Introduction to Experimental Psychology: Origins, Methodology, and Scope
Origins of Experimental Psychology: Philosophy
Dualism: According to this theory, the body is governed by physical laws, as are inanimate objects, but the mind is not governed by such laws because it possesses free will. This was a once-popular position that probably greatly hindered the development of scientific psychology.
To the dualist, it makes no sense to apply scientific methods to discover laws of mental life because such laws are believed to not exist.
Early dualists argued that although the mind could control the body, there was little influence in the opposite direction.
René Descartes (1596–1650): His influential philosophical writings helped weaken the belief that the body and mind do not interact.
Mutual Interaction: Descartes advanced the idea that the body could affect the mind, and the mind could affect the body.
Mechanical Systems: While the dualist position remained and the mind was still regarded as immortal and as possessing free will and a soul, the body could be studied as a mechanical system by rational, scientific means.
The Study of Animals: Since animals were regarded as not possessing souls, it was considered that they too could be studied by methods applied to inanimate objects of physical science.
This expanded the application of the scientific method beyond purely physical systems to the study of organic systems.
British Empiricism: Philosophers such as Locke, Berkeley, Hume, and Hartley believed that the human mind could be profitably studied to discover mental laws.
Modeling the Mind: They proposed that the mind could be modeled in terms of elements (ideas) and forces (associations) that act on those elements in lawful ways.
Mechanical Nature: They emphasized the mechanical nature of mental phenomena, including "laws" of association in thought and the physical basis of the perception of the external world.
The Mind as a Machine: For scientific study, the mind could be treated like a machine.
Rejection of Innate Ideas: The British empiricists rejected the notion that some ideas are innate or develop without information from the external world impinging on the senses, a concept argued by Descartes and expanded on by Immanuel Kant.
Etymology of Empiricism: The name comes from the Greek word empeiria, meaning experience.
Transitions to Psychology: While philosophers prepared the way by treating the mind as subject to natural laws, their method was limited to anecdote and reflection. Moving toward scientific psychology required the application of the experimental methods and logic of science, which entered psychology through physiology.
Origins of Experimental Psychology: Physiology
Sensory Physiology: This refers to the physiology of the sense organs and the transmission of information from these organs to the brain via the nervous system. German psychologists in the mid-nineteenth century focused heavily on this area.
Hermann von Helmholtz: A physicist and physiologist credited with conducting transition experiments between physiology and experimental psychology.
Reaction-Time Experiment: Used to study the speed of neural impulses. Helmholtz stimulated a nerve at two different distances from the brain and measured the time difference in responding.
Experimental Design: He stimulated blindfolded subjects on either the shoulder or the ankle and measured how fast they could react by pushing a lever. By measuring the distance the impulse traveled from the ankle vs. the shoulder, he estimated the speed of nervous impulses.
Calculated Speed: Helmholtz estimated the speed of nervous impulses at the relatively slow rate of .
Four Pioneers of Early Scientific Psychology:
Ernst Weber: Focused on cutaneous sensation (the sense of touch). In his experiments, blindfolded subjects compared a standard weight to a comparison weight to see if they could detect a difference.
Just-Noticeable Difference (JND): The difference necessary for detection of a change.
Findings: The greater the standard weight, the greater the difference between the standard and comparison must be before a subject notices.
Weber’s Law: For any of the senses, the ratio of the amount of difference necessary to produce a JND to the standard is a constant. This law relates physical stimulation increase to the JND.
Gustav Fechner: Developed Fechner's Law, which is an extension of Weber's Law. It states that all JNDs produce equal increments in sensation; each JND step on a psychological scale corresponds to a physical stimulus one difference threshold greater than the preceding stimulus.
Wilhelm Wundt: Trained in physiology and medicine (under Helmholtz). He was the first person to consider himself primarily a psychologist.
Principles of Physiological Psychology (1874): Wundt’s book systematically reviewed psychology at the time; historian Boring called it the most important book in experimental psychology history.
First Laboratory: Credited with establishing the first laboratory of experimental psychology in in Leipzig.
First Journal: Established Philosophische Studien (Philosophical Studies).
Hermann Ebbinghaus: Discredited Wundt's beliefs about the limits of the experimental method by initiating pioneering experiments on human learning and memory.
Memory (1885): His major book documenting these studies.
Scientific Explanation and Experimental Concepts
Identifying Antecedent Conditions: In science, explanation involves specifying the circumstances that come before an event or behavior.
Antecedents: If a set of conditions (XYZ) occurs, a particular behavior is expected to follow. If XYZ occurs again, the same outcome is expected.
