Omar Bennett
Psychology is a relatively young discipline, emerging in the late 1800s. Experimental psychology is a methodology used throughout all areas of psychology, including developmental, social, and health psychology. An experiment in psychology involves the manipulation of variables to establish cause-and-effect relationships. In other words, an experiment investigates the direct effect of an independent variable (IV) on a dependent variable (DV). For example, researchers might compare academic achievement rates among students born before and after a major policy change that increased funding for education. In this case, the independent variable is the timing of the policy change, and the dependent variable is academic achievement. Researchers can use experiments to study many aspects of psychology, such as sensation, perception, memory, cognition, learning, motivation, emotion, and more.
| Characteristics | Values |
|---|---|
| Definition | The experimental method involves the manipulation of variables to establish cause-and-effect relationships. |
| Key Features | Controlled methods and the random allocation of participants into controlled and experimental groups. |
| Experiment Type | Laboratory experiment, field experiment, natural experiment |
| Participants | Humans and animals |
| Topics | Sensation, perception, memory, cognition, learning, motivation, emotion, developmental processes, social psychology, and the neural substrates of all of these. |
| Advantages | Experiments should be objective. The researcher’s views and opinions should not affect a study’s results, making the data more valid and less biased. |
| Disadvantages | Biases can affect the results, and there is a potential for low reliability. |
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What You'll Learn
Laboratory experiments
The controlled nature of laboratory experiments offers several advantages. Firstly, they allow for high precision in measuring variables, which may be impossible in field experiments. Secondly, laboratory experiments tend to produce reliable results that can be replicated since the standardised procedures and controlled conditions can be reproduced.
However, there are also limitations to laboratory experiments. One significant drawback is the potential for low ecological validity, as the artificial setting may not reflect real-life scenarios. This limitation gives rise to the possibility of demand characteristics, where participants may alter their behaviour based on their interpretation of the experiment's purpose, potentially biasing the results.
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Field experiments
Ethical considerations in field experiments include obtaining informed consent from participants and ensuring that interventions do not cause harm or discomfort to individuals or communities. However, obtaining informed consent can be challenging when participants are unaware they are being studied. Researchers must also consider the potential for deception, as participants may encounter situations typical of everyday life that could inadvertently deceive them. It is important in field experiments to debrief participants and give them the opportunity to withdraw any personal data collected.
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Natural experiments
However, natural experiments also have some disadvantages. For example, researchers cannot randomly allocate participants to experimental groups, as they are already pre-set, making them quasi-experiments. This can lead to sample bias, as other extraneous variables associated with the pre-set groups may confound the results. Ethical issues may also arise, especially when conducting studies after traumatic events, as interviewing or observing participants could cause psychological harm.
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Correlational studies
Psychology, as a science, demands that its knowledge be scientifically obtained, verified, and validated. One way to do this is through experiments, which involve the manipulation of variables to establish cause-and-effect relationships. However, there are ethical limitations to what can be studied through experiments. For instance, it would be unethical to take a random group of healthy children and expose them to abusive or traumatic situations to study the relationship between child abuse and coping abilities later in adulthood.
This is where correlational studies come in. Correlational studies are a type of non-experimental research design that seeks to understand the relationships between two or more variables without the researcher manipulating or controlling any of the variables. Instead, data is gathered through surveys (questionnaires and interviews), archival research (past studies that present the data), and naturalistic observation (observation of phenomena as they naturally happen, without intervening). The data is then statistically analysed to verify the relationship between the variables, with the correlation between the variables shown through a value that goes from -1.00 to +1.00. There are three possible outcomes of a correlational study: a positive correlation, a negative correlation, and no correlation.
For example, in 1990, psychologists Thomas Bouchard, David Lykken, and their associates investigated the influence of genes on psychological attributes such as personality and interests. This was hard research to accept at the time, as psychology was mainly focused on behaviourism and how the environment determines behaviour. Bouchard and Lykken's study brought the nature-versus-nurture debate back into the spotlight, aiming to clarify the roles of genes and the environment in shaping who we are.
Another example of a correlational study is a natural experiment in which researchers compare academic achievement rates among students born before and after a major policy change that increased funding for education. In this case, the independent variable is the timing of the policy change, and the dependent variable is academic achievement. The researchers cannot manipulate the independent variable but can observe its effects on the dependent variable.
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Random allocation of participants
In psychology experiments, random allocation ensures that each participant has an equal chance of being assigned to any group, be it a control group or an experimental group. The control group does not receive the treatment, while the experimental group does. By employing random allocation, researchers can be confident that any differences in outcomes across groups result from manipulating the independent variable rather than inherent disparities among participants.
One common technique for random allocation is the use of random number generators or lottery methods. Each member of the study sample is assigned a unique number, and then a random process determines their group placement. Alternatively, simple manual methods such as flipping a coin or rolling dice can also be used to randomly allocate participants.
Random allocation is particularly important in controlled experiments, where it helps strengthen internal validity and avoid biases. It eliminates the influence of confounding variables by distributing them randomly among the groups. This allows researchers to attribute outcomes solely to the intervention being studied and rule out alternative explanations.
For example, in a weight-loss program study, investigators randomly assigned participants to two groups. Group A participated in the program and took a class on healthy eating and exercise, while Group B only received a book on weight loss. The random allocation ensured that any weight loss differences between the groups could be attributed to the intervention and not pre-existing characteristics of the participants.
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Frequently asked questions
An experiment in psychology is a study that investigates the direct effect of an independent variable (IV) on a dependent variable (DV).
The key features of a psychological experiment are controlled methods and the random allocation of participants into controlled and experimental groups.
Psychological experiments are conducted to establish cause-and-effect relationships and gain insights into human thoughts and behaviours.
Examples of psychological experiments include studying the effects of serotonin levels on prefrontal cortex activity, the impact of testosterone on aggression, and the effects of dividing attention between electronic devices and lectures on learning abilities.
Advantages of psychological experiments include objectivity and validity as the researcher's views should not influence the results. Experiments can also be useful when research funds are limited or time is a factor. However, a disadvantage is the potential for biases to affect the results and the challenge of replicating the study due to low reliability.
