Measurement of Constructs in Psychosocial Models of Health Behavior March 26, 2012 Neil Steers, Ph.D.
Importance of measurement in research testing psychosocial models Issues in measurement of psychosocial constructs (e.g. health-related beliefs, attitudes, perceptions) are often neglected research testing psychosocial models Appropriate measurement of psychosocial constructs in important for several reasons Hypotheses about associations between these constructs and behavior can only be tested meaningfully with reliable/valid measures of constructs Behavior change interventions target these constructs directly, and the impact of an intervention cannot be assessed without sound measures of constructs
Integrative model of health behavior Theory of Planned Behavior (Fishbein & Ajzen, 1991, 2010) Underlying beliefs Behavioral beliefs Attitude toward the behavior Central constructs Normative beliefs Perceived Norms Behavioral Intention Behavior Control beliefs Perceived behavioral control -self-efficacy Integrates constructs specified as determinants of health behavior from: The theory of reasoned action (Fishbein( & Ajzen,, 1975) The health belief model (Janz( & Becker, 1984) Social cognitive theory (Bandura( Bandura,, 1986)
Theory of planned behavior (TPB) Attitude toward the behavior Theory of Planned Behavior Central constructs Perceived Norms Behavioral Intention Behavior Perceived behavioral control Studies testing the TPB or its components typically focus on the central constructs and behavior The underlying beliefs are ignored or de-emphasized emphasized
Attitude toward the behavior definition and measurement Theory of Planned Behavior Attitude toward the behavior Perceived Norms Behavioral Intention Behavior Perceived behavioral control Attitude toward the behavior the degree to which the health behavior is positively or negatively valued Example behavior Exercising 20 minutes, three times per week for three months following heart surgery The measurement approach typically involves asking the respondent t indicate his/her favorability toward performing the behavior on several semantic s differential adjective scales.
Attitude toward the behavior definition and measurement My exercising for at least 20 minutes, three times per week for the next three months would be bad : 1 : 2 : 3 : 4 : 5 : 6 : 7 : good pleasant : 1 : 2 : 3 : 4 : 5 : 6 : 7 : unpleasant The Likert method can be used, but semantic differential is more widely used in research testing TPB
Perceived norm definition and Attitude toward the behavior measurement Perceived Norms Behavioral Intention Behavior Perceived behavioral control Perceived norm perceived social pressure to perform or not to perform the health behavior. Two components Injunctive component perception of expectations held by other people to perform the behavior Descriptive component perception of whether other important/relevant people actually perform the behavior
Perceived norm definition and measurement Perceived norm items ask respondents to report perceptions that their generalized normative referent (e.g. important others, similar others) performs the health behavior, or expects them to perform the health behavior. Perceived norm: Injunctive and descriptive aspects Most people who are important to me approve of my exercising for at least 20 minutes, three times per week for the next three months. agree : 1 : 2 : 3 : 4 : 5 : 6 : 7 : disagree Most people like me exercised for at least 20 minutes, three times per week in the three months following their major heart surgery unlikely : 1 : 2 : 3 : 4 : 5 : 6 : 7 : likely
Perceived behavioral control definition and measurement Attitude toward the behavior Perceived Norms Behavioral Intention Behavior Perceived behavioral control Perceived behavioral control perception that one is capable of performing the behavior and it is under volitional control. Two components: Efficacy component perception that one is capable of performing the behavior (self-efficacy) efficacy) Control component perception of degree of control that one has over performing behavior
Perceived behavioral control definition and measurement Perceived behavioral control items ask people about whether they believe they are capable of performing the behavior (efficacy perceptions) whether they believe that doing so is completely under their control (control perceptions) Perceived behavioral control I am confident that I can exercise for at least 20 minutes, three times per week for the next three months. true : 1 : 2 : 3 : 4 : 5 : 6 : 7 : false My exercising for at least 20 minutes, three times per week for the next three months is up to me disagree: 1 : 2 : 3 : 4 : 5 : 6 : 7 : agree
Behavioral intention definition and measurement Attitude toward the behavior Perceived Norms Behavioral Intention Behavior Perceived behavioral control Behavioral intention indication of readiness and plan to perform behavior.
