Biological Level Of Analysis
How does or physiology and genetics
effect our behavior?
Development of Biological Perspective
• 370 BC….Hippocrates and his 4 Humors
Two things really catapulted us to
think that biology effected behavior…
1848
Phineas Gage
1859
Charles Darwin wrote “On the Origin of
Species”
• Idea that all species
developed over time with
the idea that “behavior is
adaptive”.
Outline the principles that define the biological level of
analysis and how they are demonstrated in research.
Studies
• Phineas Gage
• Bouchard et al
• Rosenzweig and Bennet
Terms
• Neurotransmitters
• Hormones
• Brain
• Evolutionary Psychology
• Monozygotic Twins
• Dizygotic Twins
• Concordance rate
• Cerebral Cortex
• Neuroplasticity
Principles of BLA
Outline the principles that define the
biological level of analysis
and how they are demonstrated in research
1. emotions and behavior are products of
anatomy and physiology and endocrine
systems
2. patterns of behavior can be inherited
3. animal research can help us understand
behavior
1. Emotions and behavior are products
of anatomy and physiology and
endocrine systems
Links have been found
between psychological
events and physiological
activities in 3 main
areas
• The effect of
neurotransmitters
• The effect of hormones
• The effect of brain
localization
Research Example
Phineas Gage
2. Patterns of behavior can be
inherited
Based on work of Darwin
• Genetics
• Evolutionary Psychology
Traits are passed on from generation to generation.
Especially those that help ensure our survival.
Research Example
Twins
Let’s take a better look at Twins….
• Monozygotic Twins (MZ
or identical) come from
the same sperm and egg
and share 100% of there
genes.
• Dizygotic Twins (DZ or
fraternal) come from two
different eggs and share
about 50% of their genes.
• Regular siblings also share
around 50% of their
genes.
Twins
In twin studies, researches
focus on something
called a concordance
rate…
• The probability that if
one individual has the
trait the other will also
have it.
• It tells us if a trait is
inherited.
Schizophrenia
Fraternal Twins: 15%
Identical Twins: 50%
• Usually in twin studies, one
twin acts as a control for the
other twin.
• In good twin research sets
of MZ are compared to sets
of DZ for a trait of disorder.
• High concordance rates
with MZ and lower with DZ
indicates the trait is due to
genes (inherited).
• Differences within pairs of
MZ are thought to be
environmental factors.
Bouchard et al. (1990)
Twin study investigating genetic inheritance in intelligence
• This study used a selfselected sample of MZ
twins who had been
reared together (MZT)
and MZ twins who had
been reared apart
(MZA).
• Looked at a lot of
factors but we will focus
on intelligence.
Bouchard et al. (1990)
Twin study investigating genetic inheritance in intelligence
Results:
• Used the WAIS to
measure intelligence.
• The concordance rates
for MZA was 69%, for
MZT it was 88%.
Bouchard et al. (1990)
Twin study investigating genetic inheritance in intelligence
• The researchers
concluded that
environmental factors do
play a role in
development of
intelligence but IQ is to a
large extent inherited.
• 70% of the observed
variation in the sample
could be attributed to
genetic variation.
Bouchard et al. (1990)
Twin study investigating genetic inheritance in intelligence
• They claim that in their
sample (white, middle
class, industrialized
nation) genetic
inheritance in IQ accounts
for around 2/3 of
observed variance of IQ.
• They also said that their
findings do not indicate
that IQ cannot be
increased by
environmental factors.
Bouchard et al. (1990)
Twin study investigating genetic inheritance in intelligence
Evaluation
• Correlational data cannot
establish cause/effect
relationships.
• Concordance rates were
high, but far from 100%.
• No control for the effect
of environmental
variables.
• Self-selected sample.
3. Animal research may inform our
understanding of behavior
• Based on Darwin’s idea
of evolution we share a
common ancestry with
animals.
• So in some ways we are
fundamentally the
same.
• Examples…..
Critical Periods
Imprinting
• the optimal period
• Conrad Lorenz
shortly after birth when • The process by which
an organism’s exposure
certain animals form
to certain stimuli or
attachments during a
experiences produce
critical period very early
proper development.
in life.
Harry Harlow and his Monkeys
• Discovered that
monkeys preferred the
soft body contact of a
cloth mother, over the
nourishment of a
hard/wirily mother.
Neuroplasticity
Although localization of
function does occur…
• The specific location of
that function is not
fixed for all individuals.
• It can change according
to environmental
demands
Rosenzweig and Bennett (1972)
Rosenzweig and Bennett (1972)
Findings
• Rats in the stimulating
environment had an
increased thickness in the
cortex.
• The frontal lobe (thinking,
planning , decision making)
was heavier in the rats that
had been in the stimulating
environment.
• Having toys created the best
conditions for developing
cerebral thickness.
Rosenzweig and Bennett (1972)
Issues
• These findings can be
generalized to human
only to some extent.
• it is difficult to decide
what is considered to be
an
enriched environmental
for a specific person.
• Rats were sacrificed
(Ethical)?