Experimental PSY 433

Appendix A – : A Historical Sketch Origins in Philosophy

-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 .  Descartes – mutual interaction.  Animals do not possess souls and can be studied because they are physical. Rene Descartes (1596-1650) 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

 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

 Philosophy uses different methods than psychology:  Anecdote, reflection, logic  Experimental psychology emerged out of the study of sensation, applying laws of and chemistry.  Now called  “Application of scientific method to the problem of mind” created experimental psych. 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 studied 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. Demo

 Weber’s law for sound  https://www.youtube.com/watch?v=wVhiezBy MSU Just Noticeable Difference (JND)

 How much must a change in order for a person to 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. DR  k  JND can be expressed as a ratio: R where R is stimulus magnitude and k is a constant and DR means the change in R (D usually means change in ) 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 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: S  k log R 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

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

 Wundt (1832-1920) organized psychology and helped to establish it as an independent discipline.  Wrote “Principles of ”  Did not believe higher mental processes (, , creativity) could be studied experimentally.  Ebbinghaus (1850-1909) demonstrated that memory could be studied experimentally. Stucturalism vs Functionalism

 Structuralism – focused on the contents of mind.  Sensations, images (ideas), affections  Used 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 are behaviorists to some extent.

 Reaction against structuralism.  Whole is greater than the sum of its parts.  mental phenomena cannot be understood by examining elements.  Wertheimer’s demonstration of shape constancy seemed incompatible with structuralism.  Influential in . 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

– 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. Specialization

 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 , society for in Child Development (SRCD).