Important dates. PSY 3360 / CGS 3325 Historical Perspectives on Psychology Minds and Machines since Vitalism vs. Mechanism

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1 PSY 3360 / CGS 3325 Historical Perspectives on Psychology Minds and Machines since 1600 Dr. Peter Assmann Spring 2019 Important dates Feb 20 *** TODAY *** Term paper draft due by midnight Upload paper to E-Learning March 4 Midterm Exam Optional extra credit: Midterm review benefit Upload to E-Learning Hermann Ludwig Ferdinand von Helmholtz ( ) Vitalism vs. Mechanism Vitalism: living things share a vital force that cannot be explained by the physical sciences (Müller) Mechanism: same laws apply to living and non-living things (Helmholtz) Principle of conservation of energy Johannes Müller Helmholtz' theory of perception Perception = active, unconscious, automatic, logical processes Unconscious inference Role of learning and memory in transforming sensory information Experiments with distorted lenses Motion pictures succession of still images Railroad tracks are parallel but seem to converge in the distance Visual Perception Perceptual Adaptation The idea that when one s visual field is altered (e.g., when images are shifted to the left or right from their normal locations while wearing special glasses), one s brain adapts to new perceptions automatically and unconsciously. 1

2 Visual Perception Unconscious Inference According to Helmholtz, the idea that perceptual adaptation and other perceptual phenomena might result from a process in which there is an unconscious adoption of certain logical rules. Young-Helmholtz theory of color vision Newton (1672) wavelength Trichromatic theory: human color vision involves three color receptors (RGB) Color receptors (cones) in the retina Laws of color mixing Color blindness Munsell color system Hue: dominant wavelength Value: brightness Chroma: purity Color Vision Color Mixing The phenomenon studied by Maxwell and others, showing that varying mixtures of spectral light can produce the same color sensations as pure spectral colors. James Clerk Maxwell ( ) A Scottish scientist who studied color vision and who provided the most complete analysis of color mixing in Complementary Colors Pairs of spectral colors (e.g., red green and blue violet) that, when mixed together, create a sensation of white light indistinguishable from sunlight. Primary Colors The spectral colors red, green, and blue, which are the building blocks for all of the kinds of color sensation. Thomas Young ( ) An English scientist who, like Helmholtz, suggested that the retina contains three types of receptor cells necessary for color vision. Young Helmholtz Trichromatic Theory Idea proposed by Thomas Young and Hermann von Helmholtz suggesting that there are three types of receptor cells in the eyes, each one responding to a different spectral hue, making color vision possible. 2

3 Theory of hearing Pitch Perception Helmholtz proposed that the basilar membrane, housed within the cochlea of the inner ear, responds selectively to the different frequency components of sound waves. low frequencies Helmholtz proposed that the location (place) of maximum vibration along the basilar membrane determines the pitch we perceive. Intensity Sine wave Frequency high frequencies Complex sounds have many components; the activation produced by the lowest one (called the fundamental frequency) determines the pitch. Pitch Perception Intensity Complex wave Frequency Intensity Frequency analysis Sine wave Complex wave Intensity Frequency Frequency Problem of the missing fundamental Frequency (in cycles/sec, or Hz) Original Missing fundamental Helmholtz proposed that nonlinear interaction in the cochlea re-introduces the missing fundamental. (We now know this hypothesis was incorrect). History of neuroscience Relationship between mind and body Are the mind and body (brain) separate entities controlled by different principles (dualism) or are they integrated (monism)? 3

4 History of neuroscience Localization of function Relationship between psychological functions and specific structures in the brain and nervous system Are areas of the brain specialized for separate functions (localized) or does the brain operate as an undifferentiated whole (holistic view)? History of neuroscience Localization of function Descartes: the mind could not be localized in the brain because its structures were paired; how could consciousness occupy two places at the same time? History of neuroscience Early theories Plato ( BC) Aristotle ( BC) Galen ( AD) Mechanism of animal spirits (fluid energies) René Descartes ( ) Fluid (hydrodynamic) theory of transmission of animal spirits animal spirits responsible for the flow of sensory and motor information in the body Reflex theory Dualist view of mind and body with pineal gland as the control center Thomas Willis ( ) John Locke s teacher detailed brain anatomy gray matter & white matter Cerebral cortex has convolutions; blood vessels Anatomy of subcortical centers Emerging viewpoints 1. Higher cognitive functions are mediated by the central nervous system. 2. Sensation and perception can be measured and mapped out using methods developed in other branches of science. 3. Concept of a threshold, the minimum amount of energy needed to elicit a change in perception. 4. Elaboration of the laws of association. 4

