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Theory vs Hypothesis in Psychology: Key Differences and Applications

From Freud’s psychoanalytic theory to Pavlov’s classical conditioning, the field of psychology has long grappled with the complex interplay between overarching explanations and testable predictions. This intricate dance between theory and hypothesis forms the backbone of psychological research, shaping our understanding of the human mind and behavior. But what exactly distinguishes a theory from a hypothesis, and why does this distinction matter?

Let’s dive into the fascinating world of psychological research, where grand ideas meet rigorous testing, and where the boundaries between imagination and empirical evidence are constantly being redrawn. As we embark on this journey, we’ll explore the nuances of theories and hypotheses, their roles in advancing our understanding of the human psyche, and how they work together to push the boundaries of psychological knowledge.

The Building Blocks of Psychological Research: Theories and Hypotheses

At the heart of psychological research lie two fundamental concepts: theories and hypotheses. These building blocks form the foundation upon which our understanding of human behavior, cognition, and emotion is constructed. But before we delve deeper into their differences and applications, let’s take a moment to appreciate the historical context that has shaped their development.

The field of psychology has come a long way since its inception in the late 19th century. From the early days of introspection and psychoanalysis to the rise of behaviorism and cognitive psychology, the discipline has witnessed a constant evolution in its approach to understanding the human mind. This journey has been marked by the formulation of numerous theories and the testing of countless hypotheses, each contributing to the rich tapestry of psychological knowledge we have today.

Consider, for instance, the Theory of Mind in psychology . This concept, which explores our ability to attribute mental states to ourselves and others, has spawned numerous hypotheses and research studies. It’s a prime example of how a broad theoretical framework can give rise to specific, testable predictions about human behavior.

The importance of distinguishing between theories and hypotheses cannot be overstated. While they are closely related and often work in tandem, understanding their unique roles and characteristics is crucial for conducting rigorous psychological research. This distinction impacts everything from study design and data interpretation to the application of psychological principles in real-world settings.

Unraveling the Mystery of Psychological Theories

So, what exactly is a psychological theory? At its core, a theory is a comprehensive explanation of a particular phenomenon or set of phenomena. It’s like a grand narrative that attempts to make sense of a wide range of observations and findings within a specific domain of psychology.

Theories in psychology are characterized by several key features. First, they are broad in scope, aiming to explain a wide range of phenomena rather than a single observation. Second, they are based on a substantial body of empirical evidence, often accumulated over years or even decades of research. Third, they provide a framework for generating new hypotheses and predictions, serving as a springboard for further investigation.

Take, for example, the Activity Theory in psychology . This comprehensive framework seeks to understand human behavior in the context of goal-directed activities and social interactions. It’s a perfect illustration of how a psychological theory can provide a lens through which to view and interpret a wide range of human experiences and behaviors.

The purpose of theories in psychological research is multifaceted. They help organize existing knowledge, provide explanations for observed phenomena, generate new research questions, and guide the development of interventions and treatments. In essence, theories serve as the roadmap for psychological inquiry, pointing researchers in promising directions and helping them make sense of their findings.

But theories don’t emerge from thin air. They are built on a foundation of empirical evidence, often starting as smaller, more focused hypotheses that are gradually expanded and refined over time. This iterative process of theory development is what keeps psychology dynamic and ever-evolving.

Demystifying Hypotheses in Psychological Research

While theories provide the big picture, hypotheses zoom in on specific, testable predictions. A hypothesis in psychology is a precise, tentative statement about the relationship between variables or the outcome of a particular manipulation. It’s the bread and butter of empirical research, allowing scientists to put their ideas to the test in a controlled, systematic manner.

There are several types of hypotheses that psychologists work with. The null hypothesis assumes no relationship between variables or no effect of a manipulation. The alternative hypothesis, on the other hand, proposes a specific relationship or effect. Research hypotheses are more general statements of expected outcomes, often derived from existing theories or previous research findings.

Formulating testable hypotheses is a crucial skill for any psychologist. It requires a deep understanding of the subject matter, a keen eye for potential relationships between variables, and the ability to operationalize abstract concepts into measurable terms. This process of hypothetical thought in psychology is what bridges the gap between abstract theories and concrete, empirical research.

Consider the matching hypothesis in psychology , which proposes that individuals are more likely to form and succeed in romantic relationships with partners who are similar in physical attractiveness. This specific, testable prediction exemplifies how hypotheses can be derived from broader theories about attraction and relationship formation.

Drawing the Line: Key Differences Between Theories and Hypotheses

Now that we’ve explored theories and hypotheses individually, let’s highlight the key differences between these two fundamental concepts in psychology.

Scope and breadth are perhaps the most obvious distinctions. Theories are broad, overarching explanations that encompass multiple phenomena and relationships. Hypotheses, in contrast, are narrow, focused predictions about specific relationships or outcomes. It’s like comparing a map of the entire world to a detailed street plan of a single neighborhood.

The level of empirical support required also differs significantly. Theories are built on a substantial body of evidence accumulated over time, often incorporating findings from numerous studies and even multiple disciplines. Hypotheses, on the other hand, can be formulated based on limited evidence or even educated guesses, with the understanding that they will be rigorously tested.

Predictive power and explanatory capacity represent another crucial difference. While theories aim to explain why certain phenomena occur and how different factors interact, hypotheses focus on predicting specific outcomes under particular conditions. Theories provide the “why” and “how,” while hypotheses deal with the “what” and “when.”

Flexibility and adaptability to new evidence also set theories and hypotheses apart. Theories are generally more resilient, capable of incorporating new findings and adjusting to accommodate unexpected results. Hypotheses, being more specific, are often either supported or refuted by individual studies, leading to their acceptance, rejection, or refinement.

The Dynamic Duo: How Theories and Hypotheses Work Together

Despite their differences, theories and hypotheses are not isolated entities in psychological research. They form a dynamic, symbiotic relationship that drives the advancement of psychological knowledge.

Theories inform hypothesis development by providing a conceptual framework from which specific predictions can be derived. They offer researchers a starting point, suggesting potential relationships and outcomes worth investigating. For instance, the broad theoretical framework of cognitive psychology has given rise to numerous specific hypotheses about memory, attention, and problem-solving processes.

Conversely, hypotheses play a crucial role in testing and refining theories. Through the process of trial and error in psychology , researchers use hypotheses to put theories to the test, gathering evidence that either supports, refutes, or necessitates modifications to existing theoretical frameworks.

This iterative process of theory building and hypothesis testing is what keeps psychology vibrant and progressive. It’s a constant cycle of proposing ideas, testing them empirically, and using the results to refine our understanding of human behavior and mental processes.

Consider the evolution of theories about intelligence. From early unidimensional concepts to modern multifaceted models like Howard Gardner’s theory of multiple intelligences, our understanding has been shaped by countless hypotheses and studies. Each new finding has contributed to a more nuanced and comprehensive theoretical framework.

From Theory to Practice: Applying Theories and Hypotheses in Psychology

The interplay between theories and hypotheses isn’t just an academic exercise – it has profound implications for the practice of psychology in various domains.

