2 maturation and history

Introduction

  • The lecturer addresses the class, mentioning a personal health issue related to allergies that may affect their voice.

  • Assures students that they are not sick, and humorously reflects on listeners' likely indifference to any voice changes.

Threats to Internal Validity

  • Overview of internal validity concerns in research designs.

  • The lecture focuses on threats 4 (Maturation) and 5 (History).

Maturation Threats

  • Definition of Maturation:

    • Maturation refers to the process of participants getting older over time.

    • Performance changes can occur as a function of participant maturation rather than the independent variable.

    • Example: In repeated measures independent variables, longer intervals between measurements increase the risk of maturation effects.

  • Issues in Longitudinal Research:

    • Maturation effects are especially problematic in longitudinal studies.

    • These studies assess changes over time within the same subject.

Spontaneous Remission

  • Definition of Spontaneous Remission:

    • Occurs when improvement happens without any clear external reason, particularly in clinical and medical research.

  • Example in Animal Research:

    • Laboratory studies on rats, where chemically induced cancer in rats sometimes resolves without treatment.

    • This phenomenon complicates assessments of treatment efficacy.

    • Ethical considerations are mentioned concerning animal rights and the practice of inducing illness for research.

  • Spontaneous remission can also be observed in humans but without controlled experimentation comparable to animals.

Control Groups as a Solution

  • Importance of including a control group:

    • A control group allows for comparison, attributing improvements solely to the treatment rather than maturation.

  • Example of Cancer Study:

    • If 12 rats in an experimental group receive treatment and 12 in a control group do not, improvements in the experimental group can be analyzed.

Application of Maturation in Research

  • Maturation is particularly crucial when studying variables that vary significantly over time, especially those expected to improve with age.

  • Examples of Areas Affected by Maturation:

    • Cognitive Development in Children:

    • Children's intellect naturally improves with age hence requiring control groups when assessing intellectual interventions.

    • Memory Decline:

    • As people age, memory may naturally decline, necessitating control measures in research.

    • Athletic Performance:

    • Athletic abilities follow an inverted U-shape trajectory, improving until a peak age and then declining, which affects research design.

  • Example Scenario: A sports psychologist tests mindfulness training on 50 cross-country runners with one group pretest/posttest design.

    • Initial speed measured in April, followed by weekly mindfulness training for four months, with a follow-up speed measurement in August.

    • No control group introduces maturation threats as the only reason for speed improvement cannot be conclusively determined.

    • Improvements could be due to practice versus the effectiveness of mindfulness training.

Conclusion on Maturation Effects

  • Without a control group, it is difficult to separate maturation effects from treatment effects.

  • Control groups clarify whether improvements are due to independent variable manipulation or general maturation.

History Effects

  • Definition of History Effects:

    • Differentiates the maturation effect, where the cause of change is external events impacting the entire group rather than individual maturation.

  • Example Historical Events:

    • The assassination of President John F. Kennedy significantly impacted the collective consciousness and could influence research results.

    • An increase in sales tax or an unusually hot summer may introduce history effects in consumer behavior studies.

    • Local sports team victories could skew purchase behavior studies.

  • Example of Significant Historical Impact: During a study on a new antidepressant, the September 11 attacks impacted results, confounding the cause of any observed changes in participant mood.

  • Importance of Using Control Groups:

    • In events affecting both control and treatment groups, such as September 11, some results may still be interpretable.

    • However, for major historical events, the robustness of findings can be questioned.