The Theory of Planned Behaviour

7/29/2019 The Theory of Planned Behaviour

1/54

The Theory of PlannedBehaviour


2/54

The Theory of Reasoned Action (TRA)

TRA posits that individual behaviour is driven by behavioural intentions wherebehavioural intentions are a function of an individual's attitude toward thebehaviour and subjective norms surrounding the performance of the behaviour.

Attitude toward the behaviour is defined as the individual's positive or negativefeelings about performing a behaviour. It is determined through an assessment ofone's beliefs regarding the consequences arising from a behaviour and anevaluation of the desirability of these consequences. Formally, overall attitude canbe assessed as the sum of the individual consequence x desirability assessments

for all expected consequences of the behaviour.

Subjective norm is defined as an individual's perception of whether peopleimportant to the individual think the behaviour should be performed. Thecontribution of the opinion of any given referent is weighted by the motivation that

an individual has to comply with the wishes of that referent. Hence, overallsubjective norm can be expressed as the sum of the individual perception xmotivation assessments for all relevant referents.


3/54

Core Assumptions and Statements

Theory of Reasoned Action suggests that a person's behaviour is determinedby his/her intention to perform the behaviour and that this intention is, in turn, afunction of his/her attitude toward the behaviour and his/her subjective norm.

The best predictor of behaviour is intention. Intention is the cognitive

representation of a person's readiness to perform a given behaviour, and it isconsidered to be the immediate antecedent of behaviour.

This intention is determined by three things: their attitude toward the specificbehaviour, their subjective norms and their perceived behavioural control.

The theory of planned behaviour holds that only specific attitudes toward thebehaviour in question can be expected to predict that behaviour. In addition tomeasuring attitudes toward the behaviour, we also need to measure peoplessubjective norms their beliefs about how people they care about will view the

behaviour in question.


4/54

To predict someones intentions, knowing these beliefs can be as important as

knowing the persons attitudes.

Finally, perceived behavioural control influences intentions. Perceived behaviouralcontrol refers to people's perceptions of their ability to perform a given behaviour.These predictors lead to intention.

A general rule, the more favourable the attitude and the subjective norm, and thegreater the perceived control the stronger should the persons intention to performthe behaviour in question.


5/54


6/54

B = BehaviourB1 = Behavioural intentionAB = Attitude toward behaviourSN = Subjective NormW1 & W2 = Weights

The model has some limitations including a significant risk of confoundingbetween attitudes and norms since attitudes can often be reframed as norms andvice versa. A second limitation is the assumption that when someone forms an

intention to act, they will be free to act without limitation.

In practice, constraints such as limited ability, time, environmental ororganisational limits, and unconscious habits will limit the freedom to act. Thetheory of planned behaviour (TPB) attempts to resolve this limitation.

1 1 2w AB w SN = +


7/54

Technology Acceptance Model (TAM)

TAM is an adaptation of the Theory of Reasoned Action (TRA) to the field of IS.TAM posits that perceived usefulness and perceived ease of use determine anindividual's intention to use a system with intention to use serving as a mediator ofactual system use. Perceived usefulness is also seen as being directly impacted

by perceived ease of use.

Researchers have simplified TAM by removing the attitude construct found in TRAfrom the current specification (Venkatesh et. al., 2003).

Attempts to extend TAM have generally taken one of three approaches: byintroducing factors from related models, by introducing additional or alternativebelief factors, and by examining antecedents and moderators of perceivedusefulness and perceived ease of use (Wixom and Todd, 2005).


8/54


9/54

TRA and TAM, both of which have strong behavioural elements, assume that

when someone forms an intention to act, that they will be free to act withoutlimitation.

In practice constraints such as limited ability, time, environmental ororganisational limits, and unconscious habits will limit the freedom to act.


10/54

How the Theory of Planned Behaviour Works

The theory of planned behaviour (TPB) was developed by Ajzen in 1988. The theoryproposes a model which can measure how human actions are guided. It predicts theoccurrence of a particular behaviour, provided that behaviour is intentional.