In research design, theories provide the conceptual foundation upon which studies are built. They guide researchers in choosing relevant variables, formulating appropriate hypotheses, and selecting suitable methodologies. For example, a researcher studying workplace motivation might draw on Theory X and Theory Y in psychology to inform their hypotheses about management styles and employee performance.

When it comes to interpreting results, the relationship between theories and hypotheses becomes even more crucial. Hypothesis testing provides concrete data, but it’s the broader theoretical framework that helps researchers make sense of these findings in a larger context. This interplay is essential for advancing our understanding and avoiding the pitfalls of isolated, disconnected research findings.

In clinical psychology, theories and hypotheses play a vital role in developing and refining therapeutic approaches. Cognitive-behavioral therapy, for instance, is grounded in theories about the relationship between thoughts, emotions, and behaviors. Specific therapeutic techniques are often based on hypotheses derived from these theories, which are then tested and refined through clinical practice and research.

The importance of theories and hypotheses extends to evidence-based practice across various fields of psychology. By providing a solid foundation of empirical support and theoretical understanding, they help practitioners make informed decisions about assessment, intervention, and treatment strategies.

Wrapping Up: The Inseparable Duo of Psychological Research

As we’ve journeyed through the landscape of psychological research, we’ve seen how theories and hypotheses, despite their differences, form an inseparable duo in advancing our understanding of the human mind and behavior.

Theories provide the big picture, offering comprehensive explanations that help us make sense of complex psychological phenomena. They serve as the scaffolding upon which we build our knowledge, guiding research and providing context for our findings.

Hypotheses, on the other hand, are the workhorses of psychological research. They allow us to test specific predictions, gather empirical evidence, and gradually refine our theoretical understanding. Through the process of hypothetical thinking in psychology , researchers bridge the gap between abstract ideas and concrete, testable predictions.

The future of psychology lies in continuing to refine this delicate balance between theory and hypothesis. As new research methods emerge and our understanding of the brain and behavior deepens, we can expect theories to become more nuanced and hypotheses more precise. The rise of interdisciplinary approaches, such as the integration of neuroscience and psychology, promises to open up new avenues for theory development and hypothesis testing.

For students and practitioners alike, understanding the distinction between theories and hypotheses is crucial. It forms the foundation of critical thinking in psychology, enabling us to evaluate research findings, design effective studies, and apply psychological principles in real-world settings.

As we continue to unravel the mysteries of the human mind, let’s remember that every grand theory started as a humble hypothesis, and every well-crafted hypothesis contributes to the broader tapestry of psychological theory. It’s this dynamic interplay that keeps psychology vibrant, relevant, and ever-evolving.

So, the next time you encounter a psychological theory or hypothesis, take a moment to appreciate the intricate dance between these two fundamental concepts. They are, after all, the twin engines driving the fascinating journey of discovery in the world of psychology.

References:

1. Kuhn, T. S. (1962). The Structure of Scientific Revolutions. University of Chicago Press.

2. Popper, K. (1959). The Logic of Scientific Discovery. Routledge.

3. Bem, D. J., & de Jong, H. L. (2006). Theoretical Issues in Psychology: An Introduction. SAGE Publications.

4. Cozby, P. C., & Bates, S. C. (2017). Methods in Behavioral Research (13th ed.). McGraw-Hill Education.

5. Kazdin, A. E. (2017). Research Design in Clinical Psychology (5th ed.). Pearson.

6. Stanovich, K. E. (2013). How to Think Straight About Psychology (10th ed.). Pearson.

7. Lewin, K. (1951). Field Theory in Social Science: Selected Theoretical Papers. Harper & Brothers.

8. Neisser, U. (1967). Cognitive Psychology. Appleton-Century-Crofts.

9. Bandura, A. (1986). Social Foundations of Thought and Action: A Social Cognitive Theory. Prentice-Hall.

10. Glaser, B. G., & Strauss, A. L. (1967). The Discovery of Grounded Theory: Strategies for Qualitative Research . Aldine Publishing Company.

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This is the Difference Between a Hypothesis and a Theory

What to Know A hypothesis is an assumption made before any research has been done. It is formed so that it can be tested to see if it might be true. A theory is a principle formed to explain the things already shown in data. Because of the rigors of experiment and control, it is much more likely that a theory will be true than a hypothesis.

As anyone who has worked in a laboratory or out in the field can tell you, science is about process: that of observing, making inferences about those observations, and then performing tests to see if the truth value of those inferences holds up. The scientific method is designed to be a rigorous procedure for acquiring knowledge about the world around us.

In scientific reasoning, a hypothesis is constructed before any applicable research has been done. A theory, on the other hand, is supported by evidence: it's a principle formed as an attempt to explain things that have already been substantiated by data.

Toward that end, science employs a particular vocabulary for describing how ideas are proposed, tested, and supported or disproven. And that's where we see the difference between a hypothesis and a theory .

A hypothesis is an assumption, something proposed for the sake of argument so that it can be tested to see if it might be true.

In the scientific method, the hypothesis is constructed before any applicable research has been done, apart from a basic background review. You ask a question, read up on what has been studied before, and then form a hypothesis.

What is a Hypothesis?

A hypothesis is usually tentative, an assumption or suggestion made strictly for the objective of being tested.

When a character which has been lost in a breed, reappears after a great number of generations, the most probable hypothesis is, not that the offspring suddenly takes after an ancestor some hundred generations distant, but that in each successive generation there has been a tendency to reproduce the character in question, which at last, under unknown favourable conditions, gains an ascendancy. Charles Darwin, On the Origin of Species , 1859 According to one widely reported hypothesis , cell-phone transmissions were disrupting the bees' navigational abilities. (Few experts took the cell-phone conjecture seriously; as one scientist said to me, "If that were the case, Dave Hackenberg's hives would have been dead a long time ago.") Elizabeth Kolbert, The New Yorker , 6 Aug. 2007

What is a Theory?

A theory , in contrast, is a principle that has been formed as an attempt to explain things that have already been substantiated by data. It is used in the names of a number of principles accepted in the scientific community, such as the Big Bang Theory . Because of the rigors of experimentation and control, its likelihood as truth is much higher than that of a hypothesis.

