Good thinking: an open-minded and objective approach of the scientific method that uses the principle of parsimony.

Hume: Scottish philosopher David Hume (1711-1776) argued that we can never establish causality based on temporal relationships.

Law: general scientific principles used to explain and predict events across all situations (Laws of Thermodynamics).

Measurement: systematically assigning numbers (representing frequency, quality, quantity, or size) to an event.

Methodology: scientific procedures used to collect and analyze experimental data.

Necessary cause and effect relationship: The antecedent condition (IV) is required to produce a change in the dependent variable. For example, gas is required to run your automobile.

Necessary and sufficient cause and effect relationship: the first or primary cause of a phenomenon, which means an explanation at the level of quarks and gluons.

Observation: systematic detecting and recording of events.

Principle of parsimony: good thinking includes a preference for the simplest explanation supported by the evidence (also called Occam's Razor).

Psychology experiment: a controlled procedure in which at least two different treatment conditions are applied to subjects whose behaviors are then measured and compared to test a hypothesis about the effects of the treatments on behavior.

Replication: repeating research studies to confirm prior findings. The replication may be exact (methodology is repeated precisely) or systematic (methodology is intentionally modified to generalize findings).

Science: the systematic gathering of data to provide descriptions of events taking place under specific conditions, enabling researchers to explain, predict, and control events.

Scientific method: steps scientists take to gather and verify information, answer questions, explain relationships, and communicate findings.

Subject: the scientific term for an individual who participates in research.

Sufficient cause and effect relationship: the antecedent condition is one of several ways to change the dependent variable. For example, weight loss can be produced by exercise or reducing fat intake.

Temporal relationship: an event occurs before another. The fact that A precedes B is insufficient to prove that A caused B.

Testable: ethical procedures exist for systematically manipulating antecedent conditions and measuring the outcome to test a hypothesis.

Theory: set of general principles used to explain and predict phenomena (Equity Theory).

Treatment: set of antecedent conditions (independent variable) created by the experimenter to affect subject behavior on the dependent variable.

Whitehead: Alfred North Whitehead argued the universe has an internal order that may be discovered using the scientific method.

Woodenheadedness: "Assessing a situation in terms of preconceived notions while ignoring or rejecting any contrary signs."

Group 1: (a) What is commonsense psychology? (b) Provide an everyday example. (c) Provide examples of nonscientific sources of data. (d) Why are these sources a problem for scientists? (e) Summarize the findings of the North, Hargreaves, and McKendrick (1999) study.

Group 2: (a) Explain the point of Box 1-1 on "When Court Decisions Substitute for Scientific Data." (b) Summarize Box 1-2 on "The Power of Negative Thinking." (c) Explain nonscientific inference. (d) How does the concept of the gambler's fallacy illustrate this problem? (e) How does nonscientific inference affect the way we perceive people?   
       
Group 3: (a) What did Alfred North Whitehead mean by the "scientific mentality?" (b) Why is this assumption essential to science? (c) What makes data empirical? (d) How was empirical data collection (Galileo) superior to commonsense data collection (Aristotle) when describing falling objects? (e) Which counterintuitive finding did Galileo discover?

Group 4: (a) What is a law? (b) What is a theory? (c) Explain the difference between laws and theories. (d) How did Sir Karl Popper believe that science advances? (e) Explain Schlegel's caution about theory-based expectancies?

Group 5: (a) What is good thinking, which is critical to the scientific method? (b) What is woodenheaded thinking? (c) What is parsimony? (d) How did Lewis apply parsimony to developmental findings involving infants? (e)

This chapter examines both the content and process of science. The authors demonstrate the need for scientific methodology by examining the limitations of commonsense psychology, which utilizes nonscientific sources of data and inference. They explain how modern science avoids the errors inherent in commonsense psychology by assuming a natural order (the scientific mentality), gathering observable data, developing laws or theories to organize and explain our findings, good thinking (objective, organized, rational, and parsimonious reasoning), challenging findings through attempts to falsify new hypotheses (self-correction), publicizing results, and repeating experimental procedures to confirm previous findings (replication).

Next, the chapter describes the tools of psychological science. These include observation, measurement, and experimentation. The authors introduce the concept of antecedent conditions, explain how researchers manipulate antecedents in a psychology experiment, and define the minimum requirements for an experiment (we must have procedures for manipulating the setting and the predicted outcome must be observable). They define a psychology experiment as a controlled procedure in which we apply at least two different treatment conditions to subjects and then measure and compare subject behaviors to test an experimental hypothesis. Finally, they explore the problem of inferring a cause and effect relationship between treatment conditions and subjects’ behavior. They describe spatial and temporal causal relationships, discuss both necessary and sufficient conditions under which events will occur, and conclude that psychologists mainly study sufficient, temporal cause and effect relationships.

The chapter concludes with an overview of the text’s organization into four major parts: Introduction, Method, Results, and Discussion. This division parallels how scientists conduct experiments and the sections of a research report.


The need for scientific methodology

Scientia means knowledge (data and methodology). Heider called nonscientific data gathering commonsense psychology. This approach uses nonscientific sources of data and nonscientific inference. Nonscientific sources of data include statements from attractive sources that we accept without critical thinking. Further, we are often unaware of our own decision-making processes. We also draw nonscientific inferences from data. Examples include overuse of trait explanations for others' behavior, stereotyping (describing people based on the belief that specific behaviors cluster together), the gambler's fallacy (failure to estimate the actual probabilities of events), and overconfidence bias (feeling more confident about our conclusions than is warranted).

The characteristics of modern science

Alfred North Whitehead’s scientific mentality assumes that behavior follows a natural order and can be predicted. Science systematically gathers empirical data (data observed or experienced). Science seeks general principles like theories and laws.

A theory is an interim explanation: a set of related statements used explain and predict phenomena. Sir Karl Popper argued that science progresses through progressively better theories. Theories create dangerous expectancies concerning what is worth studying and of experimental outcomes.

A law consists of statements generally expressed as equations with few variables that have overwhelming empirical support. Laws, like the Laws of Thermodynamics, are useful in the physical sciences.

The scientific method uses good thinking. Data collection and interpretation are systematic, objective, and rational. The principle of parsimony (simplest explanation is preferred) is used. Science is self-correcting. Popper argued that we should attempt to falsify theories by testing the hypotheses (if-then statements) that follow from them. Scientists publish results to exchange information and avoid wasted effort. Replication (exact or systematic repetition of a study) increases confidence in experimental results.

The tools of psychological science

Observation is systematic data gathering. Measurement is assigning numerical values or labels to objects, events, or their characteristics. Experimentation is manipulation of an independent variable and measurement of the effect on the dependent variable.

Predictions must be testable. This means that we must be able to manipulate the setting, the process must be objective (unbiased), and the manipulation must be ethical.

Scientific explanation in psychological science

Explanation requires specifying the antecedent condition, which are the circumstances that come before the behavior. Treatments are sets of antecedent conditions we create to influence research participants. A psychology experiment applies at least two different treatment conditions to subjects under controlled conditions. An experiment helps us to determine a temporal cause and effect relationship between the treatment conditions and behavior changes. The IVs come before the change in the DVs. Hume argued against this approach.

Experiments allow us to find sufficient causes for the events we observe. A necessary cause is a condition required to produce a result (a snowmobile needs fuel to run). A sufficient cause is one of several conditions that could produce a result (exercise can reduce weight).