Research Methods in the Biological Level of Analysis
Rida Aamer & Haris Saud
Learning Outcome: Discuss how and why particular research methods are used at the BLOA.
Key Terms Defined
Experiment: A quantitative research method in which
a cause-and-effect relationship between two variables
is established.
 Independent variable is the variable that is
deliberately manipulated and causes a change
in the dependent variable. The independent
variable has two or more conditions, one of
which is the control condition.
 Example: An experiment manipulates the noise
in a room (no noise being the control condition)
to test the recall of words by participants. All
other variables are controlled for.
Case Study: Observations of behavior of a specific
individual or group of individual to provide highly detailed
and rich qualitative data.

Example: A case study of a person with a very
rare genetic disorder, such as hypertrichosis.
Correlational study: A quantitative research method
using co-variation – when one variable changes, the
other variable changes as well; however, no cause-andeffect relationship can be determined
 Positive correlation  both variables change
in the same direction (e.g. as x increases, y
increases).
 Negative correlation  two variables change
in different ways (e.g. as x increases, y
decreases).
 Example: A correlational study could investigate
the average number of hours a child watches
television and the child’s level of aggression
First Sentence of SAQ: Three research methods used at the biological level of analysis are the experimental method,
the correlational study, and the case study; these are demonstrated in studies done by Rosenzweig et al. (1972),
Bouchard et al. (1990), and Harlow (1848), respectively.
Thesis of LAQ: This paper will investigate how and why the experimental method, the correlational study, and the
case study are used at the biological level of analysis with reference to studies done by Rosenzweig et al. (1972),
Bouchard et al. (1990), and Harlow (1848), respectively.
Rosenzweig et al (1972)
Research Method: Experimental
Aim: To investigate the effect of either enrichment or
deprivation on the development of neurons in the
cerebral cortex of mice.
Procedure
 Rats were placed into one of two experimental
conditions: enriched environment or deprived
environment
 Enriched environment contained a variety of stimuli
for the rats (e.g. interesting toys); rats lived in
groups of 6-8
 Deprived environment was isolated, contained no
stimuli, or toys with which to play
 After 30 or 60 days in their respective environments,
the rats were sacrificed and post-mortem studies
were conducted on their brains
Findings
 Post-mortem studies revealed that rats in the
enriched environment condition had an increased
thickness in their cerebral cortex
 The frontal lobes (associated with thinking, planning,
and higher decision making) of rats from the
stimulated condition were heavier than those from
the rats in the deprived environment
 These findings strongly support the theory that brain
plasticity can be changed depending on an animal’s
environment
Conclusions
 Supports neuroplasticity (i.e. the brain’s ability to
rearrange connections between neurons);
environmental stimulation impacts learning, which
correlates to an increase of dendritic branching
Applications
 This study can only be generalized to humans to
some extent, as the environmental inputs and
genetic-makeup of humans differ. Psychologists
cannot carry out controlled experiments to test
this with humans as it is unethical.
Limitations
 The rats in the “deprived” experimental condition
of the experiment were purposely subjected to
extreme levels of mental stress for extended
periods of time; harm done to animals was
neither avoided nor minimized
 Cannot be completely generalized to humans as
their genetic makeup and environmental input
differs
 The rats’ mental stress due to isolation may
have been a potentially confounding variable
 Low ecological validity as it was a laboratory
experiment with an artificial environment
Evaluation
Strengths: Highlights the importance of
education in the growth of new synapses;
evidence of neuroplasticity
Harlow
Research Method: Case study
Aim: To investigate the effect of brain damage in
psychological processes.
Procedure
 Longitudinal case study of Phineas Gage, a railway
worker
 In 1848, during a violent explosion that resulted from
a railway accident, an iron rod flew through the air
and through Gage’s head. The rod entered below
his left cheek and exited through the top of his skull.
Gage was still conscious as he was rushed to the
hospital, where he was placed into the care of Dr.
