Experimental Method

This section explores the experimental method, as part of research methods in psychology. The experimental method is a fundamental approach in psychology used to establish cause-and-effect relationships between variables. In experiments, researchers manipulate an independent variable (IV) to observe its effect on a dependent variable (DV) while controlling other potential influences. There are several types of experiments, including laboratory experiments, field experiments, natural experiments, and quasi-experiments. Each type has unique strengths and limitations, and they differ in terms of control, environment, and the extent to which variables can be manipulated.

Laboratory Experiments

Laboratory experiments take place in a highly controlled environment, often in a research lab. Researchers manipulate the IV and measure its effect on the DV while controlling for extraneous variables, which allows for greater precision and reliability.

Characteristics

• Conducted in a controlled, artificial environment.
• High level of control over variables.
• Participants are aware that they are in an experiment, although they may not know its purpose.

Strengths

• High Control: Extraneous variables are minimised, making it easier to establish a causal relationship between the IV and DV.
• Reliability: The controlled setting and use of standardised procedures make it easier to replicate the study, enhancing reliability.
• Precision in Measurement: Laboratory equipment and controlled conditions allow for precise and accurate data collection.

Limitations

• Low Ecological Validity: The artificial setting may not reflect real-life situations, which limits generalisability to everyday behaviour.
• Demand Characteristics: Participants may guess the aim of the study and alter their behaviour accordingly, which can affect the results.
• Ethical Concerns: The controlled environment may require deception to prevent participants from changing their behaviour, raising ethical issues.

Example

Milgram’s obedience study (1963) is a well-known laboratory experiment where participants were instructed to administer electric shocks to another person. The highly controlled setting allowed Milgram to investigate obedience, though ethical concerns arose due to deception and participant distress.

Field Experiments

Field experiments are conducted in natural, real-world settings rather than in a laboratory. Researchers still manipulate the IV, but the environment is more natural for participants, who may be unaware they are in a study.

Characteristics

• Conducted in real-world settings, such as schools, workplaces, or public spaces.
• Some control over the IV, but less control over extraneous variables compared to laboratory experiments.
• Participants may not be aware they are part of an experiment, which reduces demand characteristics.

Strengths

• Higher Ecological Validity: Because field experiments occur in natural settings, the findings are more likely to be generalisable to real-world behaviour.
• Reduced Demand Characteristics: If participants are unaware of being observed, they are less likely to alter their behaviour, resulting in more genuine responses.

Limitations

• Less Control: Extraneous variables are harder to control in a natural setting, which can lead to confounding variables and affect the validity of results.
• Ethical Issues: Informed consent and debriefing can be challenging if participants are unaware they are part of a study.
• Replication Difficulties: Due to the natural setting and uncontrollable variables, field experiments can be harder to replicate consistently.

Example

Hofling et al. (1966) conducted a field experiment on obedience in a hospital setting, where nurses were instructed by a “doctor” to administer a potentially harmful dose of medication. The natural setting allowed researchers to observe real-world obedience, though informed consent was an issue.

Natural Experiments

Natural experiments are conducted when the researcher cannot manipulate the IV due to ethical or practical reasons; instead, the IV is naturally occurring. The researcher observes the effect of this naturally occurring variable on the DV without directly intervening.

Characteristics

• The IV occurs naturally, and researchers have no control over it.
• Often used to study events or circumstances that would be unethical or impossible to recreate in a lab (e.g., studying the effects of natural disasters on mental health).
• High in ecological validity as they often study real-world events.

Strengths

• High Ecological Validity: Since natural experiments study real-world events, their findings are often generalisable to similar situations.
• Ethically Feasible: By not manipulating the IV, researchers can study situations that would otherwise be unethical to create, such as trauma from natural disasters.
• Unique Insight: Provides valuable data on situations that cannot be replicated in a lab setting.

Limitations

• Lack of Control: Without control over the IV and extraneous variables, it is more challenging to establish a clear cause-and-effect relationship.
• Replication Issues: Because the IV is naturally occurring, it may be difficult or impossible to replicate the experiment exactly.
• Causal Inference: The inability to control the IV limits the researcher’s ability to make firm causal conclusions.

Example

Charlton et al. (2000) studied the impact of the introduction of television on children’s aggression in St. Helena. The natural introduction of television served as the IV, allowing researchers to observe its impact on behaviour without needing to manipulate the situation.

Quasi-Experiments

Quasi-experiments are similar to true experiments but lack full experimental control because participants cannot be randomly assigned to conditions. Instead, groups are often based on existing characteristics, such as age, gender, or a medical condition.

Characteristics

• IV is based on pre-existing differences between participants (e.g., smokers vs. non-smokers).
• No random allocation to conditions; groups are formed based on natural differences.
• Often conducted in controlled environments to maximise internal validity.

Strengths

• Practicality: Quasi-experiments enable the study of variables that cannot be manipulated for ethical or practical reasons, such as gender or mental health conditions.
• Ecological Validity: By studying naturally occurring groups, quasi-experiments provide insight into real-world differences and behaviours.

Limitations

• Lack of Random Assignment: Without random allocation, there is a risk that pre-existing differences between groups could influence the results, potentially introducing confounding variables.
• Limited Causal Inference: It is challenging to establish cause and effect due to the lack of control over group allocation and potential extraneous variables.
• Ethical Issues in Some Cases: If working with vulnerable groups, researchers must ensure ethical considerations, such as informed consent and protection from harm, are upheld.

Example

Baron-Cohen et al. (1997) used a quasi-experiment to study theory of mind in individuals with autism. The participants with autism could not be randomly assigned to the experimental group, as they already had the condition. This allowed researchers to study the cognitive differences associated with autism, but causal conclusions were limited.

Summary Table

Conclusion

The experimental method in psychology includes various types of experiments, each offering different strengths and limitations. Laboratory experiments provide high levels of control but may lack real-world applicability. Field experiments balance some control with higher ecological validity. Natural and quasi-experiments enable the study of variables that cannot be manipulated but present challenges in establishing causation. Together, these methods allow psychologists to investigate human behaviour across diverse contexts, contributing to a comprehensive understanding of psychological processes.