Lecture 1: Theories of planned behaviour
Health communication
- Increased number chronic diseases
- Health behaviour important predictor
- Health behaviour in need of change because people don’t exercise, smoke, drink and
eat unhealthy food
Theory
- Set of statements about relationship between tow or more concepts or constructs
- Concept/constructs are the building blocks of understanding
o Generalized abstraction
o Learned
o Functional
Explanation and prediction
- Prediction → predict that something is going to happen in the future on the basis of
pre-happenings → not necessarily understanding why things happen
- Explanation → more specific understanding
- Understanding in scientific sense→ identify, describe, predict and explain
Scientific approach→ conceptual constructs bring empirical reality together
- Conceptual realm → concepts and their relations
- Empirical realm → concept and relation assessed in guided approach
- Theoretical propositions subjected empirical test
Good theory
1. Utility
2. Acceptance by multiple scientists
3. Consistent with other theories
4. Range of theory
5. Creativity
- In need data for trying to confirm the propositions
Why is theory useful
- Why do or don’t people take action
- Explain behaviour and suggest how to change it
- Pinpoint what you need to know before developing programs
o How to shape effective programs
- What should be monitored and measured & compared in evaluation
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,Causality
- Causality for indicating changes → x is cause of y if changes in x produce changes in
y
- Discussed because causality is hard to proof but useful for thinking about the world
- Identify systematic relationships between variables
- Causal thinking→ therapy for health-related problems
Types of relations between concepts
1. Direct causal relationship
o Given cause (x) direct causal effect on outcome variable (y)
o E.g. parental communication on smoking behaviour
2. Mediated (indirect) causal relationship
o Variable (x) influences another variable (y) indirect through intermediary
variable (z)
o Z is mediator → work through to influence the outcome
o How come x is related to y
o E.g. Tv exposure indirectly related to being overweight because tv exposure
directly related to eating snacks
3. Moderated causal relationship
o Causal relationship between two variables differs depending on value third
variable
o Outcome can explain for one specific value of third variable
o Under which circumstances does x influence y
o E.g. medication influences decrease of headache but only for women
4. Spurious causal relationship
o Relationship between variables because of sharing common cause not because
one influences the other
o E.g. shoe size and verbality →actually explained by age
o Use statistics for finding the spurious relations
Specifying conceptual definitions
- Literature and dictionaries
- TACT→ key properties construct
1. Target → who
2. Action → what
3. Context → where
4. Time → when
Theory of reasoned action (Fishbein)
- Understanding people’s decisions in health behaviour must consider:
o Attitude → expectancies advantages and disadvantages
o Subjective norm → normative pressure
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, o These will tell us why people behave in a certain way
- Intention is the best predictor for behaviour
o Sometimes used for measuring behaviour
- Attitudes and subjective norm predict intention and therefore behaviour
o Attitude → what do you expect
Behavioural beliefs → what are disadvantages and advantages
Behavioural outcomes → importance of disadvantages and advantages
o Subjective norm→ is behaviour compliant or does it matter
Normative beliefs→ what others tell you what’s good or bad
Motivation to comply → what you feel you should do
- These single constructs make sets of constructs
- Mediated relationship
Theory of planned behaviour (Ajzen)
- Adding value to the theory of reasoned action → not only attitude but also perceived
control
o Attitude → what do you expect
Behavioural beliefs → what are disadvantages and advantages
Behavioural outcomes → importance of disadvantages and advantages
o Subjective norm→ is behaviour compliant or does it matter
Normative beliefs→ what others tell you what’s good or bad
Motivation to comply → what you feel you should do
o Perceived control → perceptions of ability to perform behaviour
Control beliefs→ belief of existence of factor that will influence the
behaviour
Perceived power → how capable am I to perform the behaviour
- Perceived control also moderates the relation between intention and behaviour
Measurement
- Translating theory into empirical data
- Behaviour → 1-9 scale with endpoints
- Attitude → semantic differential (adjective pairs)
- Intention → 1-7 scale with statements
- Subjective norm → 1-9 scale with endpoints
- Perceived behavioural control → opposites with 1-7 scale
- Behavioural strength → 1-7 scale with statements
- Normative beliefs → 1-7 scale with statements
- Motivation to comply → 1-7 scale with statements
- Control beliefs → 1-7 scale with statements
- Consider what you want to measure and make the right statements, pairs and questions
→ all sorts of scales are useful as long you can explain your choice of measurement
Many health-related studies
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