The model is out lined in the next figure and represents the three variables which thetheory suggests will predict the intention to perform a behaviour. The intentions are theprecursors of behaviour.


11/54

Ajzen and Fishbein formulated in 1980 the theory of reasoned action (TRA). This

resulted from attitude research from the Expectancy Value Models. Ajzen and Fishbeinformulated the TRA after trying to estimate the discrepancy between attitude andbehaviour.

This TRA was related to voluntary behaviour. Later on behaviour appeared not to be100% voluntary and under control, this resulted in the addition of perceived behaviouralcontrol. With this addition the theory was called the theory of planned behaviour (TpB).

The theory of planned behaviour is a theory which predicts deliberate behaviour,because behaviour can be deliberative and planned.


12/54


13/54

The variable names in the model reflect psychological constructs and so they have

meaning within the theory.

Behaviour

In implementation research, interventions are designed to change the behaviour of

individuals. The target behaviour should be defined carefully in terms of its Target,Action and Time.

In a transport context this is the target is the commuter, action is the trip, context is thetype of trip and time is the time taken to travel.

Intention

Although there is not a perfect relationship between behavioural intention and actualbehaviour, intention can be used a proxy measure of behaviour. This observation isone of the most important contributions of the TPB model compared to previousmodels of the attitude-behaviour relationship.


14/54

Therefore, the variables in this model can be used to determine the effectiveness of

the implementation interventions even if there is not a readily measure of actualbehaviour.

Attitudes towards the behaviour

Attitude toward the behaviour is a persons overall evaluation of the behaviour. It isassumed to have two components which work together: beliefs about consequencesof the behaviour (behavioural beliefs: by providing a new LRT system it will increasepublic transport trips) and the corresponding positive or negative judgements abouteach of these features of the behaviour (outcome evaluations: decreasing car trips is

desirable).

Subjective Norms (about the behaviour)

Subjective norms are a persons own estimate of the social pressure to perform thetarget behaviour. Subjective norms are assumed to have two components whichwork in interaction: beliefs about how other people, who may be in some wayimportant to the person, would like them to behave (normative beliefs).


15/54

Perceived behavioural control

Perceived behavioural control is the extent to which a person feels able to enact thebehaviour. It has two aspects: how much a person has control over the behaviourand how confident a person feels about being able to perform or not perform thebehaviour. It is determined by control beliefs about the power of both situational andinternal factors to inhibit or facilitate the performing of the behaviour.

Direct measures and indirect (belief-based) measures

With the exception of behaviour, the variables in the TPB model are psychological

(internal) constructs. Each predictor variable may be measured directly e.g. byasking respondents about specific behavioural beliefs and outcome evaluations.Direct and indirect measurement approaches make different assumptions about theunderlying cognitive structures and neither approach is perfect.

When different methods are tapping the same construct, scores are expected to bepositively correlated, so it is recommended that both be included in TPBquestionnaires.


16/54

Reliability

It is important to establish the reliability of each measure. For direct measures,one form of reliability may be established using an index of internal consistency(to determine whether the items in the scale are measuring the same construct).However, because people can quite logically hold both positive and negativebeliefs about the same behaviour, it is not appropriate to assess the reliability of

indirect measures using an internal consistency criterion.


17/54

Steps in the construction of a TRB Questionnaire

The construction of a questionnaire to measure the variables in the TPB modeproceeds in nine phases:

1. Define the population of interest, decide how best to select a representative

sample from this population.

2. Carefully define the behaviour under study, using the TACT principle.

3. Decide how best to measure intentions.

4. Determine the most frequently perceived advantages and disadvantages of

performing the behaviour

5. Determine the most important people or groups of people who would approveor disapprove of the behaviour


18/54

6. Determine the perceived barriers or facilitating factors which could make iteasier or more difficult to adopt the behaviour.

7. For a standard TBP-based study, include items to measure all of theseconstructs in the first draft of the questionnaire.

