Experimental Psychology and the Scientifc Method (lesson 2)

Hermann Ebbinghaus

"Psychology has a long past, but only a short history."

The Philosophical Origins of Psychology

The earliest discussions of psychological concepts can be traced back to ancient philosophy.
Philosophers such as Aristotle, Plato, and Descartes explored questions about the nature of the mind, perception, memory, and human behavior.

Mind-body problem

whether the mind and body are separate or the same in nature.

Dualism

once-popular belief

delayed the development of psychology as a science.

Early dualists believed the mind controls the body, but the body has little influence on the mind.

body

operates under physical laws, like inanimate objects.

mind

is not governed by physical laws because it possesses free will.

René Descartes and the Shift Toward Interactionism

René Descartes (1596–1650) challenged strict dualism by proposing mutual interaction:

The body can influence the mind.

The mind can influence the body.
Although Descartes still viewed the mind as immortal and possessing free will, he:

Encouraged studying the body as a mechanical system using scientific methods.
Argued that animals (which lacked souls) could also be studied scientifically.

Impact: Opened the door for applying the scientific method to organic systems, including human physiology.

British Empiricism and the Mechanistic View of the Mind

British empiricists (Locke, Berkeley, Hume, Hartley) were influenced by mechanistic models used in astronomy and physics.
They proposed that:

The mind consists of elements (ideas).
These elements interact through forces (associations), which follow lawful principles. Mental processes operate mechanically, similar to physical systems.

Associationism

belief that thoughts and perceptions are governed by laws of association based on sensory experiences.

John Locke’s "Tabula Rasa" (Blank Slate) Theory:

Locke described the mind as a blank slate at birth.

He argued that all knowledge comes from experience:

While philosophers laid the theoretical groundwork for psychology, their methods were:

• Anecdotal

• Reflective (introspective)
  

  These methods advanced philosophical thought but did not significantly advance scientific knowledge.

Breakthrough moment:

The application of the experimental method to studying the mind and behavior.

Edwin G. Boring described this shift as:

“The application of the experimental method to the problem of mind is the great outstanding event to which no other is comparable.”

Sensory Physiology

Mid-19th-century German physiologists studied

Sensory physiology examines:

The structure and function of sense organs (eyes, ears, etc.).
How sensory information is transmitted to the brain via the nervous system.

Hermann von Helmholtz

was primarily a physicist and physiologist rather than a psychologist.
He did not aim to establish psychology as an independent field, but his research had a significant impact on its development.
His work mainly focused on vision and audition (hearing), contributing greatly to sensory physiology.
He conducted pioneering experiments that bridged the gap between physiology and experimental psychology.

Ernst Weber

an anatomist and physiologist whose research primarily focused on cutaneous sensation—the sense of touch. His work laid the foundation for the study of sensory perception.

Just Noticeable Difference (JND)

Weber discovered that the ability to detect differences in weight depends on the magnitude of the standard weight.

When a weight is small, only a small difference is needed to notice a change.

When a weight is large, a greater difference is required for detection.

Ernst Weber (1795–1878): The Foundations of Sensory Psychology

Weber’s Law

He found that the ratio of the difference required for a just noticeable difference (JND) to the original stimulus is a constant for each sense.

This discovery formed the basis of modern psychophysics, influencing how we study perception today.

Gustav Fechner

expanded upon Weber’s discoveries and established Psychophysics, the study of how physical stimuli are translated into psychological experiences.

Psychophysics

Fechner aimed to find quantitative relationships between physical stimuli and perception.

Fechner’s Law:

He extended Weber’s Law, proposing a mathematical formula to describe how perceived intensity increases as stimulus intensity grows.

This principle explains why a small increase in brightness is noticeable in a dimly lit room but barely detectable in daylight.

Wilhelm Wundt (1832–1920): The Father of

Experimental Psychology

is often regarded as the founder of psychology as an experimental discipline.

First Psychology Laboratory (1879, Leipzig, Germany):

This lab marked the official beginning of psychology

as a science.

Principles of Physiological Psychology (1874):

A systematic review of psychological knowledge, laying the foundation for experimental methods in psychology.

Introspection

Wundt used a method where trained participants analyzed their own conscious experiences in response to stimuli

Experimental Psychology

studying sensation and perception.

Higher Mental Processes

(e.g., memory, thought, creativity), which he believed could not be studied experimentally but rather through historical and cultural analysis.

Hermann Ebbinghaus (1850–1909): The Science of

Memory

proved otherwise by pioneering the experimental study of memory.

First Systematic Experiments on Memory (1879):

Used himself as a subject, memorizing and recalling nonsense syllables to measure learning and forgetting.

Forgetting Curve:

• Demonstrated how memory fades over time in a predictable pattern.
  

• Most forgetting occurs immediately after learning, then slows over time.

Spacing Effect:

Showed that information is retained better when study sessions are spread out rather than crammed.

Antecedent conditions (antecedents):

circumstances that occur before an event or behavior that needs explanation.

Identifying all antecedents allows the prediction of behavior: If XYZ antecedents occur, a particular behavior is expected.

Necessary condition

Must be present for an event to occur.

Sufficient condition

Can produce an outcome but is not required for it.

Phrenology

reading skull bumps to determine personality

Physiognomy

judging personality based on facial features

Mesmerism

hypnotism-based healing

Spiritualism

contacting spirits for guidance