Source: General Psychology, The Ohio State University
Difficulty: Introductory | Prerequisites: None
Tags: scientific method, dialectic, theory, hypothesis, operational definition, descriptive research, case study, naturalistic observation, survey method, observer bias, sampling bias, Phineas Gage, psychology research methods
This is where psychology stops being a collection of interesting ideas and starts being a science. Unit 2 covers how psychologists gather evidence, from the logic of the scientific method down to specific research designs like case studies and surveys. If you are coming in cold, know that psychology treats human behaviour as something you can study systematically, not just speculate about. Everything in later units (perception, memory, abnormal psych) rests on these methods, so getting comfortable here pays dividends for the rest of the course.
Psychologists use the scientific method to move from broad theories to testable hypotheses, then collect data to support or revise those theories. Descriptive research (case studies, naturalistic observation, surveys) describes what is happening but cannot prove cause and effect. Each method comes with its own set of biases you need to recognise.
Dialectic
The process of arriving at truth through thesis, antithesis, and synthesis. You propose an idea, consider the opposing idea, and combine the strongest elements of both into a new understanding.
In simple terms, think of it as an intellectual argument where two opposing views clash and produce a better, combined answer.
Theory
A broad explanation that organises and predicts observations about the world. In psychology, a theory is not a guess; it is a well-supported framework built from evidence.
In simple terms, a theory is the "big picture story" that ties lots of individual findings together.
Hypothesis
A specific, testable prediction derived from a theory. It states what you expect to happen under particular conditions.
In simple terms, this is the "if... then..." statement you can test with an experiment or study.
Operational definition
A precise explanation of the terms used in your research, stated in measurable terms. It tells other researchers exactly what you mean by each variable.
In simple terms, it turns a vague idea ("productivity") into something you can count or observe ("number of tasks completed per hour").
Scientific method
A self-correcting process in which a researcher considers a topic, develops a theory, creates a hypothesis, and then conducts research to test it. Results feed back into the theory, refining or replacing it.
In simple terms, this is the loop of "wonder, guess, test, learn, repeat" that keeps science honest.
Descriptive research
Research that describes people, events, and behaviours without establishing cause and effect. It answers "what is happening" rather than "why."
In simple terms, you are taking a snapshot, not running an experiment.
Case study
An in-depth examination of all aspects of a single case, which may be one person or one group. Famous example: Phineas Gage.
In simple terms, it is a deep dive into one particular instance to learn as much as possible from it.
Naturalistic observation
Observing a person or animal in the environment in which they naturally live, without interference. Jane Goodall's work with chimpanzees is a classic example.
In simple terms, you watch behaviour "in the wild" rather than in a lab.
Observer effect
The phenomenon where the act of observing changes the behaviour being observed. When naturalistic observation goes wrong, this is usually why.
In simple terms, people (and animals) behave differently when they know they are being watched.
Observer bias
When observers see what they expect or want to see, rather than what is there. Their expectations colour their recording of behaviour.
In simple terms, your own assumptions can filter what you notice.
Survey method
Using public polling techniques (questionnaires, interviews) to answer psychological questions across a large group.
In simple terms, you ask lots of people the same questions and look for patterns in their answers.
Sampling bias
When the sample used in a study is unrepresentative of the population, whether because it is too small, too homogeneous, or selected in a skewed way.
In simple terms, if everyone in your survey is a university student aged 19, you cannot claim your findings apply to all humans.
Courtesy bias
When participants in a survey say what they think the researcher wants to hear, rather than giving their true response.
In simple terms, people are polite, and that politeness can contaminate your data.
Response bias
When not all surveys are returned, meaning the people who did respond may differ systematically from those who did not.
In simple terms, the people who bother to reply might already be different from those who bin the questionnaire.
The scientific method is a cycle, not a straight line: theory leads to hypothesis, hypothesis leads to research, and research feeds back into the theory.
A theory is broad; a hypothesis is specific and testable.
Operational definitions are essential because they ensure everyone is measuring the same thing. Without them, "productivity" could mean anything.
Worked example from the course:
Theory: People are more productive in a cleaner environment.
Hypothesis: If placed in a disorganised environment, people will have trouble staying productive.
