1. The Enligtenment
Since the Renaissance, Europe undergoes a gradual change from depending on authority as the source of truth to relying on scientific methodology.
In full swing by the late 1700s.
The American Revolution

2. The Imperfect Human Observer
Locke and Berkeley
Perception is subjective, not objective
Cannot assume a one-to-one correspondence between the nature of the physical object and our perception of it
Scientists began to focus on the physiological processes involved in sensing and perceiving

3. Physiology of the Nervous System
Luigi Galvani ( )
Italian Physiologist
Identified electricity as the “currency” of the nervous system
Nephew (Giovanni Aldini) continued the tradition using severed heads of criminals
More Showmanship than Science

4. The Electricity Craze

5. The Guillotine Problem
Theodor Bischoff
Smelling salts, “Pardon!”
No response
Concluded that bodily twitches were not conscious
Robert Whytt ( )
Extensive study of decapitated animals
Habit formation
Alluded to Classical Conditioning

6. Early Physiology Johannes Müller (1801-1858)
: Handbook of the Physiology of Mankind
Aimed to
Localize functions within the nervous system
Pinpoint peripheral sensory receptor mechanisms

7. Johannes Müller Doctrine of Specific Nerve Energies
The mind is directly aware not of objects in the physical world but of states of the nervous system.
“The qualities of the sensory nerves of which the mind receives knowledge in sensation are specific to the various senses, the nerve of vision being normally as insensible to sound as the nerve of audition is to light. “

8. Paul Broca (1824-1880) The Clinical Method (1861)
Broca’s area: the speech center in the 3rd frontal convolution of the left hemisphere of the cerebral cortex

9. Mapping from the Outside
Franz Josef Gall ( )
Used the clinical method to map the brain and confirm:
Existence of white and gray matter
Fibers from each brain side to the opposite spinal column side
Fibers connecting the two brain hemispheres
“How do the size and shape of the brain reveal information about brain facilities?”
Can it be mapped from the outside?

10. Phrenology J.G. Spurzheim (1776-1832) Gall’s student
Took specific nerve energies a little too far

11. Pierre Flourens (1794-1867) Prof. of Natural History-Paris
Used extirpation (ablation)
Isolate the parts
Remove, when necessary, the entire parts
Always prevent the complication of the effects on the lesions due to the effects of effusions.

12. Pierre Flourens (1794-1867) Six large functional areas of CNS
Cerebral cortex (perception, intelligence, will)
Cerebellum (coordination of movements)
Medulla oblongata (vital center)
Corpora quadrigemina (supports seeing)
Spinal cord (conduction)
Nerves (excitation)
Brain has GROSS specialization, but is probably an interdependent network

13. Gustav Fritsch and Eduard Hitzig (1870)
Electrical stimulation method: “A technique for exploring the cerebral cortex with weak electric current to observe motor responses.”
Stimulation of certain cortical areas results in motor responses such as leg movement

14. Gustav Fritsch and Eduard Hitzig (1870)
“A part of the convexity of the hemisphere of the brain of the dog is motor another part is not motor. The motor part, in general, is more in front, the non-motor part more behind. By electrical stimulation of the motor part, one obtains combined muscular contractions of the opposite side of the body. …such facts show that the origin of at least some function of the soul is bound up with circumscribed parts of the brain” - F&H, 1870
The cerebral hemispheres control voluntary movement

15. Gustav Fritsch and Eduard Hitzig (1870)

16. Physiology of the Nervous System
Camillo Golgi ( )
Italian neurologist
S. Ramón y Cajal ( )
Spanish neuroanatomist
Nobel Prize 1906

17. Cajal and Others Accepted as fact by the end of the 19th century:
Gross anatomy defines the direction of neural information (cell body >>>axon>>>synapse)
Neuron-Neuron Communication occurs at the synapse
Discovered the direction of travel for brain and spinal cord nerve impulses
Nerve fibers = bundles of discrete neurons separated by synapses
Supported the mechanistic view
Atomistic structures combined to produce complex complex structure

18. The Beginnings of Experimental Psychology
Four German physiologists directly responsible for initial applications of experimentation to mind:
Hermann von Helmholtz
Ernst Weber
Gustav Theodor Fechner
Wilhelm Wundt

19. Why Germany? German approach to science
Experimental physiology established and recognized to a unique degree
The German temperament: exactness and precision
Use of the inductive method
Ready acceptance of biology as a science
Broad definition of science

20. Germany
Results
Series of important discoveries in the sciences
German university professors directly responsible for growth and development of scientific psychology

