The Scientific Method

Psychology and the Scientific Method: From Theory to Conclusion

The scientific method offers a standardized way for psychologists to test hypotheses, build on theories, and gain knowledge about the mind.

Learning Objectives

Defend each step of the scientific method as necessary to psychological research

Key Takeaways

Key Points

  • The scientific method was first outlined by Sir Francis Bacon (1561-1626) to provide logical, rational problem solving across many scientific fields.
  • The basic steps of the scientific method are: 1) make an observation that describes a problem, 2) create a hypothesis, 3) test the hypothesis, and 4) draw conclusions and refine the hypothesis.
  • The major precepts of the scientific method employed by all scientific disciplines are verifiability, predictability, falsifiability, and fairness.
  • The application of the scientific theory to psychology took the discipline from a form of philosophy to a form of science.
  • Critical thinking is a key component of the scientific method. Without it, you cannot use logic to come to conclusions.

Key Terms

  • social science: Sciences concerned with the social behavior of individuals and groups (e.g., sociology, anthropology, or psychology) and that are often considered more subjective due to the focus of study.
  • scientific method: A method of discovering knowledge about the natural world based on making falsifiable predictions (hypotheses), testing them empirically, and developing peer-reviewed theories that best explain the known data.
  • natural science: Sciences concerned with predicting and describing natural phenomena (e.g., biology, physics, or chemistry), using systematic data collection and performing controlled experiments.

All scientific disciplines are united by their use of the scientific method. The scientific method offers an objective methodology for scientific experimentation that results in unbiased interpretations of the world and refines knowledge. The scientific method was first outlined by Sir Francis Bacon (1561–1626) and allows for logical, rational problem solving across many scientific fields. Across all scientific disciplines, the major precepts of the scientific method are verifiability, predictability, falsifiability, and fairness.


The Scientific Method: The scientific method is a process for gathering data and processing information. It provides well-defined steps to standardize how scientific knowledge is gathered through a logical, rational problem-solving method. This diagram shows the steps of the scientific method, which are listed below.

The Basic Principles of the Scientific Method

Two key concepts  in the scientific approach are theory and hypothesis. A theory is used to make predictions about future observations. A hypothesis is a testable prediction that is arrived at logically from a theory.

Several types of studies exist within the scientific method— experiments, descriptive studies, case studies, surveys, and non-descriptive studies. In an experiment a researcher manipulates certain variables and measures their effect on other variables in a controlled environment. Descriptive studies describe the nature of the relationship between the intended variables, without looking at cause or effect. A case study covers one specific example in which something unusual has occurred. This is often done in extreme or rare cases, usually with a single subject. Surveys are used with large groups of people who answer questions about specific subjects. Non-descriptive studies use correlational methods to predict the relationship between two (or more ) intended variables.

Verifiability means that an experiment must be replicable by another researcher. To achieve verifiability, researchers must make sure to document their methods and clearly explain how their experiment is structured and why it produces certain results.

Predictability in a scientific theory implies that the theory should enable us to make predictions about future events. The precision of these predictions is a measure of the strength of the theory.

Falsifiability refers to whether a hypothesis can disproved. For a hypothesis to be falsifiable, it must be logically possible to make an observation or do a physical experiment that would show that there is no support for the hypothesis. Even when a hypothesis cannot be shown to be false, that does not necessarily mean it is not valid. Future testing may disprove the hypothesis. This does not mean that a hypothesis has to be shown to be false, just that it can be tested.

To determine whether a hypothesis is supported or not supported, psychological researchers must conduct hypothesis testing using statistics. Hypothesis testing is a type of statistics that determines the probability of a hypothesis being true or false. If hypothesis testing reveals that results were “statistically significant,” this means that there was support for the hypothesis and that the researchers can be reasonably confident that their result was not due to random chance. If the results are not statistically significant, this means that the researchers’ hypothesis was not supported.

Fairness implies that all data must be considered when evaluating a hypothesis. A researcher cannot pick and choose what data to keep and what to discard or focus specifically on data that support or do not support a particular hypothesis. All data must be accounted for, even if they invalidate the hypothesis.

The Basic Steps of the Scientific Method

The basic steps in the scientific method are:

  • Observe a natural phenomenon and define a question about it
  • Make a hypothesis, or potential solution to the question
  • Test the hypothesis
  • If the hypothesis is true, find more evidence or find counter-evidence
  • If the hypothesis is false, create a new hypothesis or try again
  • Draw conclusions and repeat–the scientific method is never-ending, and no result is ever considered perfect

In order to ask an important question that may improve our understanding of the world, a researcher must first observe natural phenomena. By making observations, a researcher can define a useful question. After finding a question to answer, the researcher can then make a prediction (a hypothesis) about what he or she thinks the answer will be. This prediction is usually a statement about the relationship between two or more variables. After making a hypothesis, the researcher will then design an experiment to test his or her hypothesis and evaluate the data gathered. These data will either support or refute the hypothesis. Based on the conclusions drawn from the data, the researcher will then find more evidence to support the hypothesis, look for counter-evidence to further strengthen the hypothesis, revise the hypothesis and create a new experiment, or continue to incorporate the information gathered to answer the research question.

Example of the Scientific Method

To better understand the process of the scientific method, take a look at the following example:

  • Observation: My toaster doesn’t work.
  • Question: Is something wrong with my electrical outlet?
  • Hypothesis: If something is wrong with the outlet, my coffeemaker also won’t work when plugged into it.
  • Experiment: I plug my coffeemaker into the outlet.
  • Result: My coffeemaker works!
  • Conclusion: My electrical outlet works, but my toaster still won’t toast my bread.
  • Refine the hypothesis: My toaster is broken.

From this point, the process would be repeated with a refined hypothesis.

Why the Scientific Method Is Important for Psychology

The use of the scientific method is one of the main features that separates modern psychology from earlier philosophical inquiries about the mind. Compared to chemistry, physics, and other “natural sciences,” psychology has long been considered one of the “social sciences” because of the subjective nature of the things it seeks to study. Many of the concepts that psychologists are interested in—such as aspects of the human mind, behavior, and emotions—are subjective and cannot be directly measured. Psychologists often rely instead on behavioral observations and self-reported data, which are considered by some to be illegitimate or lacking in methodological rigor. Applying the scientific method to psychology, therefore, helps to standardize the approach to understanding its very different types of information.

The scientific method allows psychological data to be replicated and confirmed in many instances, under different circumstances, and by a variety of researchers. Through replication of experiments, new generations of psychologists can reduce errors and broaden the applicability of theories. It also allows theories to be tested and validated instead of simply being conjectures that could never be verified or falsified. All of this allows psychologists to gain a stronger understanding of how the human mind works.

Scientific articles published in journals and psychology papers written in the style of the American Psychological Association (i.e., in “APA style”) are structured around the scientific method. These papers include an Introduction, which introduces the background information and outlines the hypotheses; a Methods section, which outlines the specifics of how the experiment was conducted to test the hypothesis; a Results section, which includes the statistics that tested the hypothesis and state whether it was supported or not supported, and a Discussion and Conclusion, which state the implications of finding support for, or no support for, the hypothesis. Writing articles and papers that adhere to the scientific method makes it easy for future researchers to repeat the study and attempt to replicate the results.