Experimental Psychology: Core Principles & Methodologies

• Experimental psychology uses scientific methods for the study of behavior and mental processes.
• Empirical research, variable manipulation, and controlled experiments are emphasized.

Core Principles

• Objectivity ensures observations and measurements remain free from personal biases.
• Control minimizes extraneous variables effects to isolate the independent variable's impact.
• Replication ensures studies are repeatable, which verifies findings.
• Systematic Variation involves changing independent variables and observing effects.

Research Methodologies

• Experimental designs involve manipulating independent variables and measuring their effects on dependent variables.
• Descriptive methods observe behavior without manipulating variables.
• Correlational methods examine relationships between variables but do not determine causation.

Experimental Designs

• Independent Groups Design involves random assignment of participants to different experimental conditions.
  • Each group gets a different level of the independent variable.
  • It minimizes order effects.
  • It needs larger sample sizes to ensure group equivalence.
• Repeated Measures Design exposes each participant to all levels of the independent variable.
  • It controls for individual differences.
  • It's susceptible to order effects like practice, fatigue, and carryover.
  • Counterbalancing can mitigate order effects.
• Matched Pairs Design pairs participants based on relevant characteristics, assigning each to a different condition.
  • It balances individual differences between groups.
  • It requires identifying and measuring matching variables.
  • It can be time-consuming and hard to implement.
• A control group serves as a baseline for comparison and does not get experimental manipulation.
• Random assignment means participants have an equal chance of being assigned to any condition.
• Blinding (single or double) minimizes experimenter and participant expectancy effects.

Descriptive Methods

• Naturalistic Observation involves observing behavior in a natural setting.
  • It provides high ecological validity.
  • It has limited control over variables.
  • It is susceptible to observer bias.
• Case Studies are an in-depth analysis of an individual or group.
  • They are useful for studying rare phenomena.
  • They have limited generalizability.
  • There is potential for researcher bias.
• Surveys collect data through questionnaires or interviews.
  • They are efficient for gathering data from large samples.
  • They are susceptible to response bias and sampling errors.
• Archival Research analyzes existing data collected for other reasons.
  • It's nonreactive and cost-effective.
  • It is limited by data quality and availability.

Correlational Methods

• Correlation measures the statistical association between variables.
• Correlation coefficients range from -1 to +1.
• Positive correlation means as one variable increases, the other also increases.
• Negative correlation means as one variable increases, the other decreases.
• Zero correlation means there is no relationship between the variables.
• Correlation does not imply causation.

Variables

• Independent Variable (IV) is manipulated by the experimenter.
• Dependent Variable (DV) is measured by the experimenter.
• Extraneous Variables influence the DV but are not the IV.
• Confounding Variables systematically vary with the IV and are extraneous.
• Control variables are kept constant to prevent them from influencing the DV.

Data Collection Techniques

• Self-Report Measures involve participants providing information through questionnaires or interviews.
  • These are susceptible to social desirability bias.
• Behavioral Measures involve observing and recording the behavior of participants.
  • These can be more objective than self-report measures.
  • They may be influenced by observer presence (reactivity).
• Physiological Measures record physiological responses like heart rate, brain activity, or hormone levels.
  • These can provide objective measures of psychological processes.
  • These require specialized equipment and expertise.
• Implicit measures indirectly assess unreported attitudes or beliefs.

Data Analysis

• Descriptive Statistics summarize and describe data (e.g., mean, standard deviation).
• Inferential Statistics infer about a population based on a sample (e.g., t-tests, ANOVA).
• Statistical Significance is the probability of obtaining the observed results if no real effect exists.
• Effect Size is the magnitude of the IV's effect on the DV.

Validity and Reliability

• Internal Validity means a study demonstrates a true cause-and-effect relationship.
• External Validity is the extent to which findings can be generalized to other populations and settings.
• Construct Validity is the extent to which the measures used accurately represent constructs.
• Statistical Conclusion Validity is the extent to which statistical analysis is accurate and reliable.
• Reliability is the consistency and stability of the measures used.
• Test-retest reliability refers to the consistency of results over time.
• Inter-rater reliability refers to agreement between multiple observers or raters.
• Internal consistency refers to the consistency of items within a measure.

Ethical Considerations

• Informed Consent means participants must be fully informed about the study and their right to withdraw.
• Debriefing means participants are informed about the study and any deception used.
• Confidentiality means protecting the privacy of participant data.
• Minimizing Harm means avoiding physical or psychological harm to participants.
• Institutional Review Boards (IRBs) review research proposals to ensure ethical standards are met.

Common Experimental Psychology Paradigms

• Cognitive Psychology studies mental processes like memory, attention, and problem-solving.
  • Examples include reaction time tasks, memory recall tests, and eye-tracking experiments.
• Perception examines how sensory information is perceived and interpreted.
  • Examples include visual illusions, auditory perception tasks, and psychophysics experiments.
• Learning and Memory investigates how information is acquired, stored, and retrieved.
  • Examples include classical conditioning, operant conditioning, and memory encoding tasks.
• Social Psychology explores how individuals think, feel, and behave in social contexts.
  • Examples include conformity experiments, obedience studies, and attitude measurement.
• Developmental Psychology: Studies changes in behavior and mental processes across the lifespan.
  • Examples: Longitudinal studies, cross-sectional studies, infant habituation paradigms.

Challenges in Experimental Psychology

• Demand Characteristics occur when participants alter their behavior based on what they think the experimenter wants.
• Experimenter Bias means the experimenter's expectations can influence study results.
• Cultural Bias means findings may not generalize across different cultures.
• Ethical dilemmas involve balancing knowledge pursuit with participant rights and well-being.
• It is difficult to study complex real-world phenomena in a controlled lab setting.