5 19 th century developments Changing views on the relationship between mind and body Improved techniques for studying perception Developments in physiology 1. Distinction between sensory & motor nerves 2. Doctrine of specific nerve energies 19 th Century Neuroscience Sensory and motor nerves Bell & Magendie two distinct types of nerves: ventral roots of spinal cord contain motor nerves. dorsal roots contain sensory nerves. differentiation of function Vitalism vs. Mechanism Johannes Müller ( ) Vitalism: living things share a vital force that cannot be explained by the physical sciences (Müller) Mechanism: same laws apply to living and non-living things (Helmholtz) Johannes Müller Doctrine of specific nerve energies sensory nerves can be stimulated in different ways to produce the same characteristic energy resulting in the same sensation. Rejected theory of animal spirits; hypothesized that nerve impulses were electrical; hence, too rapid to be measurable. Helmholtz studies of nerve conduction Helmholtz studies of nerve conduction Nerve propogation time in humans Problem: how to separate nerve propogation speed from other factors? Telegraph machine metaphor 1. Signal travels through sensory nerves 2. Response travels through motor nerves to the muscles 3. Central nervous system processes of perceiving and willing Invented by Hipp in the 1860s Simple reaction time in humans: subjects pressed a button in response to tactile stimulus Compared reaction times at different body locations By subtracting one reaction time from another, he estimated that nerve impulses travel at ~ feet per second Nerve impulses travel about 2x as fast in humans as in frogs Mental processes take time; they can be measured. 5

6 ( ) Dutch physiologist 15 years after Helmholtz study, Donders measured simple reaction time to visual stimuli A B C D E Next Donders presented a series of stimuli and asked subjects to respond to only one, specified beforehand. The extra time provided a measure of the mental act of discrimination. Response Subtractive method: the time taken to discriminate the complex stimulus minus the time to discriminate the simple stimulus. Choice reaction time: several different stimuli are presented and the response to each one is different. A B C D E Stimulus: A B C D E Response Response: a b c d e Stimulus: The time required to make a choice is determined by subtracting both simple and discrimination reaction times from the choice reaction time. A B C D E Franz Gall ( ) Gall postulated that the cerebral cortex serves the highest level of brain function. Analyzed character traits and skulls of famous people and criminals. Generated a list of 27 faculties (including sex drive, maternal behavior, aggression, etc). Launched new science called phrenology. Response: a b c d e "mental chronometry" 6

7 Physiognomy and phrenology Phrenology: surface of the skull mirrors the exaggeration of functional areas in the cortex. Bumps on the skull are associated with faculties that are prominent in individuals. Gall s work foreshadows the idea of localization of function. Paul Flourens ( ) Critic of the phrenology movement Ablation studies of animals Brain lesion studies suggested to Flourens that the cerebral hemispheres function together as a single unit Launched debate over localization of function Pierre Paul Broca ( ) cranial damage and lesions as a means of studying localization of cerebral function in humans. In 1861 Broca presented a case study of a man with normal cognitive functions in all respects except that he no longer possessed the ability to speak (aphasia). When the patient died, Broca performed an autopsy and revealed a lesion in the middle part of the frontal lobe of the left hemisphere. Pierre Paul Broca ( ) Broca s area: frontal lobe of the left hemisphere Hemispheric lateralization of function language center? Pierre Paul Broca ( ) cranial damage and lesions as a means of studying localization of cerebral function in humans. In 1861 Broca presented a case study of a man with normal cognitive functions in all respects except that he no longer possessed the ability to speak (aphasia). When the patient died, Broca performed an autopsy and revealed a lesion in the middle part of the frontal lobe of the left hemisphere. 7

8 Carl Wernicke ( ) In 1874, Carl Wernicke described a different pattern of language breakdown with injury to the temporal lobe of the left hemisphere, which he described as sensory aphasia. Other developments in neuroscience Galvani (1780) discovered that a frog s leg would twitch when the inside and outside of the muscle were connected in series with two different metals. Emil du Bois-Reymond ( ) du Bois-Reymond discovered the action potential in 1848 An action potential (or nerve impulse) is a pulse-like wave of voltage that travels along the axon of a neuron. Other developments in neuroscience Fritsch and Hitzig (1870) showed that electrical stimulation of regions of the cortex in dogs produced specific responses of individual muscle groups (motor strip). Other developments in neuroscience Lashley ( ) coined the term equipotentiality to describe the capacity of an intact part of the brain to take over the (memory) functions of an damaged portion. Wilder Penfield ( ) famous neurosurgeon; leading authority on epilepsy Electrical stimulation of the cerebral cortex in awake patients (prior to surgery) could produce complex perceptions or motor actions homunculus (cartoon map of motor cortex) 8