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Lecture 2

PSY 302 Lecture Notes - Lecture 2: Inter-Rater Reliability, Twin Study, Selective Breeding

Course Code
PSY 302
Dana Williams

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Research Methods in Developmental Psychology
The Scientific Method
1. Problem or questions
2. Hypothesis or prediction
3. Devising a method and gathering data
4. Drawing conclusions
Gathering Data
Scientific measures must be directly relevant to the hypothesis being studied, reliable and valid
Reliable: Consistent info across time (test-retest reliability) and across observers (interrater
Validity: Measures what supposed to measure; internal (can you determine cause and effect from
the independent variable) + external validity
Different Ways to Measure Behaviour
1) Self-Report Methodologies
Structured interviews and questionnaires
Avantages: Large amounts of info, easy & quick, standardized results
Disadvantages: Can’t be used with young kids who can’t read/understand
language well, lying, social desirability, memory errors, do all ages understand
questions in the same way if comparing diff age groups, which persons reports
are the most accurate, what people say is not often what they do (Should ask
parents, teachers & children)
Clinical Interviews - Everyone asked same questions initially but you can dig deeper
Advantages: Large amount of info, fast & easy, more flexible, can get a rich
meaning of answers
Disadvantages: Not asked standardized questions so harder to compare subjects,
more likely to be biased and based on biased interpretations
2) Observational Methodologies
Naturalistic observation - Camera/person make observations while not being noticed
Advantages: Better for studying infants/toddlers who don’t have language, real-
Disadvantages: Reactivity, can’t determine cause and effect, unlikely to observe
very infrequent or socially undesirable behaviour, observer effects, people
respond differently in different real-life settings
Structured Observations - Design a situation and put participants in the same situation
Advantages: Can study behaviour less likely to occur in a natural environment,
more standardized so can compare people since all exposed to same stimulus
Disadvantages: Will they act this way in real life, how similar to real life is this,
can't get the in-depth results you’d get from interviews
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Detecting Relationships
1) Correlational Design: Used to determine if 2 variables are related, if you know one variable
you can predict the other, you cannot determine cause and effect, correlations range from -1 to 1
Advantages: Used for prediction and when an independent variable can’t be manipulated
Disadvantages: Direction of causation problem, 3rd variable problem
Positive Correlation: As one variable increases, the other increases
Negative Correlation: As one variable increases, the other decreases
0 Correlation: NO relationship
2) Experimental Design: Must have random assignment to large groups
I Variable - Manipulated Extraneous Variables - Held constant
D Variable - Measured Confounding Variable and - Extraneous variable not
Lab Experiment
Advantages: Determine cause and effect, high degree of control over the variables
Disadvantages: Will people act like this in real-life, is there external validity, can’t investigate
many topics where it’s impossible or unethical to manipulate an independent variable
Designs for Studying Development
1) The Cross-Sectional Design: People who different in age (different cohorts) are studied at the
same point in time
Cohorts: Born at the same time and experience the same socio-historical circumstances at
the same age
Advantages: Quick and easy
Disadvantages: Age effects confounded by cohort effects, tells us nothing about
individual development
2) The longitudinal Design: The same cohort is observed repeatedly over a period of time
Avantages: Can look at individual differences, the impacts of earlier events on later
behaviour, normative developmental trends that all children might share
Disadvantages: Costly, time consuming, studies may become outdated over time,
practice effects (improve from practice) , selective attrition, cross-generational
problem since the sample is only drawn from one cohort
3) The Microgenetic Design: Kids who are thought to be ready for an important developmental
change are exposed repeatedly to experience that are thought to produce the change and their
behaviour is monitored as it is changing, study participants over a period of hours/days/weeks
Advantages: Getting details on how a developmental change comes about
Disadvantages: Time consuming and costly to track large #s kids in such a manner,
practice effects so it’s best to research only changes that are known to occur at a
particular age then try to specify how/why
Ethical Consideration in Developmental Research
1. No physical or psychological harm
2. Informed consent of teacher, parents, school in writing
3. Children told they don’t have to participate or can quit at any time
4. Confidentiality (except for victims of child abuse)
5. If use deception, researchers must debrief participants
6. Ethical review committees in universities research hospitals
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