Before conducting a scientific experiment, researchers are required to formulate a specific, testable hypothesis. This explicit prediction serves as the foundation for the study, establishing exactly what relationship or effect the experiment is designed to measure and evaluate.

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A hypothesis is a specific prediction regarding the outcome of a particular scientific study. In the hypothetico-deductive method, hypotheses are derived directly from broader theories and are then tested empirically to support or reevaluate those theories. Importantly, disconfirming a hypothesis does not necessarily mean that the underlying theory from which it was derived has been disproved.

Hypothesis

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

In a scientific context, deductive reasoning starts with a general premise or hypothesis and uses it to derive specific, logical conclusions about the real world. This method is employed by scientists to empirically test their hypotheses. The validity of the conclusions reached is entirely dependent on the correctness of the initial hypothesis; a correct hypothesis will lead to correct conclusions, while an incorrect one can result in conclusions that are logical but factually wrong.

Deductive Reasoning

Science is a process of continuous revision. It is fruitful to look for ways to understand the exceptions to existing theories. This can spark new ideas for hypotheses, which can allow for further understanding of the subject.

Generating Hypotheses

An example of a hypothesis that cannot be scientifically tested is the claim that 'a bird sings because it is happy.' This hypothesis is untestable because there is no objective way to measure a bird's happiness. Scientific inquiry requires phenomena to be perceivable and measurable. A testable alternative could focus on the bird's brain state, as brain activity is a measurable phenomenon.

Example of a Non-Testable Hypothesis

A hypothesis is frequently structured as an 'if-then' statement to establish a clear, testable prediction. For example, a student might form the hypothesis: 'If I study all night, then I will get a passing grade on the test.' This format explicitly connects a specific action (studying all night) with a measurable outcome (a passing grade).

Example of a Hypothesis

The process of testing specific hypotheses is fundamental to the evolution of scientific theories. When individual hypotheses are empirically evaluated, the results—whether they support or contradict the hypothesis—are used to modify and refine the broader theories from which they were derived. This iterative cycle ensures that scientific theories are dynamic and continuously updated to reflect real-world evidence.

Role of Hypothesis Testing in Theory Refinement

Scientific hypotheses originate from two primary sources. They can emerge from direct, real-world observations, where a researcher notices a pattern or potential relationship. Alternatively, they can be developed through a thorough review of existing research and established theories, identifying gaps in knowledge or proposing new connections.

Sources of Hypotheses: Observation and Prior Research

The scientific standard for establishing that one variable (X) causes another (Y) involves conducting a controlled experiment. In such an experiment, researchers intentionally change X while observing the resulting impact on Y, ensuring that other factors are held constant to confidently attribute the change in Y to the change in X.

The Scientific Standard for Establishing Causality: Controlled Experiments

A researcher is investigating the connection between the amount of time spent on a social media app and users' self-reported levels of happiness. The researcher starts with the general idea that excessive social media use might negatively affect well-being. Which of the following statements represents the most effective and scientifically testable hypothesis for an experiment on this topic?

Scientific theories and hypotheses share a fundamental logical connection framed as an 'if-then' relationship. When a researcher derives a hypothesis from a theory, they are essentially stating: 'If this specific theory is accurate, then this particular observable phenomenon should occur.' For instance, if drive theory is correct, then one would expect insects to run faster in the presence of others. This deductive structure not only clarifies the testable prediction but also serves as an effective strategy for generating compelling research questions.

The 'If-Then' Relationship between Theories and Hypotheses

Among the strongest hypotheses are those formulated to distinguish between competing scientific theories. In this scenario, researchers identify two theories that offer conflicting explanations for the same phenomenon. They then design a study and derive a single hypothesis where each theory implies a mutually exclusive outcome. Because the predictions are opposite, observing the study's results will confirm one theory's prediction while simultaneously disconfirming the alternative.

Testing Competing Theories with Hypotheses

An effective scientific hypothesis typically demonstrates three fundamental characteristics that allow it to be rigorously evaluated through empirical investigation. First, it must be testable and falsifiable, meaning it can be investigated and potentially disproven. Second, it must be logical, meaning it is informed by structured reasoning, existing theories, or prior observations. Third, it must be positive, actively asserting that a specific effect or relationship exists rather than claiming that it does not.

Characteristics of a Good Hypothesis

The scientific research process functions as a continuous cycle that starts with an overarching theory, leading to the generation of a specific hypothesis. Following this, data is collected, analyzed, and summarized to report findings. These results ultimately decide whether the initial theory is confirmed or if it requires modification. If modified, the updated theory acts as the basis for new hypotheses, thereby sustaining the ongoing cycle of scientific investigation.

The Cyclical Process of Scientific Inquiry

The James-Lange theory of emotion can serve as a basis for generating a testable hypothesis. Because the theory states that physiological arousal is a prerequisite for experiencing an emotion, a derived hypothesis could predict that a person who is completely unaware of their physiological arousal when exposed to a frightening stimulus—such as an aggressive snake—will not feel fear.

Deriving a Hypothesis from the James-Lange Theory

The scientific community's reliance on falsifiability instills significant confidence in the knowledge generated by scientific research. Because scientific claims must be testable, information typically undergoes rigorous and repeated testing before it is widely accepted.

Falsifiability and Confidence in Scientific Research

Requirement of a Hypothesis for Scientific Experiments

An a-theoretical hypothesis is a specific prediction that is not derived from an existing, broader theory. This often occurs when a research question is highly original, requiring researchers to formulate a hypothesis, collect data, and make observations first before a broader explanatory theory can be developed.

A-theoretical Hypothesis

A variable is any quantity, quality, or characteristic that can change or vary across different individuals, situations, or over time. In psychological research, some variables are straightforward and simple to measure, such as age or height, while others are more complex and require careful operational definition to be studied empirically.

Variable

In research, a population is the entire, often very large, group of individuals that researchers are interested in studying and drawing conclusions about. Depending on the researcher's goals, a population could be as broad as all human beings or as specific as all American teenagers, children with autism, or professional athletes.

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