8. Pilot test the draft and reword items if necessary.

9. Assess the test-retest reliability of the indirect measures by administering the

questionnaire twice to the same group of people, with an interval of at leasttwo weeks.


19/54

Measuring Behavioural Intentions

Typically there are three methods of measuring behavioural intentions.

Method 1: Intention performance

This first method is used in situations where in some situations where it is

possible to observe actual behaviour.

Method 2: Generalised intention

This is the most commonly used method, whereby when investigating thebehaviour where multiple options are possible.

Method 3: Intention simulation

This method uses scenarios for respondents to evaluate and make choices basedupon the information provided. This is similar to a discrete choice method.


20/54

Measuring Attitudes

Direct measurement of attitude

Method

- Direct measurement involves the use of bipolar adjectives (very good very

poor).- Ideally use about four items following a single stem which identifies the

behaviour under investigation. For example, measuring the uses of publictransport based upon aspects of the service such as frequency, comfort etc.

- Use a good bad good scale to provide an evaluation method.


21/54

Scoring

- Recode the items that have negatively worded endpoints on the right so thathigher numbers always reflect a positive attitude to the target behaviour.

- It is important that the attitude items have high internal consistency, i.e. scoreson these items correlate highly with each other.

- Calculate the mean of the item scores to give an overall attitude score.

Indirect measurement of attitude: measuring behavioural beliefs andoutcome evaluations

Stages of development:

Conduct and elicitation study

- Take a sample from the population from which you will select respondents forthe questionnaire study.

- Use open-ended questions. These are normally presented in one-to-oneinterviews, but could also be in focus group or questionnaire form.


22/54

- Content analyse the responses into themes (behavioural beliefs) and label thethemes extracted. To increase the validity of the analysis, at least two

researchers should do this independently.- Using this method you ask the respondents to list the benefits of a given good

or service.


23/54

Measuring Subjective Norms

Procedure

- Direct measurement involves the use of questions referring to the options ofimportant people in general

- Use the first three items in the format below

- Where the response format completes an otherwise incomplete sentence

Scoring:

- Recode the items that have negatively worded endpoints on the right, so thathigh scores then consistently reflect greater social pressure to do the targetbehaviour


24/54

- It is important that the subjective norm items have high internal consistency,i.e. that the scores on these items correlate highly with each other.

- Calculate the mean of the item scores to give an overall subjective normscore.


25/54

Measuring Perceived Behavioural Control

- Items should reflect peoples confidence that they are capable of performing

the target behaviour. This can be achieved assessing the persons selfefficacy and their beliefs about the controllability of the behaviour.

- Self-efficacy is assessed by asking people to report

- How difficult it is to perform the behaviour

- How confident they are that they could do it.

-Controllability is assessed by asking people to report

-Whether performing the behaviour is up to them

- whether factors beyond their control determine their behaviour

- Remember that where the response format completes an otherwise incompletesentence, arrange the items so that the ends of the scales are a mix of positive andnegative end points.


26/54

Scoring

- Recode the items that have negative endpoints on the right, so that scoresthen consistently reflect a greater level of control over the target behaviour.

- It is important that the subjective norm items have high internal consistency,i.e. that scores correlate highly with each other.

- Calculate the mean of the item scores to give an overall perceived behaviouralcontrol score.


27/54

Changing Speeding Behaviour in Scotland: The 'Foolsspeed' campaign

'Foolsspeed' is a five-year campaign by the Scottish Road Safety Campaigndesigned to reduce the use of inappropriate and excessive speed on Scotland'sroads.

A major component of the campaign is a focused and structured mass mediacampaign underpinned by the Theory of Planned Behaviour (TPB) (Ajzen1988), a model which explains and predicts behaviour in terms of keypsychological determinants.

The TPB was used to shape a series of television advertisements, each

designed to address a key determinant of behavioural intention according to theTPB: attitudes, subjective norms and perceived behavioural control.

