions
confusion/frustration
compromised insight/abstraction
What is the percentage of aggression attributable to TBI?
actual outbreaks of aggression attributable to TBI are not that common (about 11% of patients)
tends to be unfocused when it occurs
no real underlying reasoning or planning
most likely in acute phase of injury
not clearly related to severity of injury (95% are mild or moderate)
may be secondary consequences to frustration over poor memory, low mood, lost abilities
tolerance of exogenous substances often lowered
more typically threats are uttered, or language becomes vulgar and/or threatening
What deficits occur after a frontal lobe injury?
higher executive functioning and inhibition
most common site of injury
two patterns emerge:
lethargic, apathetic, indifferent (diffuse)
impulsive/aggressive (orbital-frontal)
some knowledge gleaned from lobotomy patients
What deficits occur after a limbic system injury?
deep mid-brain structures, e.g., amygdala and hippocampus
involved in emotional regulation as well as memory consolidation
humans with damage in those areas are often highly emotional; fear can switch to anger very quickly
a number of case studies record high levels of aggression in previously peaceful patients: often there is elaborate planning, so it can’t be entirely impulsive
What deficits occur after during temporal lobe epilepsy?
fast, spike-like activity (localized seizures) in EEG recordings over the temporal lobes is sometimes accompanied by increased risk for aggression
may be followed by confusion and limited recall
What are the effects of neurotransmitters and testosterone on aggression?
all are essential, and none are specifically connected to level of aggression
testosterone levels in males is positively correlated with aggression
NE and ATCH levels are sometimes elevated in bipolar disordered patients