It is evident, on our theory , that coasts merely fringed by reefs cannot have subsided to any perceptible amount; and therefore they must, since the growth of their corals, either have remained stationary or have been upheaved. Now, it is remarkable how generally it can be shown, by the presence of upraised organic remains, that the fringed islands have been elevated: and so far, this is indirect evidence in favour of our theory . Charles Darwin, The Voyage of the Beagle , 1839 An example of a fundamental principle in physics, first proposed by Galileo in 1632 and extended by Einstein in 1905, is the following: All observers traveling at constant velocity relative to one another, should witness identical laws of nature. From this principle, Einstein derived his theory of special relativity. Alan Lightman, Harper's , December 2011

Non-Scientific Use

In non-scientific use, however, hypothesis and theory are often used interchangeably to mean simply an idea, speculation, or hunch (though theory is more common in this regard):

The theory of the teacher with all these immigrant kids was that if you spoke English loudly enough they would eventually understand. E. L. Doctorow, Loon Lake , 1979 Chicago is famous for asking questions for which there can be no boilerplate answers. Example: given the probability that the federal tax code, nondairy creamer, Dennis Rodman and the art of mime all came from outer space, name something else that has extraterrestrial origins and defend your hypothesis . John McCormick, Newsweek , 5 Apr. 1999 In his mind's eye, Miller saw his case suddenly taking form: Richard Bailey had Helen Brach killed because she was threatening to sue him over the horses she had purchased. It was, he realized, only a theory , but it was one he felt certain he could, in time, prove. Full of urgency, a man with a mission now that he had a hypothesis to guide him, he issued new orders to his troops: Find out everything you can about Richard Bailey and his crowd. Howard Blum, Vanity Fair , January 1995

And sometimes one term is used as a genus, or a means for defining the other:

Laplace's popular version of his astronomy, the Système du monde , was famous for introducing what came to be known as the nebular hypothesis , the theory that the solar system was formed by the condensation, through gradual cooling, of the gaseous atmosphere (the nebulae) surrounding the sun. Louis Menand, The Metaphysical Club , 2001 Researchers use this information to support the gateway drug theory — the hypothesis that using one intoxicating substance leads to future use of another. Jordy Byrd, The Pacific Northwest Inlander , 6 May 2015 Fox, the business and economics columnist for Time magazine, tells the story of the professors who enabled those abuses under the banner of the financial theory known as the efficient market hypothesis . Paul Krugman, The New York Times Book Review , 9 Aug. 2009

Incorrect Interpretations of "Theory"

Since this casual use does away with the distinctions upheld by the scientific community, hypothesis and theory are prone to being wrongly interpreted even when they are encountered in scientific contexts—or at least, contexts that allude to scientific study without making the critical distinction that scientists employ when weighing hypotheses and theories.

The most common occurrence is when theory is interpreted—and sometimes even gleefully seized upon—to mean something having less truth value than other scientific principles. (The word law applies to principles so firmly established that they are almost never questioned, such as the law of gravity.)

This mistake is one of projection: since we use theory in general use to mean something lightly speculated, then it's implied that scientists must be talking about the same level of uncertainty when they use theory to refer to their well-tested and reasoned principles.

The distinction has come to the forefront particularly on occasions when the content of science curricula in schools has been challenged—notably, when a school board in Georgia put stickers on textbooks stating that evolution was "a theory, not a fact, regarding the origin of living things." As Kenneth R. Miller, a cell biologist at Brown University, has said , a theory "doesn’t mean a hunch or a guess. A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”

While theories are never completely infallible, they form the basis of scientific reasoning because, as Miller said "to the best of our ability, we’ve tested them, and they’ve held up."

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Hypothesis vs. Theory

A hypothesis is either a suggested explanation for an observable phenomenon, or a reasoned prediction of a possible causal correlation among multiple phenomena. In science , a theory is a tested, well-substantiated, unifying explanation for a set of verified, proven factors. A theory is always backed by evidence; a hypothesis is only a suggested possible outcome, and is testable and falsifiable.

Comparison chart

Examples of theory and hypothesis.

Theory: Einstein's theory of relativity is a theory because it has been tested and verified innumerable times, with results consistently verifying Einstein's conclusion. However, simply because Einstein's conclusion has become a theory does not mean testing of this theory has stopped; all science is ongoing. See also the Big Bang theory , germ theory , and climate change .

Hypothesis: One might think that a prisoner who learns a work skill while in prison will be less likely to commit a crime when released. This is a hypothesis, an "educated guess." The scientific method can be used to test this hypothesis, to either prove it is false or prove that it warrants further study. (Note: Simply because a hypothesis is not found to be false does not mean it is true all or even most of the time. If it is consistently true after considerable time and research, it may be on its way to becoming a theory.)

This video further explains the difference between a theory and a hypothesis:

Common Misconception

People often tend to say "theory" when what they're actually talking about is a hypothesis. For instance, "Migraines are caused by drinking coffee after 2 p.m. — well, it's just a theory, not a rule."

This is actually a logically reasoned proposal based on an observation — say 2 instances of drinking coffee after 2 p.m. caused a migraine — but even if this were true, the migraine could have actually been caused by some other factors.

Because this observation is merely a reasoned possibility, it is testable and can be falsified — which makes it a hypothesis, not a theory.

• What is a Scientific Hypothesis? - LiveScience
• Wikipedia:Scientific theory

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Comments: Hypothesis vs Theory

Anonymous comments (2).

October 11, 2013, 1:11pm "In science, a theory is a well-substantiated, unifying explanation for a set of verified, proven hypotheses." But there's no such thing as "proven hypotheses". Hypotheses can be tested/falsified, they can't be "proven". That's just not how science works. Logical deductions based on axioms can be proven, but not scientific hypotheses. On top of that I find it somewhat strange to claim that a theory doesn't have to be testable, if it's built up from hypotheses, which DO have to be testable... — 80.✗.✗.139

May 6, 2014, 11:45pm "Evolution is a theory, not a fact, regarding the origin of living things." this statement is poorly formed because it implies that a thing is a theory until it gets proven and then it is somehow promoted to fact. this is just a misunderstanding of what the words mean, and of how science progresses generally. to say that a theory is inherently dubious because "it isn't a fact" is pretty much a meaningless statement. no expression which qualified as a mere fact could do a very good job of explaining the complicated process by which species have arisen on Earth over the last billion years. in fact, if you claimed that you could come up with such a single fact, now THAT would be dubious! everything we observe in nature supports the theory of evolution, and nothing we observe contradicts it. when you can say this about a theory, it's a pretty fair bet that the theory is correct. — 71.✗.✗.151

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Introduction to Research Methods in Psychology

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Emily is a board-certified science editor who has worked with top digital publishing brands like Voices for Biodiversity, Study.com, GoodTherapy, Vox, and Verywell.

There are several different research methods in psychology , each of which can help researchers learn more about the way people think, feel, and behave. If you're a psychology student or just want to know the types of research in psychology, here are the main ones as well as how they work.

Three Main Types of Research in Psychology

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Psychology research can usually be classified as one of three major types.

1. Causal or Experimental Research

When most people think of scientific experimentation, research on cause and effect is most often brought to mind. Experiments on causal relationships investigate the effect of one or more variables on one or more outcome variables. This type of research also determines if one variable causes another variable to occur or change.

An example of this type of research in psychology would be changing the length of a specific mental health treatment and measuring the effect on study participants.

2. Descriptive Research

Descriptive research seeks to depict what already exists in a group or population. Three types of psychology research utilizing this method are:

• Case studies
• Observational studies

An example of this psychology research method would be an opinion poll to determine which presidential candidate people plan to vote for in the next election. Descriptive studies don't try to measure the effect of a variable; they seek only to describe it.

3. Relational or Correlational Research

A study that investigates the connection between two or more variables is considered relational research. The variables compared are generally already present in the group or population.

For example, a study that looks at the proportion of males and females that would purchase either a classical CD or a jazz CD would be studying the relationship between gender and music preference.