In November 1998 a series of six 10-second television advertisements

introduced the campaign logo and key messages. These were accompanied bypublicity materials and unpaid publicity activity to create widespread exposureto the campaign logo, thereby reinforcing the television advertising.


28/54

The 2 nd phase of the campaign in 1999 comprised a 40-second televisionadvertisement, "Mirror", designed to address attitudes regarding speeding and

speed choice.

The 3 rd phase of the campaign, in 2000, comprised a 40-second televisionadvertisement, "Friends and Family", which was designed to address

subjective norms in relation to speeding.

A 4 th phase in 2001 featured a television advertisement, "Simon Says",designed to address the third main component of TPB, perceived behavioural

control.


29/54

The 1999 "Mirror" Advert: AttitudesThe first advert was designed to address the attitudes component of the Theory

of Planned Behaviour. It sought to challenge the beliefs that speeding in townsaves time, that a speeding driver is fully in control of the car, and that he or sheis able to stop quickly in an emergency if necessary.

Beliefs about inappropriate speed (as opposed to excessive) speeding were

challenged by demonstrating that 30mph, although the legal speed limit may betoo fast in certain circumstances. The advertisement also sought to challengethe more general belief 'I'm a better driver than most'.

The 2000 "Friends and Family" Advert: Subjective Norms

The second advert, in Spring 2000, was designed to address the subjectivenorms component of the Theory of Planned Behaviour. This concerns drivers'perceptions of how much significant others in their lives would approve ordisapprove of their speeding, combined with their level of motivation to drive ina way that would meet the approval of these significant others.


30/54

The 2001 "Simon Says" Advert: Perceived Behavioural ControlThe third advertisement of the campaign was designed to address perceived

behavioural control - that is, drivers' perceptions of how easy or difficult it is toincrease their control over their speeding. This was possibly the most difficult ofthe TPB components to translate into advertising. The creative brief for theadvertising postulated that the advertisement should seek to challenge driverswith the sentiment 'you're responsible for the way you drive', by depicting typical

internal and external pressures which encourage drivers to speed anddemonstrating that it is possible and desirable to withstand such pressures.


31/54

Evaluation of the Foolsspeed Project

Foolsspeed was evaluated using a three-year longitudinal survey with a sampleof 550 drivers in the west of Scotland. A baseline survey was conducted inOctober 1998, before the start of the Foolsspeed campaign, and took measuresof respondents' demographic and driving characteristics and of the full raft ofTheory of Planned Behaviour components.

Follow-up surveys with the same sample were conducted in Spring 1999,Spring 2000 and Summer 2001.

These follow-up surveys repeated the measures taken at the baseline survey,

and also assessed response to the Foolsspeed campaign in terms ofawareness, recall, comprehension, identification, involvement and perceptionsof key messages.


32/54

Questionnaire MeasuresThe baseline questionnaire took measures of driver attitudes, subjective norms,

perceived behavioural control, intentions and reported speeding behaviour, inaccordance with the Theory of Planned Behaviour.

The questionnaire also included questions about driving behaviour such asmileage, length of time qualified, and frequency, purpose and destination of

journeys.

This allowed the possibility of analysing, at a future stage, variations betweendifferent types of driver (e.g. social drivers versus those who drive for a living,heavy road users versus light road users, newer drivers versus more

experienced drivers, and so on), as well as between different socio-demographic groups.

Behavioural intentions

These were measured using three statements: 'I would probably drive fasterthan 30mph myself in this situation', 'I would never drive faster than 30mph inthis situation', and 'In this situation I would want to driver faster than 30mph'.Reliability analysis showed that these items were highly consistent


33/54

Behavioural beliefs

On possible consequences (both good and bad) of speeding in the scenariodescribed were used in the survey. Speeding was defined as driving at 40mphin the situation described. The eight behavioural beliefs were identified from thequestionnaire piloting exercise and also from other studies.