Behavioral intention definition and measurement Behavioral intention items instruct participant to directly report intentions Intention I intend to exercise for at least 20 minutes, three times per week for the next three months. true : 1 : 2 : 3 : 4 : 5 : 6 : 7 : false
Behavior definition and measurement Health behavior must be defined with respect to target, action, context, and time (TACT) Example: exercise behavior 20 minutes, 3 times per week for 3 months following heart surgery Target oneself, Action exercising, Context - at home/in community after release from hospital, Time 20 minutes, 3 times/week for 3 months Measures of all constructs must be compatible, or specific to the health behavior criterion of interest
Pilot testing the direct measures of central constructs See sample questionnaire containing direct measures of all central constructs in TPB Internal consistency reliability can be assessed Each subset of items measuring attitudes, perceived norms, perceived behavioral control and behavioral intention should have high Cronbach s alpha coefficients Items inconsistent with the remaining subsets can be eliminated or modified Cronbach Coefficient Alpha with Deleted Variable Cronbach Coefficient Alpha Deleted Variable Raw Variables Alpha Standardized Variables Alpha Variables Raw Standardized Alpha 0.75 0.76 AB1 AB2 AB3 AB4 0.76 0.78 0.91 0.77 0.78 0.79 0.90 0.80 AB attitude toward the behavior
Pilot testing the direct measures of Construct validity can also be assessed central constructs Confirmatory factor analysis should be used to test the fit between the data on items in each subset with the hypothesized four-factor factor latent structure AB attitude toward behavior PN perceived norm PBC perceived behavioral control BI behavioral intention Items: AB1 AB2 AB3 AB4 PN1 PN2 PN3 PN4 PBC1 PBC2 PBC3 PBC4 BI1 BI2 BI3 BI4 Factor 1: AB.80.90.85.75 Factor 2: PN.80.90.85.75 Factor 3: PBC.80.90.85.75 Factor 4: BI.80.90.85.75
Pilot testing the direct measures of central constructs Predictive validity of central constructs in TPB can also be tested Attitude toward the behavior Perceived Norms Behavioral Intention Perceived behavioral control
Limitations of studies focusing only on central constructs This cross-sectional sectional pilot study would evaluate the soundness of the direct measures of attitudes, norms, perceived behavioral control, and intention Buy focusing on just the central constructs, conclusions drawn from tests of the TPB would be limited Implication of associations between central constructs and intention/behavior - we can achieve health behavior change by modifying these constructs Information on how to target these constructs would be lacking There are more constructs in the TPB that should be measured and tested
Determinants of central constructs in TPB Theory of Planned Behavior Underlying beliefs Behavioral beliefs Attitude toward the behavior Central constructs Normative beliefs Perceived Norms Behavioral Intention Behavior Control beliefs Perceived behavioral control TPB proposes that the central constructs originate from beliefs Attitude toward the behavior is determined by behavioral beliefs Perceived norms are determined by normative beliefs Perceived behavioral control is determined by control beliefs These underlying beliefs should be measured and integrated into tests of the TPB
Expectancy/value determinants of central constructs Theory of Planned Behavior Underlying beliefs Behavioral beliefs Attitude toward the behavior Central constructs Normative beliefs Perceived Norms Behavioral Intention Behavior Control beliefs Perceived behavioral control TPB is one model in a class of psychosocial models of health behavior called expectancy/value models In expectancy/value models, key psychosocial constructs are believed to originate from expectancies, or beliefs, and by values of importance assigned to those beliefs
Expectancy/value determinants of attitude toward the behavior Theory of Planned Behavior Underlying beliefs Behavioral beliefs and outcome evaluations Attitude toward the behavior Central constructs Behavioral Intention Behavior Attitudes toward the behavior are determined by two expectancy/value factors Behavioral beliefs, or beliefs about the outcome of performing the behavior of interest (fast recovery) Example subjective probability that exercising 20 minutes per day will result in the outcome of faster recovery from surgery Outcome evaluation, or favorability of the expected outcome Example favorability toward faster recovery from surgery Favorability of faster recovery contributes to attitude toward exercising in direct proportion to subjective probability that exercising will result in faster recovery
Expectancy/value determinants of perceived norms Theory of Planned Behavior Underlying beliefs Central constructs Normative beliefs and motivation to comply Perceived Norms Behavioral Intention Behavior Perceived norms are determined by two expectancy/value factors Normative beliefs, or beliefs that a given normative referent expects the person to exercise 20 minutes a day following surgery (surgeon) Example subjective probability that one s s surgeon expects patient to exercise 20 minutes per day after surgery Level of motivation to comply with the expectations of normative referents Example level of importance one assigns to doing what one s s surgeon recommends Motivation to comply with surgeon contributes to perceived norm in direct proportion to subjective probability that surgeon expects patient to exercise