Operational definitions:
Productivity: state or quality of work
Clean environment: not cluttered, organised, and neat
Descriptive methods let you characterise behaviour but they cannot tell you why it happens. Three main types appear in this unit:
Case studies provide extraordinary depth on a single subject. They are brilliant for rare phenomena (brain injuries, unusual disorders) but their findings may not generalise to the wider population.
Naturalistic observation preserves ecological validity, meaning you see behaviour as it happens in real life. The trade-off is reduced control over variables and vulnerability to the observer effect.
Surveys give you breadth across many participants. The trade-off is that you rely on self-report, which is vulnerable to courtesy bias, sampling bias, and response bias.
In 1848, an iron rod was driven through Phineas Gage's skull. He survived, was conscious and coherent after the incident, and eventually left hospital after recovering from an infection. However, people around him noticed stark personality changes: he became aggressive and developed alcoholism. This is attributed to severe damage to his frontal lobe. Gage's case is one of the primary reasons scientists began studying the connection between brain structure and behaviour.
Naturalistic observation is the backbone of wildlife biology and ethology (Jane Goodall's chimpanzee research is the textbook example). Surveys underpin political polling, market research, and public health monitoring. Case studies remain central in clinical psychology, where understanding one patient in depth can reveal patterns that large-scale studies miss.
Students often think "descriptive research" is less important or less rigorous than experiments. It is not less rigorous; it simply answers a different kind of question.
Students confuse the observer effect (behaviour changes because of observation) with observer bias (the researcher's perception is skewed). These are two distinct problems.
A case study is sometimes treated as proof of a general rule. It is not. Phineas Gage tells us something important about the frontal lobe, but one person's injury cannot establish a universal law.
Students sometimes assume surveys give you cause-and-effect information. They do not; surveys are descriptive.
⚠️ Be able to distinguish between a theory, a hypothesis, and an operational definition. Exam questions often give you a scenario and ask you to identify which is which.
⚠️ Know the three types of descriptive research and be able to name a strength and a limitation of each.
⚠️ Phineas Gage is a frequently tested example. Know what happened, what it revealed about the frontal lobe, and why it qualifies as a case study.
⚠️ Be ready to identify types of bias (observer bias, sampling bias, courtesy bias, response bias) from a described scenario.
True or False: A hypothesis is broader and less specific than a theory.
Fill in the blank: The type of descriptive research that involves watching subjects in their natural environment is called __________.
True or False: Courtesy bias occurs when researchers see what they expect to see.
Fill in the blank: Phineas Gage's personality changes were attributed to damage to his __________ lobe.
True or False: Descriptive research can establish cause and effect.
Answers: 1. False (a hypothesis is more specific). 2. Naturalistic observation. 3. False (that is observer bias; courtesy bias is when participants say what the researcher wants to hear). 4. Frontal. 5. False.
Q: A researcher watches children on a playground without interacting with them. What type of research method is this, and what is one key limitation?
A: This is naturalistic observation. One key limitation is the observer effect: the children may behave differently if they notice they are being watched.
Q: What are operational definitions, and why are they important in psychological research?
A: Operational definitions are precise, measurable explanations of the terms used in a study. They are important because they allow other researchers to replicate the study and ensure everyone is measuring the same construct.
Q: Explain how the case of Phineas Gage contributed to our understanding of the brain.
A: After an iron rod destroyed much of Gage's frontal lobe, his personality changed dramatically (becoming aggressive and developing alcoholism), while his basic cognitive functions remained largely intact. This demonstrated that specific brain regions are linked to specific aspects of behaviour and personality, helping to launch the study of brain-behaviour relationships.
Q: A survey on student satisfaction is emailed to 5,000 students, but only 200 respond. What type of bias might affect the results?
A: Response bias. The 200 students who chose to respond may differ systematically from the 4,800 who did not (e.g., they may feel more strongly about the topic), making the results unrepresentative.
This material connects directly to the next sections on correlational research and experiments (also in Unit 2), which build on these foundations by adding tools for measuring relationships and testing causation. The Phineas Gage case connects to later units on the brain and biological psychology. Survey methodology reappears when the course covers social psychology and attitudes.
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