Developmental Psychology

Developmental Psychology Lab 1: Research Methods and Designs

Research Strategy 1) Select research method (Observation, Experiment, Interview, etc.) 2) Decide on research design (Overall plan that permits the best test of research idea) 3) Evaluate procedure for any possible harm to participants

Widely Used Methods 1) Naturalistic Observation 2) Experiment 3) Correlation 4) Interview

1) Naturalistic Observation • In the “field”, or natural environment, where behavior happens • e.g. Observation in a daycare of children’s responses to peer’s distress • Advantage: • Direct observation of everyday behavior • Disadvantage: • Not all children have the same opportunity to display a particular behavior in everyday life

Limitations of Observation • Observer Influence • Participants may react in unnatural ways • Can be minimized • Observer Bias • Observers record what they expect, rather than what really happens • Observed Behavior • Conveys little about the reasoning that underlies the observed behavior

2) Experiment • Researchers assign participants to two or more treatment conditions • Events and behaviors are divided into independent and dependent variables • Advantage: • Permits inferences about cause and effect

Experiment Variables Independent Dependent Experimenter measures, but does not manipulate this variable Expected to be influenced by the independent variable • Experimenter changes, or manipulates this variable • Expected to cause change in another variable

Analyzing Group Differences • Over the course of this semester we will look at various experiments that examine group differences • We will look at differences in group means, and test whether this difference is “significant”, meaning likely to reoccur in further testing (i.e. is it a “real” difference, or a “fluke”) • A common statistical tool to do this, which we will use in several labs, is a “t-test” • Note: These slides provide a brief intro to t-tests, but this will be explained again when we work with them in future labs

t-tests • Two types: • Dependent: • Comparing the same people twice (“before and after”) • e.g. did students’ test scores improve after attending a study group? • Independent: • Comparing 2 different sets of people • e.g. did students in a study group score differently than students who were not in a study group?

t-tests • In order to claim that there is a difference between 2 groups/conditions, we must find a “significant” difference • “Significance” • Does not necessarily mean there is a very large difference • Means that there is over a 95% chance that we would see this difference again if we retested this hypothesis • i.e. There is a less than 5% probability that this difference is a fluke • You will see this written as p <0.05

Modified Experiments Field Experiment Natural Experiment “Quasi-Experiment” Compare differences in groups that already exist Conditions that cannot be experimentally manipulated for ethical reasons (e.g. child maltreatment, premature birth) Groups chosen to match characteristics as much as possible • Use rare opportunities for random assignment in natural settings

3) Correlation • Researchersgather information on individuals, generally in natural life circumstances, and make no effort to alter their experiences • Then they look at relationships between factors, such as links between personal characteristics and developmental outcomes • Advantage: • Able to examine relationships between variables • Disadvantage: • Cannot makes conclusions/inferences about cause and effect (**Important to Note**)

Interpreting Correlations • Correlation Coefficients: • Correlations are described using a number (coefficient) that is either positive or negative, and between 0 and 1 • Magnitude: The size of the number (0-1) • Closer to one indicates a stronger relationship • Direction: Whether it’s positive (+) or negative (-) • Positive (+): As one variable increases, so does the other • Negative (-): As one variable increases, the other decreases

Correlations

4) Interviews • Self-reports ask research participants to provide information on their perceptions, thoughts, abilities, feelings, attitudes, beliefs, and past experiences • Clinical: • Flexible, conversational style • Probes for participant’s point of view • Structured: • Each participant is asked same questions in same way • May use questionnaires, get answers from groups

Limitations of Clinical Interviews • Accuracy of participants’ expectations • Wish to please the interviewer • Trouble recalling exactly • Difficulty articulating answers • Distortions in participants’ • Recall • Judgment 3) Flexibility may make responses too varied

Designs for Studying Development • Looking for information about the way participants change over time • Extend correlational and experimental approaches to include measurements at different ages • These include: 1) Longitudinal designs 2) Cross-sectional designs 3) Sequential designs 4) Micro-genetic designs

Designs for Studying Development

1) Longitudinal • Advantage: • Permits study of common patterns and individual differences in development and relationships between early and later events and behaviors

Longitudinal • Disadvantages: • Biased Sampling The failure to enlist participants who represent the population of interest • Selective Attrition Participants may drop out for other reasons; the ones who remain are likely to differ in important ways from the ones who do not continue …continued…

Longitudinal 3) Practice Effects Performance may improve as a result of repeated testing; better testing skills, increased familiarity with the test (no development factors) 4) Cohort Effects Children developing in the same time period who are influenced by particular cultural and historical conditions; Results based on one cohort may not apply to children developing at other times

2) Cross-Sectional Advantages Disadvantages Does not permit study of individual Age difference may be distorted because of cohort effects • Efficient • Not plagued by selective attrition, practice effects, or theoretical and methodological changes in the field

3) Sequential Advantages Disadvantages May have the same problems as the longitudinal and cross-sectional strategies, but the design itself helps identify difficulties • When the design includes longitudinal sequences, permits both longitudinal and cross-sectional comparisons • Reveals cohort effects • Permits tracking of age-related changes more effectively than the longitudinal design

4) Microgenetic • Longitudinal designs can describe changes over years, but cannot capture the processes that produce these changes • Microgenetic designs: • Are an adaptation of the longitudinal approach • Present children with a novel task and follow their mastery over a series of closely spaced sessions • Within this “microcosm” of development, researchers observe how change occurs • Especially useful for cognitive development (strategies children use to acquire new knowledge)

Considerations • Reliability and Validity • After choosing research methods, it has to be ensured that the procedures provide trustworthy information • Ethical Treatment of Children in Research

Reliability and Validity Reliability Validity How accurately the measure captures the characteristics the researcher is trying to study Internal Validity: Study conditions External Validity: Generalizability • Consistency, repeatability of a measure • Inter-Rater: • Different observers have to agree on what they see • Test-Retest: • Same measurement onseparate occasions

Ethical Treatment of Children in Research • Protection from Harm • Children have the right to be protected from physical and/or psychological harm • Informed Consent • Have the right to have explained to them all aspects of the research that may affect their willingness to participate • Privacy • Right to delete their identity on all information collected • Knowledge of Result • Right to be informed of the results of the research 5) Beneficial Treatments • Children in control groups have the right to alternative beneficial treatments if they are available

Developmental Psychology