Clever Grades

🎧 Read Aloud

Experiments in Psychology

The Fundamental Principle

Causation: IV → DV

Experiments are a fundamental research method in psychology designed to investigate cause-and-effect relationships between variables. The key principle is to manipulate an independent variable (IV) and observe changes in a dependent variable (DV) while controlling extraneous variables.

Classification of Experiments

1

Laboratory Experiments

These take place in highly controlled environments, optimizing internal validity.
2

Field Experiments

Conducted in real-world environments with manipulated IVs, maximizing ecological validity.
3

Quasi-Experiments

The IV is based on pre-existing characteristics or conditions (e.g., age, gender).

Essential Variables

Understanding these core variables is crucial for designing and interpreting experimental results.

⚙️

Independent Variable (IV)

The variable manipulated by the researcher to see if it causes an effect.
🎯

Dependent Variable (DV)

The outcome measure that is recorded to assess the effect of the IV.
🚧

Extraneous Variables

Variables other than the IV that could influence the DV and thereby threaten validity.

Controlling Validity Threats

💡

Controlling Extraneous Variables: Researchers use randomization (random allocation of participants to conditions) and standardization (keeping procedures uniform) to reduce the influence of extraneous variables. Control groups and counterbalancing may also be applied.

Lab Experiments: Control vs. Reality

✅
StrengthsHigh control: Environment can be standardized, improving cause-and-effect interpretations (high internal validity). Replicability: Easier to replicate due to standardization.
❌
WeaknessesArtificiality: Controlled setting can be unnatural, causing participants’ behavior to lack ecological validity. Demand characteristics: Participants may guess the experiment’s purpose and alter behavior.

Field Experiments: Reality & Generalizability

✅
StrengthsHigh ecological validity: Behavior is more natural since participants are in a real-life environment, increasing generalizability. Reduced demand characteristics: Participants may be unaware they are part of an experiment.
❌
WeaknessesLess control: Many extraneous variables cannot be controlled, which can threaten internal validity. Ethical issues: Conducting research without informed consent or full awareness can be problematic.

Quasi-Experiments: Natural Differences

✅
StrengthsAllows study of variables that cannot be manipulated: Useful where ethical or practical constraints prevent true experiments. Real-world relevance: Often conducted in natural settings, increasing ecological validity.
❌
WeaknessesCannot establish causality confidently: Confounding variables may influence results because groups are not randomly assigned. Lower internal validity: Cannot conclusively infer cause and effect.

Core Experimental Designs

Researchers choose a design based on controlling participant variability versus managing potential order effects.

✓

Repeated Measures Design

The same participants experience all conditions. Controls participant variables but introduces order effects (practice/fatigue).
✓

Independent Groups Design

Different participants take part in each condition. Reduces order effects but increases participant variability.
✓

Matched Pairs Design

Participants are paired based on key variables, then assigned to different conditions. Time consuming but balances variables.

Summary Comparison Matrix

Review of how different experimental settings balance control, validity, and ethics.

Aspect Strengths Weaknesses Type ... ... ... ...
Control High in lab; allows causation Low in field; quasi less control Lab/Field
Validity Internally valid (lab) Ecologically valid (field) Lab/Field
Replicability High in lab; harder in field Less in field/quasi Lab/Field
Ethics Easier to manage Field and quasi can face ethical issues All
Generalizability Can be limited due to artificiality Better ecological validity in field Lab/Field
Experimentation Terms Deck
Term
Independent Variable (IV)

What is the independent variable (IV) in an experiment?

Answer
Definition

The variable that is manipulated by the researcher to observe its effect.

Term
Laboratory Experiment

What defines a laboratory experiment?

Answer
Definition

Experiments conducted in a controlled environment where extraneous variables are minimized.

Term
Strength of Field Experiments

Name one strength of field experiments.

Answer
Strength

High ecological validity because they occur in real-world settings.

Term
Quasi-Experiment

What is a quasi-experiment?

Answer
Definition

An experiment where the IV is not manipulated but based on natural groups or pre-existing conditions.

Term
Randomization

Why is randomization important in experiments?

Answer
Importance

It reduces the influence of extraneous variables and helps ensure group equivalence.

Term
Weakness of Quasi-Experiments

What is the main weakness of quasi-experiments?

Answer
Weakness

They cannot confidently establish causality due to lack of random assignment and potential confounds.

Term
Order Effect

What is an order effect in repeated measures designs?

Answer
Definition

Changes in performance caused by the order in which conditions are presented, such as practice or fatigue.

Term
Standardization and Control

How do standardization and control improve an experiment?

Answer
Importance

They help reduce extraneous variables and improve internal validity.

Term
Ethical Concern in Field Experiments

What ethical concern is commonly associated with field experiments?

Answer
Concern

Participants may not give informed consent or be fully aware of the study.

Term
Matched Pairs Design

What is a matched pairs design?

Answer
Definition

Participants are paired on key variables and each member is assigned to different experimental conditions.

Tip: Tap a card to flip. Shuffle or Reset anytime.

🧠 Experiments in Psychology Quiz

1. Which of the following is the main advantage of laboratory experiments?

Laboratory experiments give researchers the ability to control extraneous variables, increasing internal validity.

2. What is a potential weakness of field experiments?

Because field experiments occur in natural settings, it is harder to control all external influences, which can threaten internal validity.

3. True or False: Quasi-experiments allow researchers to manipulate the independent variable.

In quasi-experiments, the IV is based on natural groupings and is not manipulated.

4. Which design helps control for participant variables by having the same participants experience all conditions?

Repeated measures designs involve the same participants across all conditions, controlling for individual differences.

5. Which method is used to reduce the impact of extraneous variables?

Random allocation of participants helps evenly distribute potential extraneous variables across conditions.

📊 Results

  • Notes and Quiz
  • Psychology
  • AS Level
  • Research Methods
  • OCR