Developmental Psychology: Research Issues Intractable Variables

1. Developmental Psychology: Research Issues • Intractable Variables • Difficult or impossible to manipulate • Heredity/Genes • Environment • Age • Age is a “proxy” for causal variables—i.e., age co-varies with these causal agents, but it is not a causal variable

2. Measurement Equivalence • When constructs change with development, measures that are appropriate at one age (time) may be inappropriate at another age • Ex: Assessment of attachment in preschoolers • Is a separation-reunion procedure appropriate?

3. Self-report data are limited • Parents, teachers, and other adults often complete “self-report” measures of children’s behavior • Greater reliance on observational techniques • Inferring the meaning of behavior is difficult • Ex: Infants’ understanding of object permanence

4. Complexity of causal influences • Ethical concerns preclude manipulation of many variables • Ex: maltreatment and children’s development • Laboratory analog studies may compromise external validity • Ex: Marital conflict and children’s development

5. Direction of causation • Biases/assumptions about the direction of influence • Ex: parents influence children rather than the reverse • Bidirectional influences are more likely than unidirectional influences

6. General Research Designs • Experimental Designs • Manipulation of hypothesized independent variable • Random assignment of participants to different conditions (between-subjects designs) OR other control procedures (within-subjects designs, small-n designs) • Allow strong inferences about causal relationships

7. Potential Limitations of Experimental Designs • Participant non-compliance in the “treatment” or “intervention” condition (e.g., dropping out, failure to participate fully in the treatment) • Generalization (external validity)

8. Non-experimental (Correlational) Designs • No manipulation of variables • No random assignment or other comparable control procedures • Not possible to make strong causal inferences

9. Why not? • Selection Bias (Confounding Variables) • Refers to third variables that are correlated with both the predictor variable and the outcome variable • Ex: Does high-quality child care cause improved school readiness? • Children in high-quality child care (and their families) are likely to be different in many ways from children in lower-quality child care (socioeconomic status; high-quality parental care) • These “confounding” variables are likely to be related to school readiness

10. Most common approach to reducing selection bias: • Identify, measure, and control for possible confounding variables either in the research design or in the statistical analysis

11. Developmental Designs • Designs in which age-related change is examined • Normative development (developmental functions) • Individual differences

12. Variables Involved in Developmental Designs • Cohort: Groups of participants who are born or experience some other common event in the same time period • Ex: children born in 1980 are a cohort; individuals growing up during the Great Depression are also a cohort • Age • Time/Point of Assessment

13. Simple Developmental Designs • Longitudinal Designs • A single cohort is examined at multiple ages (and thus at multiple times of assessment) • Age and time of assessment are confounded • An event may occur between points of assessment that produces differences in the dependent variable • Ex: Sept. 11 may affect rates of psychological disorders in children • If we see increases in psychological disorders in a longitudinal design, are they due to age or to time of assessment differences?

14. Advantages • Can examine stability and change in individual children’s characteristics and behavior over time

15. Disadvantages • Non-random participant loss (selective attrition) • Participants who finish the study differ in systematic ways from participants who drop out • Final sample is not representative of the group (population) researcher wanted to study—findings may not generalize • Practice effects • Change due to familiarity with data collection procedures rather than change due to development

16. Time-consuming and expensive

17. Cross-sectional Designs • Multiple cohorts (and multiple ages) are examined at a single time of assessment • Cohort and age are confounded • Differences across cohorts may produce changes in the dependent variable • Ex: Cohorts born in 1970 and 1990 are likely to differ with respect to early child care experiences • If we see differences in social competence in a cross-sectional design, are they due to age or to cohort differences?

18. Advantages • More efficient than a longitudinal design (faster, less expensive) • No participant loss • No practice effects

19. Disadvantages • Cannot examine stability or change in individual children’s characteristics or behavior over time

20. Complex Developmental Designs (Sequential Designs) • Involve complete crossing of 2 of 3 variables (cohort, age, time of assessment) • Interpretation of data from these designs is still ambiguous • Results cannot be clearly attributed to one of the three variables (confounding is still present)

21. Baltes (1968) argued for the use of the cohort-sequential design in studies of development • Allows for the separation of cohort and age effects • But time of assessment is still confounded with both factors • Baltes argues that time of assessment is unlikely to affect data in developmental studies

22. Cohort-sequential design • Different cohorts compared at the same ages (but at different times of assessment)

23. Allows comparison of children of the same age from different cohorts • Ex: Two groups of 15-year-olds (different cohorts); two groups of 20-year-olds (different cohorts) • If the same-age groups are different from one another with respect to the dependent variable(s), have evidence for cohort effects • If not, can attribute any differences to age rather than to cohort • But both are confounded with time of assessment

24. Data Collection Techniques •  Systematic Observation (2 Types) • Naturalistic Observation • Observe child’s behavior in a natural environment • Exs: playground, school, home

25. Structured Observation: • Design a situation that will elicit relevant behavior(s) • Typically conducted in a laboratory setting (but not always) • Observe different children in the same situation

26. Coding Observational Data • Event sampling: Every occurrence of a behavior(s) during a specified observation period is recorded • Time sampling: The observation period is divided into intervals and the occurrence of a behavior(s) is recorded if it occurs during an interval; the same behavior is not coded twice in the same interval • Likely to under- or over-estimate the frequency of behaviors depending on the base rate of the behavior and the size of the interval

27. Ratings: Likert-type scales are used to rate behavior(s) during a specified observation period • Often used for “molar” behaviors (e.g., maternal sensitivity) • Typically require a higher level of inference on the part of observers

28. General Disadvantages (Observation): • Observer Bias • Observer records/judges behavior inaccurately in order to make it consistent with hypotheses or with other beliefs (unintentional!) • Participant Reactivity • Observer’s presence affects behavior of those being observed

29. Self-report Measures • Clinical Interviews • More “open-ended” questions—response choices are not limited • Participants may be asked different questions (depending on their answers)

30. Structured interviews and questionnaires • More “close-ended” questions—response choices are limited • Ex: yes/no questions, rating scales, multiple choice questions • All participants are asked the same questions

31. Parents, child care providers, and teachers often provide information about infants and younger children • Ex: infant/child temperament; behavior problems; social skills

32. General Disadvantage (self-report or report by others): • Data may be inaccurate due to • Deliberate (or semi-deliberate) deception • Misinterpretations of questions • Lower verbal skills • Memory limitations • Lower observational skills • Less knowledge about relevant behaviors

33. Psychophysiological Methods • Record physiological responses • Exs: heart rate, hormone levels (cortisol), brain wave activity • Infer psychological “states” from these responses (e.g., perceptions, emotions)

34. Advantage: • Can be used with preverbal infants and young children (limited language) Disadvantage: • Changes in physiological responses can be caused by many “irrelevant” factors (e.g., hunger, boredom, movement)