Harlow
 Gage’s wounds healed, but there were significant
changes in his behaviour that were monitored
Applications
 Psychologists understood that the frontal lobe
had a specific function and realized that no part
of the brain is expendable.
 Future doctors and psychologists can realize
victims of brain damage will be affected in
particular ways and can better prepare for it
Evaluation
 Strength: Harlow’s study helped to demonstrate
localization of function, and led to research by
Paul Broca (1861) and Carl Wernicke (1874)
Findings
 Gage’s memory and other cognitive functions
remained intact, but there were significant changes
in his emotions and behavior
 Harlow described him as having little restraint, using
uncharacteristically rude language, and making
grand plans for the future which would be instantly
replaced with others
Conclusions
 The longitudinal study of the damage to his frontal
lobe provided evidence that the brain effects
personality and social behaviour
 Behaviour in the brain is localized and pertains to a
specific part of the brain
Limitations
 The extent of Gage’s brain damage is uncertain
 It is not possible to replicate the findings of the
study because it is unique to Phineas Gage; as
such, the reliability of the data can said to be
low
 Ethical considerations: Phineas Gage’s entire
life story was publicized and shared with the
world (no confidentiality or anonymity)
Bouchard et al. (1990)
Research Method: Correlational study
Aim: To investigate the role of genetics in determining
intelligence
Procedure
 Identical and fraternal twins were tested for
intelligence
 Groups of subjects included: identical twins reared
together, identical twins reared apart, fraternal twins
reared together, biological siblings reared together
 Each participant completed approximately 50 hours
of testing and interviews with researchers
 Results from each person’s testing were then
compared to their corresponding twin/sibling to
determine overlap in intelligence
Applications
The study helps to understand why adopted children
don’t always get along in their new home with their
adoptive family, and to understand why some children
don’t learn as well as others in similar environments
Evaluation
Strengths: Very high cross-cultural validity, with
participants recruited from all over the world. Mean age
of MZA (identical twins reared apart) was 41 years at the
start of the study, resulting in high generalization.
Findings
 The concordance (i.e. agreement) rates of
intelligence are as follows:
 Same person tested twice: 87%
 Identical twins raised together: 86%
 Identical twins reared apart: 76%
 Fraternal twins reared together: 55%
 Biological siblings reared together: 47%
Conclusions
 Researchers determined a heritability estimate of
~70% (i.e. 70% of intelligence can be attributed to
genetic inheritance)
 30% of intelligence can therefore be attributed to
other factors, such as environment
Limitations
 Relied on media coverage to recruit participants
 Ethical concerns about the way he reunited the
twins raised apart (i.e. protection from mental or
emotional stress)
 No control to monitor the frequency of contact
between the twins prior to the study
 It cannot be assumed that twins raised together
experienced identical environments; “equal
environment assumption”
 Correlation does not imply causation

Experimental Method
Strengths
 Establishes a cause-and-effect relationship
 High replicability and reliability
 All variables are controlled
 Generates certain quantitative data
Case Study
Strengths
 Provides very rich and detailed data
 Qualitative observations tend to be much more indepth and insightful
 Longitudinal studies measure behavior over an
extended period of time
 Allows researchers to study variables that could not
otherwise be recreated in a lab due to ethical
restrictions
Correlational Study
Strengths
 Objective way to determine the strength and
direction of a relationship between two variables
 Quantitative data is normally very rich and detailed
 Correlational studies make it possible to survey a
large sample at once, increasing generalization
Limitations
 Artificiality in laboratory experiments
 Extraneous and confounding variables are possible
 Demand characteristics are possible
 Researcher bias is possible
Limitations
 Often low generalization of the results back of the
lack of participant variability
 Usually low replicability because of the unique
conditions affecting the participants
 Results can be susceptible to researcher bias
 Ethical issues relating to confidentiality, deception,
invasion of privacy
Limitations
 Bidirectional ambiguity is possible – when it is
uncertain which variable caused the other (whether
x caused y or y caused x)
 No cause-and-effect relationship can be established
 Interpretation of data can be susceptible to
researcher bias