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Experimental Psychology PSY 433. Appendix A – Experimental Psychology: A Historical Sketch. Origins in Philosophy. Mind-body problem – are the mind and body the same or different? If they are different substances, how do they interact or communicate?

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experimental psychology psy 433

Experimental PsychologyPSY 433

Appendix A – Experimental Psychology: A Historical Sketch

origins in philosophy
Origins in Philosophy
  • Mind-body problem – are the mind and body the same or different?
  • If they are different substances, how do they interact or communicate?
    • Dualism – mind (soul) is not governed by physical laws but possesses free will.
    • Descartes – mutual interaction.
    • Animals do not possess souls and can be studied because they are physical.
physiology changed philosophy
Physiology Changed Philosophy
  • Localization of cerebral function by physiologists showed that the brain is the organ of the mind.
  • Mental states were shown to affect the body.
    • Trauma, mesmeric trance, mental suggestion.
  • Huxley’s “Epiphenomenalism” – mental states have no causal efficacy, like paint on a stone (neurophysiology is the stone, mind is the paint).
british empiricism
British Empiricism
  • Locke, Berkeley, Hume, Hartley
  • Mind may follow laws and thus be modeled just as the physical world is.
    • Elements (ideas)
    • Forces (associations between ideas)
  • Tabula rasa – mind is a blank slate written upon by experience.
  • Mental activity may be mechanical:
    • Mind as a machine
application of scientific method
Application of Scientific Method
  • Philosophy uses different methods than psychology:
    • Anecdote, reflection, logic
  • Experimental psychology emerged out of the study of sensation, applying laws of physics and chemistry.
    • Now called psychophysics
  • “Application of scientific method to the problem of mind” created experimental psych.
helmholtz 1821 1894
Helmholtz (1821-1894)
  • Used experimental methods to study vision and audition.
  • Reaction times were used to determine the speed of neural impulses.
    • Test response-times for stimuli from the shoulder and from the ankle.
    • Nerve impulses are slow – 50 meters per sec.
  • Reaction times vary considerably across individuals and across trials – how is precise measurement possible?
weber 1795 1878
Weber (1795-1878)
  • Weber studied perceptions of weight and tried to relate these to actual physical weight.
    • Weight is an objective physical property of objects.
  • The greater the weight, the greater the difference between it and a heavier weight must be in order to be detectable.
  • Weber’s Law -- Just-noticeable difference (JND) is a constant across a sensory modality.
just noticeable difference jnd
Just Noticeable Difference (JND)
  • How much must a stimulus change in order for a person to sense the change.
    • This amount is called the just noticeable difference (JND)
    • The actual size of the JND aries with the size of the weights being compared.
  • JND can be expressed as a ratio:

where R is stimulus magnitude and k is a constant and DR means the change in R (D usually means change in science)

fechner 1801 1887
Fechner (1801-1887)
  • Tried to relate physical properties to psychological sensations:
    • Related the objective to the subjective.
  • Fechner’s Law – each JND corresponds to one subjective unit of measure on a rating scale
    • This relationship can be described mathematically.
  • Credited with founding psychophysics.
fechner s law
Fechner’s Law
  • Fechner called Weber’s finding about the JND “Weber’s Law.”
  • Fechner’s formula describes how the subjective sensation is related to increases in stimulus size:

where S is sensation, k is Weber’s constant and R is the magnitude of a stimulus

  • He also used catch trials to study guessing.
relationship of jnd to stimulus
Relationship of JND to Stimulus

S.S. Stevens modified Fechner’s Log Law to a Power Function in the early 1950’s.

wundt ebbinghaus
Wundt & Ebbinghaus
  • Wundt (1832-1920) organized psychology and helped to establish it as an independent discipline.
    • Wrote “Principles of Physiological Psychology”
    • Did not believe higher mental processes (memory, thought, creativity) could be studied experimentally.
  • Ebbinghaus (1850-1909) demonstrated that memory could be studied experimentally.
stucturalism vs functionalism
Stucturalism vs Functionalism
  • Structuralism – focused on the contents of mind.
    • Sensations, images (ideas), affections
    • Used introspection to identify basic elements.
    • Introspection proved to be an unreliable method.
  • Functionalism – focused on the adaptive function of psychological processes within a context.
    • Not much experimental work done.
  • Rejected structuralism and functionalism.
    • Both referred to mentalistic contents of mind that could not be directly observed.
  • Emphasized focus on relating behavior to evoking stimuli and contexts.
  • Radical behaviorists:
    • Watson
    • Skinner
  • Now nearly all experimental psychologists are behaviorists to some extent.
gestalt psychology
Gestalt Psychology
  • Reaction against structuralism.
  • Whole is greater than the sum of its parts.
    • Complex mental phenomena cannot be understood by examining elements.
  • Wertheimer’s demonstration of shape constancy seemed incompatible with structuralism.
  • Influential in cognitive psychology.
the cognitive revolution 1950 present
The Cognitive Revolution (1950-present)
  • Using scientific methods to study mental processes that are linked to observable behaviors
  • The mind actively acquires information, and stores, retrieves, and uses knowledge
  • Influenced by the computer analogy and information processing theory.
cognitive neuroscience
Cognitive Neuroscience
  • Psychophysiology – intersection between psychology and physiology.
  • Neuroscientists team with psychologists using imaging techniques (PET, fMRI) to study cognitive activity.
    • Such results must be interpreted with caution
    • Observing that activity is occurring does not necessarily tell you what kind of activity is happening.
  • Today psychologists tend to identify more with areas of interest than with schools of thought (behaviorism, gestalt).
    • Specialization is the mark of a maturing science.
  • Experimental psychology is one of 54 divisions in the APA (Division 3).
  • Other societies: Psychonomic Society, APS, Society for Cognitive Neuroscience, society for Research in Child Development (SRCD).