Expectancy/value determinants of perceived behavioral control Theory of Planned Behavior Underlying beliefs Central constructs Control beliefs and power of control perceptions Perceived behavioral control Behavioral Intention Behavior Perceived behavioral control determined by two expectancy/value factors Control beliefs, or belief that a control factor is present that makes performing the behavior easier or more difficult (physical strength) Example subjective probability that one will have the necessary physical strength to exercise 20 minutes per day after surgery Power of control factor, or perceived level of power that the control factor has over performance of the behavior Example perceived level of power that physical strength has as a factor necessary for exercising 20 minutes per day following surgery Perceived level of power of physical strength contributes to perceived behavioral control in direct proportion to subjective probability y that physical strength will be present
Measuring expectancy/value components of underlying beliefs Semantic differential items are used to measure expectancy/value components of attitudes toward the behavior, perceived norms, and perceived behavioral control Before constructing these items, it is necessary to determine Which behavioral outcomes are relevant to attitudes toward behavior Which normative referents are relevant to perceived norms Which control factors are relevant to perceived behavioral control
Importance of accessible beliefs According to expectancy/value theory, only those beliefs that are salient, or readily accessible in memory, affect the formation of attitudes, norms, and perceptions of behavioral control Only those behavioral outcomes (fast recovery) that are salient affect attitudes toward the behaviors Only those normative referents (surgeon) that are salient affect perceived norms Only those control factors (physical strength) that are salient affect perceptions of behavioral control Questionnaire items measuring behavioral, normative, and control beliefs must specify the relevant salient beliefs
How do we learn what the accessible and salient beliefs are when constructing our belief measures? Conduct a belief elicitation study before constructing belief measures in which participants are asked to identify expected outcomes of performing behavior, relevant normative referents, control factors Can be integrated into focus group discussion Open-ended ended belief elicitation questions can be added to the pilot questionnaire in which respondents are asked to identify the factors specified above
Sample questions for eliciting behavioral beliefs relevant to formation of attitude toward behavior Behavioral outcomes (1) What do you see as the advantages of your exercising for at least 20 minutes, three times per week for the next three months? (2) What do you see as the disadvantages of your exercising for at least 20 minutes, three times per week for the next three months? (3) What else comes to mind when you think about exercising for at least 20 minutes, three times per week for the next three months? Responses are analyzed for most frequently occurring expected behavioral outcomes
Items measuring behavioral beliefs are constructed specifying the elicited behavioral outcomes Behavioral Beliefs and Outcome Evaluations With respect to each salient behavioral outcome, items are formulated to assess the strength of the behavioral beliefs and the evaluation of the outcome. Sample Outcome: Losing weight Behavioral belief strength My exercising for at least 20 minutes, three times per week for the next three months will help me to lose weight. likely : 1 : 2 : 3 : 4 : 5 : 6 : 7 : unlikely Outcome evaluation My losing weight is good : 1 : 2 : 3 : 4 : 5 : 6 : 7 : bad
Sample questions for eliciting normative beliefs relevant to formation of perceived norms Normative referents When it comes to your exercising for at least 20 minutes, three times per week for the next three months, there might be individuals or groups who would think you should or should not perform this behavior. (1) Please list the individuals or groups who would approve or think you should exercise for at least 20 minutes, three times per week for the next three months. (2) Please list the individuals or groups who would disapprove or think you should not exercise for at least 20 minutes, three times per week for the next three months. (3) Sometimes, when we are not sure what to do, we look to see what others are doing. Please list the individuals or groups who, after major heart surgery, are most likely to exercise for at least 20 min, three times per week for the three months following surgery. (4) Please list the individuals or groups who, after major heart surgery, are least likely to exercise for at least 20 min, three times per week for the three months following surgery.
Items measuring normative beliefs are constructed specifying the elicited normative referents Sample normative referent: My spouse/partner Normative belief strength My spouse or partner thinks that I should : 1 : 2 : 3 : 4 : 5 : 6 : 7 : I should not exercise for at least 20 min, three times per week for the next three months. Motivation to comply When it comes to matters of health, I want to do what my spouse or partner thinks I should do. agree : 1 : 2 : 3 : 4 : 5 : 6 : 7 : disagree
Sample questions for eliciting control factors relevant to formation of perceived behavioral control Control factors (1) Please list any factors or circumstances that would make it easy or enable you to exercise for at least 20 min, three times per week for the next three months. (2) Please list any factors or circumstances that would make it difficult or prevent you from exercising for at least 20 min, three times per week for the next three months.