Theory vs. Hypothesis in Psychology Research

People often confuse the terms theory and hypothesis or are not quite sure of the distinctions between the two concepts. If you're a psychology student, it's essential to understand what each term means, how they differ, and how they're used in psychology research.

A theory is a well-established principle that has been developed to explain some aspect of the natural world. A theory arises from repeated observation and testing and incorporates facts, laws, predictions, and tested hypotheses that are widely accepted.

A hypothesis is a specific, testable prediction about what you expect to happen in your study. For example, an experiment designed to look at the relationship between study habits and test anxiety might have a hypothesis that states, "We predict that students with better study habits will suffer less test anxiety." Unless your study is exploratory in nature, your hypothesis should always explain what you expect to happen during the course of your experiment or research.

While the terms are sometimes used interchangeably in everyday use, the difference between a theory and a hypothesis is important when studying experimental design.

Some other important distinctions to note include:

• A theory predicts events in general terms, while a hypothesis makes a specific prediction about a specified set of circumstances.
• A theory has been extensively tested and is generally accepted, while a hypothesis is a speculative guess that has yet to be tested.

The Effect of Time on Research Methods in Psychology

There are two types of time dimensions that can be used in designing a research study:

• Cross-sectional research takes place at a single point in time. All tests, measures, or variables are administered to participants on one occasion. This type of research seeks to gather data on present conditions instead of looking at the effects of a variable over a period of time.
• Longitudinal research is a study that takes place over a period of time. Data is first collected at the beginning of the study, and may then be gathered repeatedly throughout the length of the study. Some longitudinal studies may occur over a short period of time, such as a few days, while others may take place over a period of months, years, or even decades.

The effects of aging are often investigated using longitudinal research.

Causal Relationships Between Psychology Research Variables

What do we mean when we talk about a “relationship” between variables? In psychological research, we're referring to a connection between two or more factors that we can measure or systematically vary.

One of the most important distinctions to make when discussing the relationship between variables is the meaning of causation.

A causal relationship is when one variable causes a change in another variable. These types of relationships are investigated by experimental research to determine if changes in one variable actually result in changes in another variable.

Correlational Relationships Between Psychology Research Variables

A correlation is the measurement of the relationship between two variables. These variables already occur in the group or population and are not controlled by the experimenter.

• A positive correlation is a direct relationship where, as the amount of one variable increases, the amount of a second variable also increases.
• In a negative correlation , as the amount of one variable goes up, the levels of another variable go down.

In both types of correlation, there is no evidence or proof that changes in one variable cause changes in the other variable. A correlation simply indicates that there is a relationship between the two variables.

The most important concept is that correlation does not equal causation. Many popular media sources make the mistake of assuming that simply because two variables are related, a causal relationship exists.

Psychologists use descriptive, correlational, and experimental research designs to understand behavior . In:  Introduction to Psychology . Minneapolis, MN: University of Minnesota Libraries Publishing; 2010.

Caruana EJ, Roman M, Herandez-Sanchez J, Solli P. Longitudinal studies . Journal of Thoracic Disease. 2015;7(11):E537-E540. doi:10.3978/j.issn.2072-1439.2015.10.63

University of Berkeley. Science at multiple levels . Understanding Science 101 . Published 2012.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Research Hypothesis In Psychology: Types, & Examples

Saul McLeod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

On This Page:

A research hypothesis, in its plural form “hypotheses,” is a specific, testable prediction about the anticipated results of a study, established at its outset. It is a key component of the scientific method .

Hypotheses connect theory to data and guide the research process towards expanding scientific understanding

Some key points about hypotheses:

• A hypothesis expresses an expected pattern or relationship. It connects the variables under investigation.
• It is stated in clear, precise terms before any data collection or analysis occurs. This makes the hypothesis testable.
• A hypothesis must be falsifiable. It should be possible, even if unlikely in practice, to collect data that disconfirms rather than supports the hypothesis.
• Hypotheses guide research. Scientists design studies to explicitly evaluate hypotheses about how nature works.
• For a hypothesis to be valid, it must be testable against empirical evidence. The evidence can then confirm or disprove the testable predictions.
• Hypotheses are informed by background knowledge and observation, but go beyond what is already known to propose an explanation of how or why something occurs.

Predictions typically arise from a thorough knowledge of the research literature, curiosity about real-world problems or implications, and integrating this to advance theory. They build on existing literature while providing new insight.

Types of Research Hypotheses

Alternative hypothesis.

The research hypothesis is often called the alternative or experimental hypothesis in experimental research.

It typically suggests a potential relationship between two key variables: the independent variable, which the researcher manipulates, and the dependent variable, which is measured based on those changes.

The alternative hypothesis states a relationship exists between the two variables being studied (one variable affects the other).

A hypothesis is a testable statement or prediction about the relationship between two or more variables. It is a key component of the scientific method. Some key points about hypotheses:

• Important hypotheses lead to predictions that can be tested empirically. The evidence can then confirm or disprove the testable predictions.

In summary, a hypothesis is a precise, testable statement of what researchers expect to happen in a study and why. Hypotheses connect theory to data and guide the research process towards expanding scientific understanding.

An experimental hypothesis predicts what change(s) will occur in the dependent variable when the independent variable is manipulated.

It states that the results are not due to chance and are significant in supporting the theory being investigated.

The alternative hypothesis can be directional, indicating a specific direction of the effect, or non-directional, suggesting a difference without specifying its nature. It’s what researchers aim to support or demonstrate through their study.

Null Hypothesis

The null hypothesis states no relationship exists between the two variables being studied (one variable does not affect the other). There will be no changes in the dependent variable due to manipulating the independent variable.

It states results are due to chance and are not significant in supporting the idea being investigated.

The null hypothesis, positing no effect or relationship, is a foundational contrast to the research hypothesis in scientific inquiry. It establishes a baseline for statistical testing, promoting objectivity by initiating research from a neutral stance.

Many statistical methods are tailored to test the null hypothesis, determining the likelihood of observed results if no true effect exists.

This dual-hypothesis approach provides clarity, ensuring that research intentions are explicit, and fosters consistency across scientific studies, enhancing the standardization and interpretability of research outcomes.

Nondirectional Hypothesis

A non-directional hypothesis, also known as a two-tailed hypothesis, predicts that there is a difference or relationship between two variables but does not specify the direction of this relationship.

It merely indicates that a change or effect will occur without predicting which group will have higher or lower values.

For example, “There is a difference in performance between Group A and Group B” is a non-directional hypothesis.

Directional Hypothesis

A directional (one-tailed) hypothesis predicts the nature of the effect of the independent variable on the dependent variable. It predicts in which direction the change will take place. (i.e., greater, smaller, less, more)

It specifies whether one variable is greater, lesser, or different from another, rather than just indicating that there’s a difference without specifying its nature.

For example, “Exercise increases weight loss” is a directional hypothesis.

Falsifiability

The Falsification Principle, proposed by Karl Popper , is a way of demarcating science from non-science. It suggests that for a theory or hypothesis to be considered scientific, it must be testable and irrefutable.

Falsifiability emphasizes that scientific claims shouldn’t just be confirmable but should also have the potential to be proven wrong.

