Chapter 1 - Introduction & Research Methods What is development?

Specific changes over time Physical features Perception Cognition Language Emotion Social abilities Moral functioning Other talents/abilities, creativity

Integration of specific abilities into whole

Change does not end with childhood Adolescence as end of development vs. lifespan perspective

Why study child development? To gain insight into basic human nature, based on science To gain insight into adult behavior To gain knowledge about developmental abnormalities To learn ways to optimize the developmental conditions for all children

III.Research methods Different methods to answer different questions A.Does one factor cause another? The Scientific Method - obtain reliable information under controlled conditions

Example: Does day care lead to adjustment problems? Day care vs. home care => independent variable (IV) Adjustment problems => dependent variable (DV)

Groups: Experimental vs. Control Experimental = receive treatment being tested Control = comparison

DV depends upon IV How will we know if differences in adjustment are caused by day/home care?

Treatment of children (IV) - that which you are manipulating, systematically altering to see its effects CONFOUND = any other difference between the groups

If no confounds, only thing different between the groups is the IV, then high internal validity Fairly sure that changes in the DV were due to IV

How to increase internal validity? -make groups same except for IV -2 ways

1.How to assign groups? ***Random assignment of subjects to groups (experimental & control) Random assignment makes the 2 groups equivalent at beginning of experiment

2.During experiment: No other differences between groups (“holding everything constant”) These 2 factors decrease confounds, & increase internal validity

Subjects/Who is in the experiment Population = all people of interest Sample = subset; those in the experiment

Sample of convenience Random sampling - everyone in population has an equal chance of being chosen - not part of scientific method

Why random sampling? Sample is representative of the population of interest Can apply (“generalize”) results to population Increases external validity

External validity = generalizability To other people, places, situations, etc.

Key to Scientific Method = internal validity Controls to ensure that IV -> DV Rule out confounds Random sampling is not critical Increases external validity

Problems: Not always feasible or ethical Studies are analogues – simulations of real life (low external validity)

Advantage of Scientific Method Cause and effect

B. How strongly are two factors are related? Correlational designs Examples Longitudinal (change over time) Naturalist observation (in natural settings)

Not a true experiment No controls Is there a numerical relationship between 2+ factors?

Evaluating the outcome A correlation coefficient - indicates whether two variables are related -1.0 to +1.0

Magnitude: absolute value of # = strength of relation Direction: sign + = as one increases, other increases - = as one increases, other decreases

Relationships: Positive Negative None Curvilinear

Problem poor internal validity -> don’t know WHY things happen Reverse causality Third-variable problem Spurious relationships

Advantages easier, practical ethical, real-life -> can have better external validity

C.What can we learn from one subject? Three methods: Case study ABAB (Reversal) design Multiple-baseline design

Case study method - documenting behavior of one person

Advantages: Real life (somewhat higher external validity) Suggests ideas Practical, easy (one person) Lots of information

Disadvantages: No controls/comparison (poor internal validity) One subject not randomly selected (poor external validity)

Two experimental methods for single subjects - more control ABAB (Reversal) Multiple-Baseline

ABAB (Reversal) Get baseline (A) Introduce treatment (B) Return to baseline (A) Reintroduce treatment (B)

Advantages: More controlled than case study Still requires only 1 subject

Disadvantages: One person = limited external validity Sometimes unethical to withdraw treatment If return to baseline, then no cure

Multiple-baseline design = change several behaviors sequentially Get baseline for all behaviors Introduce treatment for first behavior Then, treatment for second, etc. Different treatments affect different behaviors

Advantages: More controlled than case study Also requires only 1 subject No withdrawal of treatment

Disadvantages: One person = limited external validity Sometimes hard to disentangle effects on individual behaviors

How do people develop? - Study change over time, aging Longitudinal Cross-sectional Sequential Usually correlational

Longitudinal one group measured multiple times Advantage actually measures development

Disadvantages Time Expense Attrition (not random) Limited causality Cohort effects

Cross-sectional 2+ age groups measured once Advantage easier, cheaper, faster

Disadvantages Not true development, just age-group differences Cohort effects

Sequential 2+ groups at 2+ times Advantages True development Easier than longitudinal Rule out cohort effects

Disadvantage More difficult than cross-sectional

You think maternal drinking during pregnancy leads to childhood problems (such as lower intelligence and worse school performance). How would you design a study to answer this question? What problems and advantages does your design have?