Developmental Psychology Research Issues Intractable Variables Difficult or

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

• 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?

• 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

• 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

• 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

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

• 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)

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

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 lowerquality child care (socioeconomic status; high-quality parental care) – These “confounding” variables are likely to be related to school readiness

• 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

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

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

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?

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

• 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

– Time-consuming and expensive

• 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 crosssectional design, are they due to age or to cohort differences?

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

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

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)

• 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

• Cohort-sequential design – Different cohorts compared at the same ages (but at different times of assessment) Cohort 1960 1965 Time of Assessment 1975 1980 1985 15 20

• 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

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

– 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

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

– 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

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

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

– 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

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

• 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

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

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)