It means that there should exist some potential evidence or experiment that could prove the proposition false.

However many confirming instances exist for a theory, it only takes one counter observation to falsify it. For example, the hypothesis that “all swans are white,” can be falsified by observing a black swan.

For Popper, science should attempt to disprove a theory rather than attempt to continually provide evidence to support a research hypothesis.

Can a Hypothesis be Proven?

Hypotheses make probabilistic predictions. They state the expected outcome if a particular relationship exists. However, a study result supporting a hypothesis does not definitively prove it is true.

All studies have limitations. There may be unknown confounding factors or issues that limit the certainty of conclusions. Additional studies may yield different results.

In science, hypotheses can realistically only be supported with some degree of confidence, not proven. The process of science is to incrementally accumulate evidence for and against hypothesized relationships in an ongoing pursuit of better models and explanations that best fit the empirical data. But hypotheses remain open to revision and rejection if that is where the evidence leads.

• Disproving a hypothesis is definitive. Solid disconfirmatory evidence will falsify a hypothesis and require altering or discarding it based on the evidence.
• However, confirming evidence is always open to revision. Other explanations may account for the same results, and additional or contradictory evidence may emerge over time.

We can never 100% prove the alternative hypothesis. Instead, we see if we can disprove, or reject the null hypothesis.

If we reject the null hypothesis, this doesn’t mean that our alternative hypothesis is correct but does support the alternative/experimental hypothesis.

Upon analysis of the results, an alternative hypothesis can be rejected or supported, but it can never be proven to be correct. We must avoid any reference to results proving a theory as this implies 100% certainty, and there is always a chance that evidence may exist which could refute a theory.

How to Write a Hypothesis

• Identify variables . The researcher manipulates the independent variable and the dependent variable is the measured outcome.
• Operationalized the variables being investigated . Operationalization of a hypothesis refers to the process of making the variables physically measurable or testable, e.g. if you are about to study aggression, you might count the number of punches given by participants.
• Decide on a direction for your prediction . If there is evidence in the literature to support a specific effect of the independent variable on the dependent variable, write a directional (one-tailed) hypothesis. If there are limited or ambiguous findings in the literature regarding the effect of the independent variable on the dependent variable, write a non-directional (two-tailed) hypothesis.
• Make it Testable : Ensure your hypothesis can be tested through experimentation or observation. It should be possible to prove it false (principle of falsifiability).
• Clear & concise language . A strong hypothesis is concise (typically one to two sentences long), and formulated using clear and straightforward language, ensuring it’s easily understood and testable.

Consider a hypothesis many teachers might subscribe to: students work better on Monday morning than on Friday afternoon (IV=Day, DV= Standard of work).

Now, if we decide to study this by giving the same group of students a lesson on a Monday morning and a Friday afternoon and then measuring their immediate recall of the material covered in each session, we would end up with the following:

• The alternative hypothesis states that students will recall significantly more information on a Monday morning than on a Friday afternoon.
• The null hypothesis states that there will be no significant difference in the amount recalled on a Monday morning compared to a Friday afternoon. Any difference will be due to chance or confounding factors.

More Examples

• Memory : Participants exposed to classical music during study sessions will recall more items from a list than those who studied in silence.
• Social Psychology : Individuals who frequently engage in social media use will report higher levels of perceived social isolation compared to those who use it infrequently.
• Developmental Psychology : Children who engage in regular imaginative play have better problem-solving skills than those who don’t.
• Clinical Psychology : Cognitive-behavioral therapy will be more effective in reducing symptoms of anxiety over a 6-month period compared to traditional talk therapy.
• Cognitive Psychology : Individuals who multitask between various electronic devices will have shorter attention spans on focused tasks than those who single-task.
• Health Psychology : Patients who practice mindfulness meditation will experience lower levels of chronic pain compared to those who don’t meditate.
• Organizational Psychology : Employees in open-plan offices will report higher levels of stress than those in private offices.
• Behavioral Psychology : Rats rewarded with food after pressing a lever will press it more frequently than rats who receive no reward.

Hypothesis vs. Theory

What's the difference.

Hypothesis and theory are two terms commonly used in scientific research, but they have distinct meanings and purposes. A hypothesis is a proposed explanation or prediction for a specific phenomenon or observation. It is based on limited evidence and serves as a starting point for further investigation. In contrast, a theory is a well-substantiated explanation that has been extensively tested and supported by a wide range of evidence. It is a comprehensive framework that explains a broad set of phenomena and is widely accepted within the scientific community. While a hypothesis is more tentative and subject to change, a theory represents a higher level of confidence and understanding in the scientific field.

Further Detail

Introduction.

In the realm of scientific inquiry, hypotheses and theories play crucial roles in the development and understanding of knowledge. While both are essential components of the scientific method, they differ in their scope, level of evidence, and the degree of generalization they offer. This article aims to explore and compare the attributes of hypotheses and theories, shedding light on their distinct characteristics and their contributions to scientific progress.

Hypothesis: The Foundation of Scientific Inquiry

A hypothesis is a proposed explanation or prediction for a specific phenomenon or observation. It serves as the initial step in the scientific method, where researchers formulate educated guesses based on existing knowledge and observations. Hypotheses are typically testable and falsifiable, allowing scientists to design experiments or gather data to either support or reject them.

One key attribute of a hypothesis is its specificity. It focuses on a particular aspect of a phenomenon and aims to explain or predict it. For example, a hypothesis might propose that increased exposure to sunlight leads to higher vitamin D levels in humans. This hypothesis is specific to the relationship between sunlight and vitamin D, providing a clear direction for further investigation.

Furthermore, hypotheses are often based on preliminary evidence or observations. They are formulated to address gaps in knowledge or to explain puzzling phenomena. Hypotheses can be derived from existing theories or can emerge from exploratory research. They serve as the foundation for scientific inquiry, guiding researchers towards the collection of empirical evidence.

It is important to note that a hypothesis is not considered a proven fact, even if it is supported by initial evidence. It requires rigorous testing and validation through experimentation and data analysis. If a hypothesis withstands repeated testing and scrutiny, it may evolve into a theory.

Theory: A Comprehensive Explanation

A theory, in the scientific context, is a well-substantiated explanation that encompasses a wide range of observations, experiments, and hypotheses. Unlike a hypothesis, a theory is supported by a substantial body of evidence and has withstood extensive testing and scrutiny. Theories provide a comprehensive framework for understanding natural phenomena and have a higher level of generalization compared to hypotheses.

One key attribute of a theory is its ability to explain and predict a broad range of related phenomena. For example, the theory of evolution by natural selection explains the diversity of life on Earth, the fossil record, and the similarities between different species. Theories are built upon a foundation of multiple lines of evidence, including experimental data, observational studies, and mathematical models.

Theories are also subject to revision and refinement as new evidence emerges. However, this does not undermine their validity or significance. The process of scientific inquiry involves constantly challenging and refining existing theories to accommodate new findings. Theories are not static, but rather dynamic frameworks that adapt to incorporate new knowledge.

