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Chapter 1

Chapter 1.docx

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Matthias Niemeier

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Chapter 1 Introduction – Early Philosophy of Perception  The Matrix was inspired by “Allegory of Cave” in Plato’s “Republic  Plato compares our ordinary sense of reality to that of prisoners in cave o Describes prisoners tethered together since childhood, able to see only wall in front of them o Behind is a fire, and between fire and backs of prisoners are men, sometimes talking and sometimes not, carrying statues and other objects o Paints imaginary picture to emphasize how critically conception of reality depends on what we can learn about world through our senses  Perception and sense of reality are products of evolution  Senses evolved to match just the sorts of energy in environment that are most important for survival  Heraclitus – best known for famous statement “you can never step into the same river twice” o Used metaphor to stress view that everything is always changing o No 2 experiences can ever be identical, because experiencing first event changes way we experience same event a second time  7 facts follow from Heraclitus’ simple observation o Perception doesn’t depend only on energy and events that change in the world o Perception depends on qualities of perceiver o Experience with world around us plays large role in way perception works – begins early in life  Perceptual systems are acutely sensitive to change many ways, every sense highlights and emphasizes changes  Adaptation: reduction in response caused by prior or continuing stimulation o Render things that are steady or predictable in environment much less salient than things that change  Democritus – had almost complete trust in senses o Trust arose from radical idea that world is made up of atoms that collide o Believed that sensations are caused by atoms leaving objects and making contact with our sense organs o Senses should be trusted because perception is result of physical interaction between world and bodies o Most reliable senses were those that detect weight or texture of objects o Held that all other qualities were secondary because they have to involve atoms moving from object to interact with atoms of perceiver o Wrong – usually light reflected from an object that allows us to see object – no atomic films peeling off of visible objects o Made distinction between primary qualities (directly perceived – weight, texture) and secondary qualities (require interaction between atoms from objects and atoms in perceiver)  Sensation: concerned with ways info from world is picked up by sense organs and detected by owners  Sensory transducers: any substance or structure that changes energy from one form to another. For every sense, transducers transform info into neutral signals that can be interpreted by brain  Perception: interpretation of signals. Likely to depend more on experience than sensory reception does Nativism and Empiricism Nativism  Plato believed mind and body are separate entities and that certain mental abilities must be innate  Nativism: idea that mind produces ideas that aren’t derived from external sources – have abilities that are innate and not learned  Rene Descartes came to similar conclusion concerning relationship between mind and body and argued that only humans have mind o Mind is unextended (doesn’t take up space) and has no substance o Thought true ideas must come from mind and didn’t trust senses o Asserts  Dualist: idea that mind and body both exist  Paul Bloom believes children come into world ready to hold dualist belief that humans have both material bodies and immaterial minds  Monism: idea that mind and matter are formed from, or reducible to single ultimate substance or principle of being  Materialism: idea that physical matter is only reality, and everything including mind can be explained in terms of matter and physical phenomena. Type of monism  Mentalism: idea that mind is true reality and objects exist only as aspects of mind’s awareness. Type of monism  Mind body dualism: idea positing existence of 2 distinct principles of being in universe Empiricism  Thomas Hobbes concluded that only sensible answer is that o Rejected concept of spirit or God, because things would have no matter in bodies o Rejected nativist ideas o Wrote that imagination “is nothing but decaying sense”  Empiricism: idea that experience from senses is only source of knowledge  Hobbes viewed all mental activity as consequence of experience o Thought memories were sensory experiences that were old and faded  John Locke provided empiricism’s most vivid image – newborn mind as tabula rasa (blank slate) o Suggested that ideas must be created through experience o Believed experiences and ideas began when simple stimulation of sense organs is conveyed to mind  George Berkeley o Argued that no single strategy will always tell us how distant something is; must use several visual cues to perceive distance o Concluded that we learn how to perceive distance by experiencing objects and scenes in world o Concluded that all knowledge about world must come experience  David Hume o Reliability: consistency of measurements o Validity: relationship of measurement to what is measured o Argued that world seems very real because perception is reliable o Perceptual illusions are instances in which perception can be very reliable but not accurate representation of world Dawn of Psychophysics  Gustav Fechner o Sometimes considered true founder of experimental psych o Wanted both mind and matter to exist, but knew problems with being dualist o Panpsychism: idea that all matter has consciousness o Goal was to formally describe relationship between sensation (mind) and energy (matter) o Psychophysics: science of defining quantitative relationships between physical and psychological (subjective) events  Ernst Weber o Tested accuracy of sense of touch using device – could measure smallest distance between 2 points that was required for person to feel 2 points instead of 1 o 2 point touch threshold: minimum distance at which 2 stimuli are just perceptible as different o Most important findings involved judgments of lifted weights o Found that ability to detect difference between standard and comparison weights depended on weight of standard – when light, must better at detecting small difference o Just noticeable difference/difference threshold: smallest detectable difference between 1 stimuli or minimum change in stimulus that enables it to be correctly judged as different from reference. th o Smallest change in weight could be detected was close to 1/14 of standard weight o Weber fractions: constant of proportionality in Weber’s law o Weber’s law: principle that JND is a constant fraction of comparison stimulus.  Fechner found way to describe relationship between mind and matter – assumed that smallest detectable change in stimulus could be considered unit of mind because smallest bit of change that is perceived. S = k log R. S is psychological sensation which equals ogarithm of physical stimulus level (log R) multiplied by K o Equation describes fact that psychological experience of intensity of light, sound, etc. increases less quickly than actual physical stimulus increases  Absolute threshold: minimum amount of stimulation necessary for person to detected stimulus 50% of the time Psychophysical Methods  Method of constant stimuli: many stimuli ranging from rarely to almost always perceivable are presented one at a time. Participants respond to each presentation; “yes/no”, “same/different” and so on o Requires creating many stimuli with different intensities o In between, more likely to hear some tone intensities than not hear them and would hear other lower intensities on only a few presentations o Because of variability in nervous system, stimuli near threshold will be detected some of time and missed other times – function relating probability of detection with stimulus level will be more gradual and must settle for arbitrary definition of an absolute threshold o Can be inefficient because much of subject’s time can be spent with stimuli that are clearly above or below threshol
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