Items measuring control beliefs are constructed specifying the elicited control factors Sample control factor: Getting physical therapy Control belief strength I expect that I will get physical therapy in the next three months. likely : 1 : 2 : 3 : 4 : 5 : 6 : 7 : unlikely Power of control factor Getting physical therapy would enable me to exercise for at least 20 min, three times per week for the next three months. disagree : 1 : 2 : 3 : 4 : 5 : 6 : 7 : agree
How do we score expectancy/value- based belief measures? Scores on all measures of underlying beliefs are obtained by multiplying the response to a salient belief strength (expectancy) item by its corresponding value item, and summing the products across pairs of items
How do we score expectancy/value- based belief measures? See questionnaire Behavioral belief composite score = Σ (Q1 * Q7) + (Q2 * Q8) + (Q3 * Q9) + (Q4 * Q10) + (Q5 * Q11) + (Q6 * Q12) Normative belief composite score = Σ (Q13 * Q17) + (Q14 * Q18) + (Q15 * Q19) + (Q16 * Q20) + (Q21 * Q24) + (Q22 * Q25) + (Q23 * Q26) Control belief composite score = (Q27 * Q31) + (Q28 * Q32) + (Q29 * Q33) + (Q30 * Q34)
Testing belief composite associations Theory of Planned Behavior Underlying beliefs Behavioral beliefs and outcome evaluations Attitude toward the behavior Central constructs Normative beliefs and motivation to comply Perceived Norms Behavioral Intention Behavior Control beliefs and power of control perceptions Perceived behavioral control Behavioral belief composite should correlate highly with direct measure of attitude toward behavior Normative belief composite should correlate highly with direct measure of perceived norm Control belief composite should correlate highly with direct measure of perceived behavioral control
Why is measuring expectancy/value- based beliefs important? Underlying assumptions of the TPB and expectancy/ value theory are evaluated by testing associations between: behavioral belief composites and attitudes toward behavior normative belief composite and perceived norm control belief composite and perceived behavioral control tests If tests of these associations yield high correlations as expected, there is evidence that the elicitation of relevant beliefs was successful Elicited behavioral beliefs specify targets for behavior change interventions
Theory of Planned Behavior Underlying beliefs Behavioral beliefs and outcome evaluations Attitude toward the behavior Central constructs Normative beliefs and motivation to comply Perceived Norms Behavioral Intention Behavior Control beliefs and power of control perceptions Perceived behavioral control If any/all of the central constructs predict intention and in turn, behavior, the implication is that we can change intention and behavior by modifying attitudes, perceived norms, and/or perceptions of behavioral control How do we modify attitudes, perceived norms, and/or perceived behavioral control? We target the salient behavioral, normative, and or control beliefs efs that were elicited during the elicitation phase of our pilot work
Two phases of questionnaire administration are recommended in pilot work. Phase 1: Include direct measures of attitudes, norms, and perceived behavioral control, behavioral intention and past behavior (see phase 1 questionnaire) Assess reliability and validity of direct measures using Cronbach s alpha and confirmatory factor analysis Test predictive validity of central constructs in TPB Also include open-ended ended salient belief elicitation questions (see phase 1 questionnaire) Analyze open-ended ended responses to belief elicitation questions in order to isolate the most salient beliefs Construct items measuring salient beliefs to be included in second questionnaire
Phase 2 pilot questionnaire In phase 2, include direct measures attitudes, norms, and perceived behavioral control, behavioral intention and behavior (see phase 2 questionnaire) This will allow you to re-evaluate evaluate reliability and validity on modified item set This will also allow you to re-test the predictive validity of the central constructs
Phase 2 pilot questionnaire Also include expectancy/value-based salient belief items constructed from responses to elicitation questions (see phase 2 questionnaire) Test associations between 1) behavioral belief composite and attitudes toward behavior, 2) normative belief composite and perceived norms, and 3) control belief composite and perceived behavioral control If direct measures of constructs are found to predict intention/behavior, implication is that intervention targeting salient beliefs associated with constructs that predict intention/behavior would be successful in modifying intention and behavior
Brief conclusions Although issues with measurement of psychosocial constructs are often neglected, careful attention to theory when constructing measures of psychosocial constructs will result in several benefits: It helps to ensure high levels of reliability and validity Also helps to ensure high levels of predictive validity of the full model Allows you to test the basic propositions of the theory It helps to ensure that the results will be useful in the design of behavior change interventions targeting psychosocial constructs
Some useful references/information sources Fishbein,, M. & Ajzen,, I. (2010). Predicting and changing behavior: The reasoned action approach.. New York: Psychology Press. Icek Ajzen s website: http://people.umass.edu/aizen/tpb.html This page in particular has excellent information on measurement scale construction and intervention design Other links to websites offering information on construction of scales measuring psychosocial constructs http://pages.bangor.ac.uk/~pes004/exercise_psych/downloads /tpb_manual.pdf
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