Experimental Research Methods

Experimental Research

• Considered the gold standard for establishing causation and determining validity.
• Involves the manipulation of independent variables, such as different therapies, medications, or exercise levels.
• Relies on random assignment of participants to conditions.
• Aims to establish causal relationships between variables.
• Places a high value on internal validity.

Group Experimental Designs

• Control groups are essential to demonstrate that the independent variable is responsible for observed changes.
• The control group should be as similar as possible to the treatment group.
• Placebo controls are used to ensure treatment effects are not due to expectations of improvement.

Placebo and Double-Blind Controls

• Placebo controls are easier to implement with medications but more challenging with psychological treatments.
• Double-blind designs involve both researchers and participants being unaware of group assignment.

Comparative Treatment Designs

• Aims to compares different forms of treatment for similar individuals.
• Addresses treatment outcome by assessing if change has occurred.
• Dismantling studies break down treatments to identify active components.

Single-Case Experimental Designs

• Involves the systematic study of individuals under varying conditions.
• Employs rigorous study of single cases through manipulation of experimental conditions and time.
• Relies on repeated measurement, unlike larger studies that measure only before and after treatment.
• Aims to ensure internal validity.

Types of Single-Subject Design

• Withdrawal designs involve assessing a baseline, introducing treatment, and then withdrawing treatment to assess changes.
• Assets: better sense if treatment caused changes
• Liabilities: risks of relapse; impossible to “withdraw” most psychological treatments.
• Multiple baseline designs introduce interventions at different times across settings to avoid withdrawing treatment.
• Assets: don’t have to withdrawal treatment
• Liabilities: conclusions are based on a small number of people

Genetic Research Strategies

• Behavioral genetics studies the interaction among genes, experience, and behavior.
• Phenotype refers to observable characteristics, while genotype is an individual's genetic makeup.
• Down syndrome phenotype includes intellectual disability; the genotype involves an extra 21st chromosome.

Strategies Used in Genetic Research

• Family studies examine behavioral patterns/emotional traits in family members.
  • Cannot distinguish between environmental and genetic factors.
• Adoptee studies separate environmental from genetic contributions by comparing children to adoptive and biological parents.
  • Research suggests a heritable component to crime, particularly property crime.
• Twin studies evaluate psychopathology in fraternal vs. identical twins.
• Monozygotic twins schizophrenia risk: 48%.
• Dizygotic twins schizophrenia risk: 17%.
• Results require the "equal environment" assumption is correct, that MZ twins are NOT treated any more similarly than DZ twins.
• Genetic wide association studies locate sites of related genes.

Time-Based Research Strategies

• Cross-sectional designs compare different age groups at one time.
• Participants in each age group belong to cohorts.
• Cohort effect: differences across ages may be due to both age and dissimilar experiences
• Limitations: can tell us that two variables are related but not causal information

Longitudinal Designs

• Follow one group over time to assess changes in individuals, eliminating cohort effects.
• Approach helps understanding causality.
• Problems:
• Takes a long time to do
• Expensive
• Participant attrition may occur.
• Cross-generalization effect: study effects may not generalize to other groups with different experiences.

Studying Behavior Across Cultures

• Cross-cultural studies provide insight into origins and treatment of disorders from diverse perspectives.
• Help in overcoming ethnocentric research biases.
• Substance use predictors in caucasian adolescents may not apply to african american adolescents.

Issues in Cross-Cultural Research

• Clarify how psychopathology manifests in different ethnic groups.
• Northwestern cultures emphasize somatic aspects of depression.
• Different thresholds exist for defining abnormal behavior.
• Treatment is influenced by cultural context.