21. Hermann von Helmholtz (1821–1894)
Born in Potsdam, Germany
Delicate health
1838: enrolled at a Berlin medical institute: free tuition to future army surgeons
Seven years in the army

22. Hermann von Helmholtz (1821 – 1894)
Invented the ophthalmoscope
: Handbook of Physiological Optics
1863: On the Sensations of Tone (research on acoustics)
Also wrote on a diversity of topics including hay fever, glaciers, geometry
Indirectly contributed to inventions of the wireless telegraph and radio

23. The contributions of von Helmholtz
First empirical measurement of the rate of conduction of the neural impulse (90 ft/sec)
Suggested thought and movement are successive, not simultaneous
Reaction times for sensory nerves in humans
Studied mechanism by which internal eye muscles focus the lens
Revised and extended a theory (Young-Helmholtz) of color vision that correctly predicted three types of cones

24. Ernst Weber (1795 – 1878) Born in Wittenberg, Germany
1815: PhD at university of Leipzig
1817 – 1871: taught anatomy and physiology at Leipzig
Primary research interest: physiology of sense organs
Applied experimental methods to problems of psychology
Explored new fields: cutaneous sensations rather than just vision and hearing

25. Ernst Weber (1795 – 1878) Thresholds
Two-point discrimination of the skin
Predicted layout of sensory cortex

26. Ernst Weber (1795 – 1878) Just noticeable differences (JND)
Discrimination depends on the relative difference between and not on the absolute weights of objects
Weber’s law: a constant ratio for each sense
Perception of a stimulus is not directly correlated to the physical stimulus

27. Ernst Weber (1795 – 1878) The Big Issues
Revealed a way to investigate the mind-body relationship
Demonstrated the utility of experimental methods as a means of studying psychological phenomena

28. Gustav Theodor Fechner (1801-1887)
Born in southeastern Germany
1817: began medical studies at University of Leipzig
Attended Weber’s lectures on physiology
Professor at Leipzig

29. Gustav Theodor Fechner (1801-1887)
Episode of Depression followed by euphoria and delusions of grandeur
Developed the idea of the pleasure principle
Concept later influenced Freud
1844: officially an invalid, given a pension by university of Leipzig
Remained at Leipzig in excellent health with continuing important scientific contributions until his death at 86

30. Quantifying Mind and Body
1850: While lying in bed had insight about the law governing the mind-body connection
A quantitative relationship between a mental sensation and a material stimulus
Effects of stimulus intensities are relative to the amount of sensation that already exists
Fechner crossed the barrier between body [physical stimulation] and mind [mental sensation] by relating one to the other empirically, making it possible to conduct experiments on the mind.

31. Gustav Theodor Fechner (1801-1887)
Proposed two ways to measure sensation
Absolute threshold: “the point of sensitivity below which no sensations can be detected and above which sensations can be experienced.”
Only the lowest level of a sensation can be determined using method of absolute threshold
Presence or absence of a stimulus

32. Weber’s (Fechner’s) Law: S = K log R
Difference Threshold
For each sense, “there is a certain relative increase in stimulus intensity that always produces an observable change in the intensity of the sensation.”
S: magnitude of the sensation [the mind or mental quality]
K: a constant
R: magnitude of the stimulus [the body or material (physical) quality]
Log: logarithmic relationship

33. Psychophysics
Psychophysics: “the scientific study of the relations between stimulus and perception”
Method of average error (method of adjustment)
Over a number of trials, subject adjusts a variable stimulus until it is perceived to be equal to a standard stimulus
The average of the obtained differences = error of observation
Used to measure reaction time and visual and auditory discriminations
Calculating the mean is basically drawing on the method of average error

34. Psychophysics Method of Constant Stimuli
Uses two constant stimuli: a standard weight and a comparison weight
Goal is to measure the stimulus difference required to produce a judgment of the second weight as heavier, lighter, or equal to the first weight
Method of Limits (differential threshold)
Two stimuli such as weights presented to the subjects
Experimenter increases or decreases one stimulus until subject detects a difference
Many trials are used, and jnds are averaged

35. In brief, Fechner
Countered the notion that psychology could never be a science because psychological processes not measurable
Provided the prerequisites for a science of psychology by making it possible to measure mental experience
Provoked Wundt’s plan for an experimental psychology
Gave psychology precise and elegant techniques of measurement

36. By the mid 19th century natural science methods were being used to study mental phenomena
British empiricists outlined the importance of understanding the limitations of the senses
German physiologists described functioning of the senses and paved the way for Wilhelm Wundt who brought them together by founding psychology