PSYC311+2025+Week+2+Lecture_Strathfield

Causality

Importance of Distinguishing Designs

• Address the ability to infer causation in psychological studies.

• Psychology aims to:

  • Describe phenomena (What?)

  • Explain phenomena (Why, How?)

  • Predict phenomena (When?)

  • The articulation of theories in causal terms enhances understanding.

Choosing Research Methods

• Guidance from research questions:

  • Favor experimental designs if possible.

  • Correlational studies used for:

    • Establishing relationships

    • Identifying parameters/ranges

    • Overcoming ethical/practical issues

Causality in Practice

Correlational Examples

• Study Time and Exam Results: Investigates the relationship without asserting direct causation.

• Childhood Neglect and Adult Relationships: Explores potential long-term effects without proving causality.

• Nutrition During Pregnancy: Examines its impact on children's cognitive abilities at age 10 as a correlational study.

Experimental Research Objectives

• Determine the nature of relationships:

  • Assess relationships’ direction and causal assertions.

  • The fundamental goal is establishing causability.

Evaluating Research Quality

Key Criteria

• When conducting research, prioritize:

  • Reliability: Accurate measurement

  • Validity: Measuring what was intended.

Validity Defined

• Quality of being logically or factually sound.

• Distinction between validity and truth:

  • Example: Valid conclusions do not necessarily imply truth.

Types of Validity

1. Construct Validity: Quality of measurement tools.

2. Internal Validity: Assesses the causal relationship between IV and DV.

3. External Validity: Quality of generalization from the research findings to other contexts.

Internal Validity Threats

Definition and Importance

• Evaluating if causality conclusions follow from observations:

  • Need to ensure changes in IV are linked only to observed changes in DV.

Examples of Threats

1. History: External events affecting results (e.g., significant news events between measurements).

2. Maturation: Natural changes affecting participants over time.

3. Testing: Previous tests affecting scores on subsequent tests (practice effects).

4. Instrumentation: Changes or inconsistencies in measurement tools affecting results.

5. Statistical Regression: Participants' scores regress to the mean over repeated measures.

6. Selection: Pre-existing differences between groups impacting results.

7. Mortality: Differences due to dropout rates between groups.

8. Interaction Effects: Effects produced by interactions of selection and other threats.

9. Diffusion or Imitation of Treatment: Cross-contamination between experimental and control groups.

External Validity Threats

Definition and Explanations

• Evaluates the generalization of findings beyond the study context.

Types of External Validity Threats

1. Environmental Validity: Results applicability across different settings.

2. Population Validity: Generalizability to various populations (differences in demographics/characteristics).

3. Temporal Validity: Application of findings across different times or contexts.

Methods and Participant Threats

• Interaction testing-treatment: Findings specific to experimental conditions; issues with pre-testing.

• Interaction selection-treatment: Findings only relevant to selected participant groups.

• Reactive Arrangements: Behaviour change due to participants' awareness of being observed.

• Demand Characteristics: Participants' potential bias by anticipating study expectations.

• Multiple Treatment Interference: Findings possibly influenced by the testing order/multiple assessments.

Conclusion on Validity in Research

• Acknowledgment that all research has limitations and understanding replication and extension can enhance external validity.

• The necessity of thorough evaluation for both internal and external validity enhances the quality of psychological research.