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 lower- quality 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 cross- sectional 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 Time of Assessment

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)