Moreover, theories are widely accepted within the scientific community due to their robustness and explanatory power. They have undergone rigorous peer review and scrutiny, ensuring that they meet the highest standards of scientific integrity. Theories provide a solid foundation for further research and serve as a basis for the development of new hypotheses.

Comparing Hypotheses and Theories

While hypotheses and theories share the common goal of explaining natural phenomena, they differ in several key attributes. Let's explore some of the main points of comparison:

Scope and Generalization

Hypotheses are typically narrow in scope, focusing on specific aspects of a phenomenon. They aim to explain or predict a particular observation or relationship. In contrast, theories have a broader scope and offer a higher level of generalization. They provide comprehensive explanations that encompass multiple phenomena and observations.

Evidence and Testing

Hypotheses are formulated based on preliminary evidence or observations. They serve as starting points for scientific investigation and require empirical testing to determine their validity. Hypotheses are often tested through experiments, data analysis, or observational studies. Theories, on the other hand, are supported by a substantial body of evidence. They have withstood extensive testing and scrutiny, incorporating multiple lines of evidence from various sources.

Level of Certainty

Due to their preliminary nature, hypotheses do not offer a high level of certainty. They are educated guesses that require further testing and validation. In contrast, theories provide a higher level of certainty and confidence. They are well-substantiated explanations that have been extensively tested and supported by a wide range of evidence.

Development and Evolution

Hypotheses are often derived from existing theories or emerge from exploratory research. They serve as the initial step in scientific inquiry and can evolve into theories if supported by substantial evidence. Theories, on the other hand, are the result of extensive research, testing, and refinement. They are dynamic frameworks that adapt to incorporate new evidence and insights.

Acceptance and Consensus

While hypotheses are subject to individual interpretation and may vary among researchers, theories are widely accepted within the scientific community. Theories have undergone rigorous peer review and scrutiny, ensuring a high level of consensus among experts. They provide a solid foundation for scientific understanding and guide further research.

In summary, hypotheses and theories are integral components of the scientific method, each serving distinct roles in the pursuit of knowledge. Hypotheses provide specific explanations or predictions for phenomena and act as the initial step in scientific inquiry. They require empirical testing and validation to determine their validity. Theories, on the other hand, offer comprehensive explanations that encompass a wide range of observations and have withstood extensive testing. They provide a higher level of generalization and serve as the foundation for scientific understanding. While hypotheses and theories differ in their scope, level of evidence, and generalization, they both contribute to the advancement of scientific knowledge and our understanding of the natural world.

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4.1 Phenomena and Theories

Learning objectives.

• Define the terms phenomenon and theory and distinguish clearly between them.
• Explain the purposes of scientific theories.
• Explain why there are usually many plausible theories for any set of phenomena.

A phenomenon (plural, phenomena ) is a general result that has been observed reliably in systematic empirical research. In essence, it is an established answer to a research question. Some phenomena we have encountered in this book are that expressive writing improves health, women do not talk more than men, and cell phone usage impairs driving ability. Some others are that dissociative identity disorder (formerly called multiple personality disorder) increased greatly in prevalence during the late 20th century, people perform better on easy tasks when they are being watched by others (and worse on difficult tasks), and people recall items presented at the beginning and end of a list better than items presented in the middle.

Some Famous Psychological Phenomena

Phenomena are often given names by their discoverers or other researchers, and these names can catch on and become widely known. The following list is a small sample of famous phenomena in psychology.

• Blindsight. People with damage to their visual cortex are often able to respond to visual stimuli that they do not consciously see.
• Bystander effect. The more people who are present at an emergency situation, the less likely it is that any one of them will help.
• Fundamental attribution error. People tend to explain others’ behavior in terms of their personal characteristics as opposed to the situation they are in.
• McGurk effect. When audio of a basic speech sound is combined with video of a person making mouth movements for a different speech sound, people often perceive a sound that is intermediate between the two. For a demonstration, see http://www.faculty.ucr.edu/~rosenblu/VSMcGurk.html .
• Own-race effect. People recognize faces of people of their own race more accurately than faces of people of other races.
• Placebo effect. Placebos (fake psychological or medical treatments) often lead to improvements in people’s symptoms and functioning.
• Mere exposure effect. The more often people have been exposed to a stimulus, the more they like it—even when the stimulus is presented subliminally.
• Serial position effect. Stimuli presented near the beginning and end of a list are remembered better than stimuli presented in the middle. For a demonstration, see http://cat.xula.edu/thinker/memory/working/serial .
• Spontaneous recovery. A conditioned response that has been extinguished often returns with no further training after the passage of time.

Although an empirical result might be referred to as a phenomenon after being observed only once, this term is more likely to be used for results that have been replicated. Replication means conducting a study again—either exactly as it was originally conducted or with modifications—to be sure that it produces the same results. Individual researchers usually replicate their own studies before publishing them. Many empirical research reports include an initial study and then one or more follow-up studies that replicate the initial study with minor modifications. Particularly interesting results come to the attention of other researchers who conduct their own replications. The positive effect of expressive writing on health and the negative effect of cell phone usage on driving ability are examples of phenomena that have been replicated many times by many different researchers.

Sometimes a replication of a study produces results that differ from the results of the initial study. This could mean that the results of the initial study or the results of the replication were a fluke—they occurred by chance and do not reflect something that is generally true. In either case, additional replications would be likely to resolve this. A failure to produce the same results could also mean that the replication differed in some important way from the initial study. For example, early studies showed that people performed a variety of tasks better and faster when they were watched by others than when they were alone. Some later replications, however, showed that people performed worse when they were watched by others. Eventually researcher Robert Zajonc identified a key difference between the two types of studies. People seemed to perform better when being watched on highly practiced tasks but worse when being watched on relatively unpracticed tasks (Zajonc, 1965). These two phenomena have now come to be called social facilitation and social inhibition.

What Is a Theory?

A theory is a coherent explanation or interpretation of one or more phenomena. Although theories can take a variety of forms, one thing they have in common is that they go beyond the phenomena they explain by including variables, structures, processes, functions, or organizing principles that have not been observed directly. Consider, for example, Zajonc’s theory of social facilitation and social inhibition. He proposed that being watched by others while performing a task creates a general state of physiological arousal, which increases the likelihood of the dominant (most likely) response. So for highly practiced tasks, being watched increases the tendency to make correct responses, but for relatively unpracticed tasks, being watched increases the tendency to make incorrect responses. Notice that this theory—which has come to be called drive theory—provides an explanation of both social facilitation and social inhibition that goes beyond the phenomena themselves by including concepts such as “arousal” and “dominant response,” along with processes such as the effect of arousal on the dominant response.

Outside of science, referring to an idea as a theory often implies that it is untested—perhaps no more than a wild guess. In science, however, the term theory has no such implication. A theory is simply an explanation or interpretation of a set of phenomena. It can be untested, but it can also be extensively tested, well supported, and accepted as an accurate description of the world by the scientific community. The theory of evolution by natural selection, for example, is a theory because it is an explanation of the diversity of life on earth—not because it is untested or unsupported by scientific research. On the contrary, the evidence for this theory is overwhelmingly positive and nearly all scientists accept its basic assumptions as accurate. Similarly, the “germ theory” of disease is a theory because it is an explanation of the origin of various diseases, not because there is any doubt that many diseases are caused by microorganisms that infect the body.