Treatment Conditions: Specific sets of antecedent conditions created in a psychology experiment. Comparing different treatment conditions allows for systematic testing of explanations.
The Psychology Experiment: A controlled procedure applying at least two different treatment conditions to subjects.
Measurements: Subjects' behaviors are measured and compared to test a hypothesis about the effect of treatments.
Groups Consistency: Special techniques like random assignment are used to ensure subjects in different conditions are as similar as possible.
Principles of Control: Successful experimentation relies on control achieved by:
Random assignment of subjects.
Identical presentation of treatment conditions.
Keeping the environment, procedures, and instruments constant so treatment conditions are the only things that change.
Cause-and-Effect Relationship: Within an experiment, this can be inferred if a specific set of antecedents always leads to a particular behavior.
Temporal Relationship: A relationship where the cause (treatment) occurs before the effect (behavior).
Necessary and Sufficient Conditions: Scientists seek to identify conditions for events; scientific research commonly involves identifying sufficient conditions.
Induction vs. Deduction:
Induction: Reasoning that proceeds from particular data to a general theory.
Deduction: Reasoning from general theory to particular data (predicting data based on theory).
The Science of Psychology
Definitions:
Psychological Science: Research about psychological processes underlying behavior.
Science (Content): The facts known (e.g., facts from psychology or chemistry courses).
Science (Process): The systematic gathering of data, noting relationships, and offering explanations.
Methodology: Scientific techniques used to collect and evaluate psychological data.
Data: Facts and figures gathered in research studies.
Need for Scientific Methodology:
Commonsense Psychology: Everyday data gathering that shapes beliefs but is constrained by unreliable sources and imperfect inferential strategies.
Nonscientific Data Sources: Includes Confirmation Bias, where people overlook disconfirming instances and seek only confirmatory behavior.
Nonscientific Inferences:
Overestimating behavior consistency due to perceiving others by traits.
Stereotyping: Automatically assuming characteristics based on expectations.
Gambler’s Fallacy: The belief that an event (like a slot machine payoff) is overdue despite probabilities remaining constant.
Overconfidence Bias: The tendency to feel predictions are more correct than they actually are, often increasing with more data.
Scientific Mentality:
Behavior follows a natural order and is predictable.
Determinism: Specifiable causes for behavior that can be discovered through research.
Empirical Data: Data that are observable or experienced.
Structuring Knowledge:
Laws: Principles with the generality to apply to all situations.
Theory: An interim explanation organized to pull together diverse facts into a scheme. Major functions include organization and prediction.
Hypothesis: A testable prediction.
Good Thinking: An approach that is systematic, objective, and rational.
Parsimony: Seeking simplicity, precision, and clarity. The simplest explanation is preferred until ruled out by conflicting data.
Replication: Repeating research procedures to verify outcomes. This is a principal tool of the scientific method to ensure data gathering was objective.
Research Objectives, Types, and Tools
Four Major Objectives of Research:
Description: Systematic and unbiased account of observed behavior characteristics.
Prediction: Knowing in advance when behaviors occur based on their association with other conditions.
Explanation: Knowledge of the conditions that reliably reproduce a behavior.
Control: Applying learned information to effect change or improve behavior.
Research Categories:
Applied Research: Designed to solve real-world problems.
Basic Research: Designed to test theories or explain psychological phenomena.
Tools of the Scientific Method:
Observation: Systematic noting and recording of events. Only observable events can be studied scientifically.
Measurement: Assignment of numerical values to objects/events using standardized units according to conventional rules.
Experimentation: Undertaken to test hypotheses. Three minimum requirements for testable predictions:
Procedures for manipulating the setting.
The predicted outcome must be observable.
The outcome must be measurable.
Research Techniques
Naturalistic Observation: Describing naturally occurring events without intervention. Different from casual observation.
Validity Challenges:
Delimiting: Choosing which behaviors to observe out of a huge range.
Reactivity: Participants' unplanned reactions to being observed/the researcher.
Ethology: Study of naturally occurring behavior, often in the wild.
Ethogram: A complete inventory of species-specific behaviors (e.g., mating, grooming, eating).
Case Study: A specific type of naturalistic observation focusing on an individual unit.
Survey Research: Obtaining large amounts of information from many people, usually via random sampling.
Relational Research: Determining how two or more variables relate without manipulation.
Ex Post Facto Data: Data that are "after the fact."
Experiment: Systematic manipulation of environmental factors to observe the effect on behavior.