Respondents were asked to indicate how likely or unlikely they judged each ofthe consequences (e.g. 'If I drove down this road at 40 mph I would find itdifficult to stop in an emergency'). Reliability for the behavioural belief items wasrelatively high (alpha=0.71).

Outcome evaluations

These were measured using eight statements corresponding to the behaviouralbelief statements. For these, respondents were invited to indicate how desirableor undesirable each outcome would be (e.g. 'Finding it difficult to stop in an

emergency would be').

These two sets of items were summed using the TPB formula to produce acomposite attitude towards the behaviour. Reliability for the outcome evaluationitems was adequate (alpha=0.60).


34/54

Normative beliefs

Were measured with eleven items in which respondents were asked to indicatehow much various significant others (or 'salient referents') would approve ordisapprove of their speeding (i.e. driving at 40mph) in the scenario described.Again, these salient referents were identified from the piloting exercise and fromprevious studies (e.g. Parker et al 1992).

Motivation to comply was assessed by asking respondents to indicate theextent to which they generally liked to drive in a manner of which each referentwould approve. These two sets of items were summed using the TPB formula toproduce a composite subjective norm score. Reliabilities for the two sets of

items were high (normative beliefs: alpha=0.70, motivation to comply:alpha=0.85, when missing values were recoded to the mid-point of the scale.Missing values occurred when respondents rated a particular referent 'notrelevant to me').


35/54

Perceived behavioural control

Was measured by asking respondents whether, in eight differentcircumstances, they believed they would be more or less likely to speed (forexample, 'Would you be more or less likely to drive down this road at 40mph ifyou were running late for an appointment?'). A corresponding eight items askedrespondents how often they found themselves in such circumstances when

driving.

These two sets of items, labelled control beliefsand control frequency, weresummed to produce a composite perceived behavioural control. An alternativesimpler measure of perceived behavioural control was also obtained, using two

items, 'I would find it frustrating to stick to 30mph in this situation' and 'I wouldfind it easy to stick to 30mph in this situation'.

These two measures of control were used because there appears, as yet, onlylimited consensus on how control should be operationalised within the TPB.

Reliability was high for the control beliefs (alpha=0.88) but low for the controlfrequencies (alpha=0.31). Reliability for the alternative measure of perceivedbehavioural control was high (alpha=0.80).


36/54

Samples examine


37/54


38/54


39/54


40/54


41/54


42/54


43/54

Drivers decision to speed: A study inspired by the theory of plannedbehaviour

Source: Drivers decision to speed: A study inspired by the theory of plannedbehaviorTransportation Research Part F: Traffic Psychology and Behaviour, Volume 9,Issue 6, November 2006, Pages 427-433, Henriette Walln Warner and Lars

berg

This study was completed in Sweden, where between 1999 and 2002 to testdrivers reactions to speeding. The study used an intelligent speed adoptiondevice to inform drivers of speeding.

The device was installed in the car for a month with no warnings activated tomeasure current behaviour of drivers. When the drivers were in the range of adigital map they were logged and measured to see if they were speeding.

All of the respondents were surveyed to ascertain their attitudes to speedingetc.

Th l f h d i l h i l i i


44/54

The results of the surveys were measured using a polychoric correlation matrix.This is a method of analysis which looks at opinions and creates a correlation

matrix based upon examining this correlation.


45/54


46/54

Measuring cognitive determinants of speeding: An application of the


47/54

Measuring cognitive determinants of speeding: An application of thetheory of planned behaviour

Source: Measuring cognitive determinants of speeding: An application of thetheory of planned behaviourTransportation Research Part F: Traffic Psychology and Behaviour, HelmutParis and Stephan Van den Broucke

This is a study which was conducted in Belgium.


48/54


49/54


50/54

Past exam questions


51/54

Past exam questions

2004

Past exam questions


52/54

Past exam questions

2003

Past exam questions


53/54

q

2002

Past exam questions


54/54

q

2001

The Theory of Planned Behaviour

Documents

Transcript of The Theory of Planned Behaviour