In addition to theory , researchers in psychology use several related terms to refer to their explanations and interpretations of phenomena. A perspective is a broad approach—more general than a theory—to explaining and interpreting phenomena. For example, researchers who take a biological perspective tend to explain phenomena in terms of genetics or nervous and endocrine system structures and processes, while researchers who take a behavioral perspective tend to explain phenomena in terms of reinforcement, punishment, and other external events. A model is a precise explanation or interpretation of a specific phenomenon—often expressed in terms of equations, computer programs, or biological structures and processes. A hypothesis can be an explanation that relies on just a few key concepts—although this term more commonly refers to a prediction about a new phenomenon based on a theory (see Section 4.3 “Using Theories in Psychological Research” ). Adding to the confusion is the fact that researchers often use these terms interchangeably. It would not be considered wrong to refer to the drive theory as the drive model or even the drive hypothesis. And the biopsychosocial model of health psychology—the general idea that health is determined by an interaction of biological, psychological, and social factors—is really more like a perspective as defined here. Keep in mind, however, that the most important distinction remains that between observations and interpretations.

What Are Theories For?

Of course, scientific theories are meant to provide accurate explanations or interpretations of phenomena. But there must be more to it than this. Consider that a theory can be accurate without being very useful. To say that expressive writing helps people “deal with their emotions” might be accurate as far as it goes, but it seems too vague to be of much use. Consider also that a theory can be useful without being entirely accurate. Figure 4.2 “Representation of the Multistore Model of Human Memory” is a representation of the classic multistore model of human memory, which is still cited by researchers and discussed in textbooks despite the fact that it is now known to be inaccurate in a number of ways (Izawa, 1999). These two examples suggest that theories have purposes other than simply providing accurate explanations or interpretations. Here we look at three additional purposes of theories: the organization of known phenomena, the prediction of outcomes in new situations, and the generation of new research.

Figure 4.2 Representation of the Multistore Model of Human Memory

In the multistore model of human memory, information from the environment passes through a sensory store on its way to a short-term store, where it can be rehearsed, and then to a long-term store, where it can be stored and retrieved much later. This theory has been extremely successful at organizing old phenomena and predicting new ones.

Organization

One important purpose of scientific theories is to organize phenomena in ways that help people think about them clearly and efficiently. The drive theory of social facilitation and social inhibition, for example, helps to organize and make sense of a large number of seemingly contradictory results. The multistore model of human memory efficiently summarizes many important phenomena: the limited capacity and short retention time of information that is attended to but not rehearsed, the importance of rehearsing information for long-term retention, the serial-position effect, and so on. Or consider a classic theory of intelligence represented by Figure 4.3 “Representation of One Theory of Intelligence” . According to this theory, intelligence consists of a general mental ability, g , plus a small number of more specific abilities that are influenced by g (Neisset et al., 1996). Although there are other theories of intelligence, this one does a good job of summarizing a large number of statistical relationships between tests of various mental abilities. This includes the fact that tests of all basic mental abilities tend to be somewhat positively correlated and the fact that certain subsets of mental abilities (e.g., reading comprehension and analogy completion) are more positively correlated than others (e.g., reading comprehension and arithmetic).

Figure 4.3 Representation of One Theory of Intelligence

In this theory of intelligence, a general mental ability ( g ) influences each of three more specific mental abilities. Theories of this type help to organize a large number of statistical relationships among tests of various mental abilities.

Thus theories are good or useful to the extent that they organize more phenomena with greater clarity and efficiency. Scientists generally follow the principle of parsimony , which holds that a theory should include only as many concepts as are necessary to explain or interpret the phenomena of interest. Simpler, more parsimonious theories organize phenomena more efficiently than more complex, less parsimonious theories.

A second purpose of theories is to allow researchers and others to make predictions about what will happen in new situations. For example, a gymnastics coach might wonder whether a student’s performance is likely to be better or worse during a competition than when practicing alone. Even if this particular question has never been studied empirically, Zajonc’s drive theory suggests an answer. If the student generally performs with no mistakes, she is likely to perform better during competition. If she generally performs with many mistakes, she is likely to perform worse.

In clinical psychology, treatment decisions are often guided by theories. Consider, for example, dissociative identity disorder (formerly called multiple personality disorder). The prevailing scientific theory of dissociative identity disorder is that people develop multiple personalities (also called alters) because they are familiar with this idea from popular portrayals (e.g., the movie Sybil ) and because they are unintentionally encouraged to do so by their clinicians (e.g., by asking to “meet” an alter). This theory implies that rather than encouraging patients to act out multiple personalities, treatment should involve discouraging them from doing this (Lilienfeld & Lynn, 2003).

Generation of New Research

A third purpose of theories is to generate new research by raising new questions. Consider, for example, the theory that people engage in self-injurious behavior such as cutting because it reduces negative emotions such as sadness, anxiety, and anger. This theory immediately suggests several new and interesting questions. Is there, in fact, a statistical relationship between cutting and the amount of negative emotions experienced? Is it causal? If so, what is it about cutting that has this effect? Is it the pain, the sight of the injury, or something else? Does cutting affect all negative emotions equally?

Notice that a theory does not have to be accurate to serve this purpose. Even an inaccurate theory can generate new and interesting research questions. Of course, if the theory is inaccurate, the answers to the new questions will tend to be inconsistent with the theory. This will lead researchers to reevaluate the theory and either revise it or abandon it for a new one. And this is how scientific theories become more detailed and accurate over time.

Multiple Theories

At any point in time, researchers are usually considering multiple theories for any set of phenomena. One reason is that because human behavior is extremely complex, it is always possible to look at it from different perspectives. For example, a biological theory of sexual orientation might focus on the role of sex hormones during critical periods of brain development, while a sociocultural theory might focus on cultural factors that influence how underlying biological tendencies are expressed. A second reason is that—even from the same perspective—there are usually different ways to “go beyond” the phenomena of interest. For example, in addition to the drive theory of social facilitation and social inhibition, there is another theory that explains them in terms of a construct called “evaluation apprehension”—anxiety about being evaluated by the audience. Both theories go beyond the phenomena to be interpreted, but they do so by proposing somewhat different underlying processes.

Different theories of the same set of phenomena can be complementary—with each one supplying one piece of a larger puzzle. A biological theory of sexual orientation and a sociocultural theory of sexual orientation might accurately describe different aspects of the same complex phenomenon. Similarly, social facilitation could be the result of both general physiological arousal and evaluation apprehension. But different theories of the same phenomena can also be competing in the sense that if one is accurate, the other is probably not. For example, an alternative theory of dissociative identity disorder—the posttraumatic theory—holds that alters are created unconsciously by the patient as a means of coping with sexual abuse or some other traumatic experience. Because the sociocognitive theory and the posttraumatic theories attribute dissociative identity disorder to fundamentally different processes, it seems unlikely that both can be accurate. See Note 4.10 “Where Do Multiple Personalities Come From?” for more on these competing theories.

