Types of Experiment | Psychology for A Level - Year 13 PDF Download

Laboratory Experiments

• A laboratory experiment is a research approach where the researcher maintains significant control over the experimental process. 
• The researcher manages environmental factors, such as noise and temperature (potential extraneous variables), to isolate and measure the impact of the independent variable (IV) on the dependent variable (DV). 
• Lab experiments employ a standardized procedure to ensure consistency and replicability. 
• All variables, except the IV, are kept constant across conditions: 
  • The experiment occurs in the same physical space for each condition.
  • Environmental conditions like lighting, temperature, and noise are held consistent.
  • The researcher interacts with participants uniformly (e.g., maintaining consistent tone, body language, and attire) for each condition.
• By controlling all variables except the IV, the DV can be precisely measured using quantitative data.

Evaluation of Laboratory Experiments

Strengths

• Establishing a cause-and-effect link between the independent variable (IV) and dependent variable (DV) is more straightforward compared to other psychological research methods.
  • This is because of the implementation of controls and the objective approach of the study.
  • As a result, lab experiments exhibit high internal validity.
• Employing a standardized procedure ensures the research can be replicated, enhancing its reliability.

Limitations

• The reliance on artificial tasks in lab experiments results in low ecological validity.
  • When participants undertake tasks in an unfamiliar, controlled environment, their behavior may not mirror real-world responses.
  • This limits the ability to apply findings beyond the laboratory context.
• Demand characteristics can reduce the generalizability of results.
  • Knowing they are part of a study, participants may modify their behavior (e.g., feeling shy, self-conscious, or exerting excessive effort).
  • Such changes decrease the external validity of the research.

Field Experiments

• A field experiment is a research approach conducted in a natural, real-world environment outside of a laboratory.
• Due to the real-world setting, the researcher has reduced control over the experimental process. 

While some environmental control is possible, researchers must recognize that numerous extraneous variables influence field experiments, 

• For Example.
  • Outdoor experiments are affected by weather conditions (e.g., sunny weather may improve participants’ mood, while rain may dampen it).
  • Experiments in crowded settings introduce distractions like other people, noise, traffic, or nearby shops.
• Field experiments differ from naturalistic observations as they involve manipulating an independent variable (IV) and measuring a dependent variable (DV). 
  For Examples,
• A researcher’s confederate pretends to collapse on a subway train, with the IV being whether the individual appears drunk or disabled and the DV being the number of people who offer assistance.
• A “Kindness” program is introduced to half of a primary school’s Year 5 students, 
  • The IV being participation in the program and the DV being their scores on a prosocial behavior questionnaire after one month.

Field experiments primarily gather quantitative data, but they also allow for the collection of qualitative data, 

• For Examples.
  • Interviews with subway passengers who observed the collapse.
  • Teachers’ observations of behavioral changes in students participating in the “Kindness” program over the study’s duration.

• Qualitative data collected can provide insights into the quantitative results and clarify participants’ behaviors.

 Evaluation of Field Experiments

Strengths

• Conducting research in natural environments minimizes artificiality.
  • When participants feel at ease in the setting, their behavior is more likely to mirror their actions outside the study’s context.
  • This results in field experiments having high external validity.
• The relaxed, natural setting of field experiments reduces the likelihood of demand characteristics, enhancing the validity of the results.

Limitations

• Extraneous variables are more likely to impact the study’s outcomes.
  • Researchers are unable to control all extraneous variables due to the inherent constraints of field experiments.
  • This leads to decreased reliability.
• Replicating field experiments is challenging due to their real-world nature.
  • This limits the ability to verify the consistency of results, further reducing reliability.

Natural Experiments

• Natural experiments study naturally occurring phenomena
• For Example,
  • The IV cannot be manipulated by the researcher.
  • Participants cannot be randomly assigned to conditions due to the naturally occurring IV.
  • The research occurs in the participants’ natural environment.
  • The researcher observes, measures, and records responses to these natural phenomena.
• ​Examples of naturally occurring phenomena include:
  • Living in a war zone.
  • Experiencing a specific mental illness.
  • Surviving a plane crash.
• Many naturally occurring phenomena would be unethical for researchers to deliberately impose on participants, so they seek out individuals who have experienced or are currently experiencing the phenomenon.
  • The researcher identifies the DV and designs the study to explore the IV’s effects. 

• Natural experiments often take place in real-world environments

• ​For Example,

  • Examining the impact of surviving a natural disaster like a hurricane on stress levels.
  • Investigating the effects of providing care for an individual with dementia.

• Data collection may involve conducting interviews.

  • Unlike lab, field, or quasi-experiments, natural experiments are distinct in their tendency to gather qualitative data.

 Evaluation of Natural Experiments

Strengths

• Natural experiments enable researchers to explore topics that would be unethical to investigate through traditional lab experiments, such as living with a mental illness or surviving a natural disaster.
• This results in natural experiments having high ethical validity.
• Natural experiments exhibit high ecological validity.
  • Participants provide accounts based on their direct, personal experiences.
  • Researchers do not impose controls on the procedure, enhancing mundane realism.

Limitations

• Establishing causal relationships is challenging due to the presence of multiple uncontrolled variables.
  • The lack of procedural controls is a significant drawback of this research method.
  • Researchers must depend on participants’ self-reported experiences, making it difficult to ascertain the precise impact of the phenomena, which reduces the reliability of natural experiments.
• Natural experiments are susceptible to various biases that can undermine the study’s validity, including:
  • Social desirability bias: Participants may portray themselves or their experiences in a overly positive manner.
  • Confirmation bias: Researchers may seek evidence that supports their preconceived notions brought to the study.
  • Sample bias: The sample is limited to individuals who have experienced the phenomenon, restricting the participant pool.

Quasi-Experiments

A quasi-experiment is a research method that uses naturally occurring phenomena as the IV, similar to natural experiments, and does not involve manipulating the IV. 
For Example,

• ​Age: Comparing digit-span recall between younger and older participants.
• Gender: Comparing emotional intelligence task performance between girls and boys.
• Experience: Comparing emotion-recognition task performance between teachers trained in empathy and those untrained.

• Researchers have limited control over the experimental process because they cannot randomly assign participants to conditions.

• The participants themselves represent the conditions of the independent variable (IV), such as young

  • old, female/male, or trained/untrained.

• Quasi-experiments gather quantitative data, as they can be conducted similarly to traditional lab experiments.

• The only variable beyond the researcher’s control is the IV.

Evaluation of Quasi-Experiments

Strengths

• The absence of independent variable (IV) manipulation leads to greater external validity in the findings.

  • Assessing memory test performance between younger and older individuals provides understanding of how age affects recall.

  • Evaluating emotion recognition skills based on empathy training offers insights into its potential benefits for other groups or professions.

• Quasi-experiments adhere to a true experimental structure, allowing replication with participants who share the same demographic characteristics as the original sample
  For Example,

  • The impact of age on recall can be studied repeatedly using the same procedure.

Limitations

• The inability to randomly assign participants to conditions introduces participant variables, complicating the establishment of causality.

  • A study examining age and recall might include participants in either the younger or older group who possess atypically strong memory skills compared to their population, reducing the reliability of quasi-experiments compared to true experiments.

• Quasi-experiments suffer from lower internal validity, as alternative factors may account for the results.

  • Teachers trained in empathy might work in a school that prioritizes emotional intelligence, giving them an inherent advantage in emotion-recognition tasks