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Chapter 1-4

CHAPS 1-4 from 3RD EDITION

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Department
Psychology
Course
PSY280H1
Professor
Matthias Niemeier
Semester
Fall

Description
CHAPTER 1 INTRODUCTION Sensation and PerceptionAbility to detect the pressure of a finger and perhaps to turn that detection into a private experience is an example of sensationPerception can be thought of as the act of giving meaning to those detected sensationsFrench philosopher Etienne Bonnot de Condillacasked his readers to imagine mental life of a statue with no senses and concluded that the statue would have no mental life with more senses and more experience Condillac imagined a real mental life developing in statue THRESHOLDS AND THE DAWN OF PSYCHOPHYSICSGustav Fechner invented psychophysics and is thought to be the true founder of experimental psychology even if that title is usually given to Wilhem Wundt who began his work a little later Fechner had a degree in medicine then turned from biology to physics and mathFechner suffered eye damage from gazing at the sun too much while performing vision experiments this led to his depression leaving him alone most of the time with his own thoughtsWhen his vision recovered he became absorbed with the relationship between mind and matterThis pursuit placed him in the middle of a classic philosophical debate between adherents of dualism and materialismDualism the idea that the mind has an existence separate from the material world of the bodyMaterialism the idea that the only thing that exists is matter and that all things including the mind and consciousness are the results of interactions between nits of matterFechner suggested panpsychism the idea that the mind exists as a property of all matterthat is that all matter has consciousnessFechner described his philosophy of panpsychism in his book called Concerning the Mental Life of PlantsFechners goal was to formally describe the relation between sensation mind and the energy matter that gave rise to that sensationHe called his theory psychophysics the science of defining quantitative relationships between physical and psychological eventsFechner was inspired by the findings of Ernst WeberWeber used a device to measure the smallest distance between two points that was required for a person to feel two points instead of oneTwopoint touch threshold the minimum distance at which two stimuli are just perceptible as separateWeber also discovered the just noticeable difference JNDJND the smallest detectable difference between two stimuli or the minimum change in a stimulus that enables it to be correctly judged as different from a reference stimulusThe smallest weight that could be detected was always close to onefortieth of the standard weightWeber fraction the constant proportionality in Webers lawWebers law the principle describing the relationship between stimulus and resulting sensation that says the just noticeable difference is a constant fraction of the comparison stimulusFechners law a principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation increases proportionally to the logarithm of the stimulus intensity o Sk log RS is the psychological sensation which is equal to the logarithm of the physical stimulus level log R multiplied by a constant kAbsolute threshold the minimum amount of stimulation necessary for a person to detect a stimulus 50 of the time Psychophysical MethodsMethod of constant stimuli a psychophysical method in which many stimulus ranging from rarely to almost always perceivable are presented one at a time Participants respond to each presentation yesno samedifferent and so onMethod of constant stimuli can be somewhat inefficient in an experiment because much of the subjects time can be spent with stimuli that are clearly well above or below thresholdMethod of limits a psychophysical method in which the particular dimension of a stimulus or the difference between two stimuli is varied incrementally until the participant responds differently o There is some overshoot in judgements meaning it takes more intensity to report hearing the tone when its increasing and more decreases in intensity before a listener reports the tone cannot be heardMethod of adjustment a method of limits in which the subject controls the change in the stimulus o This method is not usually used to measure thresholds Scaling Methods and SuperstarsMagnitude estimation a psychophysical method in which the participant assigns values according to perceived magnitudes of the stimuli o Works well when observers are free to choose their own range of numbers o Magnitude estimation invented by Harvard psychologist S S StevensStevens power law a principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation is proportional to the stimulus magnitude raised to an exponent o SaIbWebers law involves clear objective measurementFechners law begins with the same sort of objective measurements and Webers but the law is actually a calculation based on some assumptions about how sensation works in particular Fechners law assumes that all JNDs are equivalent in fact this turns out to be incorrect and leads to some places where the law is violatedStevens power law describes rating data quite well but notice that rating data are qualitatively different from the data that supported Webers lawCrossmodality matching the ability to match the intensities of sensations that come from different sensory modalitiesThis ability enables insight into sensory differences For example a listen might adjust the brightness of a light until it matches the loudness of a toneThere is a molecule called propylthiouracil PROP that some ppl experience as very bitter while others experience it as almost tasteless this is a limitation to crossmodality matchingSupertasters an individual whose perception of taste sensations is most intense Signal Detection TheorySignal detection theory a psychophysical theory that quantifies the response of an observer to the presentation of a signal in the presence of noise Measures obtained from a series of presentations are sensitivity d and criterion of the observer o Posits that the stimulus youre trying to detect is always being detected in the presence of noise or internal noiseInternal noisestatic in your nervous systemExternal noisegenerated in the worldCriterion in SDT an internal threshold that is set by the observer If the internal response is above criterion the observer gives one response eg yes I hear that Below criterion the observer gives another response eg no I hear nothing
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