The fact that there are multiple theories for any set of phenomena does not mean that any theory is as good as any other or that it is impossible to know whether a theory provides an accurate explanation or interpretation. On the contrary, scientists are continually comparing theories in terms of their ability to organize phenomena, predict outcomes in new situations, and generate research. Those that fare poorly are assumed to be less accurate and are abandoned, while those that fare well are assumed to be more accurate and are retained and compared with newer—and hopefully better—theories. Although scientists generally do not believe that their theories ever provide perfectly accurate descriptions of the world, they do assume that this process produces theories that come closer and closer to that ideal.

Where Do Multiple Personalities Come From?

The literature on dissociative identity disorder (DID) features two competing theories. The sociocognitive theory is that DID comes about because patients are aware of the disorder, know its characteristic features, and are encouraged to take on multiple personalities by their therapists. The posttraumatic theory is that multiple personalities develop as a way of coping with sexual abuse or some other trauma. There are now several lines of evidence that support the sociocognitive model over the posttraumatic model (Lilienfeld & Lynn, 2003).

• Diagnosis of DID greatly increased after the release of the book and film Sybil —about a woman with DID—in the 1970s.
• DID is extremely rare outside of North America.
• A very small percentage of therapists are responsible for diagnosing the vast majority of cases of DID.
• The literature on treating DID includes many practices that encourage patients to act out multiple personalities (e.g., having a bulletin board on which personalities can leave messages for each other).
• Normal people can easily re-create the symptoms of DID with minimal suggestion in simulated clinical interviews.

Key Takeaways

• Scientists distinguish between phenomena, which are their systematic observations, and theories, which are their explanations or interpretations of phenomena.
• In addition to providing accurate explanations or interpretations, scientific theories have three basic purposes. They organize phenomena, allow people to predict what will happen in new situations, and help generate new research.
• Researchers generally consider multiple theories for any set of phenomena. Different theories of the same set of phenomena can be complementary or competing.
• Practice: Think of at least three different theories to explain the fact that married people tend to report greater levels of happiness than unmarried people.

Practice: Find a recent article in a professional journal and do two things:

• Identify the primary phenomenon of interest.
• Identify the theory or theories used to explain or interpret that phenomenon.
• Discussion: Can a theory be useful even if it is inaccurate? How?

Izawa, C. (Ed.) (1999). On human memory: Evolution, progress, and reflections on the 30th anniversary of the Atkinson-Shiffrin model . Mahwah, NJ: Erlbaum.

Lilienfeld, S. O., & Lynn, S. J. (2003). Dissociative identity disorder: Multiplepersonalities, multiple controversies. In S. O. Lilienfeld, S. J. Lynn, & J. M. Lohr (Eds.), Science and pseudoscience in clinical psychology (pp. 109–142). New York, NY: Guilford Press.

Neisser, U., Boodoo, G., Bouchard, T. J., Boykin, A. W., Brody, N., Ceci,…Urbina, S. (1996). Intelligence: Knowns and unknowns. American Psychologist, 51 , 77–101.

Zajonc, R. B. (1965). Social facilitation. Science, 149 , 269–274.

Research Methods in Psychology Copyright © 2016 by University of Minnesota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

“Theory” vs. “Hypothesis”: What Is The Difference?

Chances are you’ve heard of the TV show The Big Bang Theory . Lots of people love this lighthearted sitcom for its quirky characters and their relationships, but others haven’t even given the series a chance for one reason: they don’t like science and assume the show is boring.

However, it only takes a few seconds with Sheldon and Penny to disprove this assumption and realize that this theory ab0ut The Big Bang Theory is wrong—it isn’t a scientific snoozefest.

But wait: is it a theory or a  hypothesis about the show that leads people astray? And would the actual big bang theory— the one that refers to the beginning of the universe—mean the same thing as a big bang hypothesis ?

Let’s take a closer look at theory and hypothesis to nail down what they mean.

What does theory mean?

As a noun, a theory is a group of tested general propositions “commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena .” This is what is known as a scientific   theory , which by definition is “an understanding that is based on already tested data or results .” Einstein’s theory of relativity and the  theory of evolution are both examples of such tested propositions .

Theory is also defined as a proposed explanation you might make about your own life and observations, and it’s one “whose status is still conjectural and subject to experimentation .” For example:  I’ve got my own theories about why he’s missing his deadlines all the time.  This example refers to an idea that has not yet been proven.

There are other uses of the word theory as well.

• In this example,  theory is “a body of principles or theorems belonging to one subject.” It can be a branch of science or art that deals with its principles or methods .
• For example: when she started to follow a new parenting theory based on a trendy book, it caused a conflict with her mother, who kept offering differing opinions .

First recorded in 1590–1600, theory originates from the Late Latin theōria , which stems from the Greek theōría. Synonyms for theory include approach , assumption , doctrine , ideology , method , philosophy , speculation , thesis , and understanding .

What does hypothesis mean?

Hypothesis is a noun that means “a proposition , or set of propositions, set forth as an explanation” that describe “some specified group of phenomena.” Sounds familiar to theory , no?

But, unlike a theory , a scientific  hypothesis is made before testing is done and isn’t based on results. Instead, it is the basis for further investigation . For example: her working hypothesis is that this new drug also has an unintended effect on the heart, and she is curious what the clinical trials  will show .

Hypothesis also refers to “a proposition assumed as a premise in an argument,” or “mere assumption or guess.” For example:

• She decided to drink more water for a week to test out her hypothesis that dehydration was causing her terrible headaches.
• After a night of her spouse’s maddening snoring, she came up with the hypothesis that sleeping on his back was exacerbating the problem.

Hypothesis was first recorded around 1590–1600 and originates from the Greek word hypóthesis (“basis, supposition”). Synonyms for hypothesis include: assumption , conclusion , conjecture , guess , inference , premise , theorem , and thesis .

How to use each

Although theory in terms of science is used to express something based on extensive research and experimentation, typically in everyday life, theory is used more casually to express an educated guess.

So in casual language,  theory and hypothesis are more likely to be used interchangeably to express an idea or speculation .

In most everyday uses, theory and hypothesis convey the same meaning. For example:

• Her opinion is just a theory , of course. She’s just guessing.
• Her opinion is just a hypothesis , of course. She’s just guessing.

It’s important to remember that a scientific   theory is different. It is based on tested results that support or substantiate it, whereas a hypothesis is formed before the research.

For example:

• His  hypothesis  for the class science project is that this brand of plant food is better than the rest for helping grass grow.
• After testing his hypothesis , he developed a new theory based on the experiment results: plant food B is actually more effective than plant food A in helping grass grow.

In these examples, theory “doesn’t mean a hunch or a guess,” according to Kenneth R. Miller, a cell biologist at Brown University. “A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”

So if you have a concept that is based on substantiated research, it’s a theory .

But if you’re working off of an assumption that you still need to test, it’s a hypothesis .

So remember, first comes a hypothesis , then comes theory . Now who’s ready for a  Big Bang Theory marathon?

Now that you’ve theorized and hypothesized through this whole article … keep testing your judgment (Or is it judgement?). Find out the correct spelling here!

Or find out the difference between these two common issues below!

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