Introduction to Developmental Psychology
Studying Development Scientifically
Developmental psychology has two key aims:
1. To chart the course of development across the lifespan
2. To identify the causes of development
How do we know if one thing causes another?
What are developmental theories?
Developmental theories are a special form of causal or ‘functional’ relationship.
Conditions for establishing causal relationships
o Observed variables must co-vary (covariation)
o Covariation must not be spurious (non-spuriousness)
o Causal factors must precede outcomes (temporality)
Causal factors
Necessary Causal Factors
o Factors that must be present for an outcome to occur
Sufficient Causal Factors
o Factors that are by themselves enough to cause an outcome to occur.
It is impossible to develop tuberculosis without exposure to mycobacterium
tuberculosis (it is necessary). Not all people exposed to mycobacterium tuberculosis
develop tuberculosis (it is not sufficient).
Cross-Sectional Research
Research conducted at a single point in time
1. Comparing performance in different age groups
2. Describing patterns of relationships at a specific point in time
Beware developmental claims based on cross-sectional data
Zelazo et al. (2013) found substantial associations between age and performance on
two measures of executive function.
Due to it looking at different groups of children there could be other factors that
cause the change in development and not just the factor you are looking at.
Permissive parenting
may lead to children
having a lack of self-
control. They may
not set boundaries or
model the way it’s
supposed to be.
Also it may be a child
driven effect,
, meaning that the child’s lack of self-control leads to permissive parenting. For
example, if the child is running around all the while it may lead to the parents giving
up and leaving the child to do what they want.
However, there may be other factors that are not measured that may cause the
child’s lack of self-control or permissive parenting.
Can cross-sectional research advance developmental theory?
1. Says nothing about the cause of an individual’s development over time
2. Developmental or age effects are confounded by the possibility of cohort
effects – occurs when there is a difference between the two groups for some
other reason such as their backgrounds for example.
3. Cannot provide evidence about temporal ordering of cause and effect.
Longitudinal research
Research that measure the same individuals at more than one point in time.
o Studying the course of development
o Explaining the causes of development
Longitudinal research is appropriate when the focus is on the study of:
o Within-person change over time
o The (rank-order) stability of individual differences over time
o The causes of development
What type of study is needed?
o Three most common longitudinal designs:
Panel studies
Multiple cohort studies/cohort sequential studies
Intervention studies
o We don’t really use retrospective research which is where you already know
the outcome and ask people about the past. This is because it is subject to
many types of bias.
Panel or multiple cohort design?
o Panel studies can be used to provide evidence for maturational or
developmental changes.
o Period effects might also account for observed changed in performance in
panel studies.
o The strongest evidence for developmental change is when changes occur
across multiple cohorts.
Intervention studies
o Intervention studies are a form of experimental longitudinal studies
o They split the group up and give one group one type of exposure and the
other group another exposure and look at the difference in them over time
o Panel and multiple cohort studies provide an indication of developmental
causes
o Intervention studies show conclusively that one variable causes development
in another.
Studying Development Scientifically
Developmental psychology has two key aims:
1. To chart the course of development across the lifespan
2. To identify the causes of development
How do we know if one thing causes another?
What are developmental theories?
Developmental theories are a special form of causal or ‘functional’ relationship.
Conditions for establishing causal relationships
o Observed variables must co-vary (covariation)
o Covariation must not be spurious (non-spuriousness)
o Causal factors must precede outcomes (temporality)
Causal factors
Necessary Causal Factors
o Factors that must be present for an outcome to occur
Sufficient Causal Factors
o Factors that are by themselves enough to cause an outcome to occur.
It is impossible to develop tuberculosis without exposure to mycobacterium
tuberculosis (it is necessary). Not all people exposed to mycobacterium tuberculosis
develop tuberculosis (it is not sufficient).
Cross-Sectional Research
Research conducted at a single point in time
1. Comparing performance in different age groups
2. Describing patterns of relationships at a specific point in time
Beware developmental claims based on cross-sectional data
Zelazo et al. (2013) found substantial associations between age and performance on
two measures of executive function.
Due to it looking at different groups of children there could be other factors that
cause the change in development and not just the factor you are looking at.
Permissive parenting
may lead to children
having a lack of self-
control. They may
not set boundaries or
model the way it’s
supposed to be.
Also it may be a child
driven effect,
, meaning that the child’s lack of self-control leads to permissive parenting. For
example, if the child is running around all the while it may lead to the parents giving
up and leaving the child to do what they want.
However, there may be other factors that are not measured that may cause the
child’s lack of self-control or permissive parenting.
Can cross-sectional research advance developmental theory?
1. Says nothing about the cause of an individual’s development over time
2. Developmental or age effects are confounded by the possibility of cohort
effects – occurs when there is a difference between the two groups for some
other reason such as their backgrounds for example.
3. Cannot provide evidence about temporal ordering of cause and effect.
Longitudinal research
Research that measure the same individuals at more than one point in time.
o Studying the course of development
o Explaining the causes of development
Longitudinal research is appropriate when the focus is on the study of:
o Within-person change over time
o The (rank-order) stability of individual differences over time
o The causes of development
What type of study is needed?
o Three most common longitudinal designs:
Panel studies
Multiple cohort studies/cohort sequential studies
Intervention studies
o We don’t really use retrospective research which is where you already know
the outcome and ask people about the past. This is because it is subject to
many types of bias.
Panel or multiple cohort design?
o Panel studies can be used to provide evidence for maturational or
developmental changes.
o Period effects might also account for observed changed in performance in
panel studies.
o The strongest evidence for developmental change is when changes occur
across multiple cohorts.
Intervention studies
o Intervention studies are a form of experimental longitudinal studies
o They split the group up and give one group one type of exposure and the
other group another exposure and look at the difference in them over time
o Panel and multiple cohort studies provide an indication of developmental
causes
o Intervention studies show conclusively that one variable causes development
in another.
