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Chapter 5

chapter 5


Department
Psychology
Course Code
PSYA01H3
Professor
Steve Joordens
Chapter
5

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Psychology Chapter 5:
Sensation
-Everything we learn is detected by sense organs and transmitted to our brains by
sensory nerves
-Provides useful information about external world
-Milner and Goodale: Vision evolved to provide distal sensory control of movements
that the animals make in order to survive and reproduce
-Audition is extremely important for our social behaviour
-Vision: provides info about distant events, as with smell, tells us about sources of
aromatic molecules far upwind
Sensory Processing:
-Sensation: detection of elementary properties of a stimulus, ex. warmth, color
-Perception: detection of the move complex properties of a stimulus, including its
location and nature; involves learning,
-Ex. seeing color red is a sensation and seeing a red apple is perception
-Pure sensation involves “prewiredphysiological mechanisms
Transduction:
-Sense organs: detect stimuli provided by light, sound, odour, taste, or mechanical
contact with environment
-this info is transmitted to brain by neural impulses (action potential)
-Task of the brain is to analyze info and reconstruct
-Transduction: conversion of physical stimuli into changes in the activity of receptor
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cells of sensory organs
-Receptor Cells: neuron that directly responds to a physical stimulus, such as light,
vibrations, or aromatic molecules
Sensory Coding:
-Code = system of symbols or signals representing info
-Have two forms: anatomical coding and temporal coding
-Anatomical Coding: means by which the nervous system represents information;
different features are coded by the activity of different neurons
-Temporal Coding: means by which the nervous system represents information;
different features are coded by the pattern of activity of neurons
-simplest form = rate (how intense it is)
Psychophysics:
-Psychophysics: branch of psychology that measures the quantitative relation between
physical stimuli and perceptual experience
-Weber: investigated ability of humans to discriminate between various stimuli
-Just-noticeable difference (jnd) = smallest change in magnitude of stimuli that c person
can detect
-Weber fraction: ratio between jnd and the magnitude of a stimulus; reasonably
constant over the middle range of most stimulus intensities
-Fechner: used Webers concept to measure peoples sensations and showed how a
logarithmic function could be derived from Webers principal
-Norwich and Wong: provided a technical overview of how these perspectives relate to
each other
-S.S. Stevens: came up with the formula: S = kIb (exponential b)
-S = psychological magnitude of sensation
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-I = intensity of physical stimulus
-Threshold: point at which a stimulus, or a change in the value of a stimulus can just be
detected
-Difference Threshold: An alternative name for jnd
-Absolute Threshold: minimum value of a stimulus that can be detected
-Signal Detection Theory: mathematical theory of the detection of stimuli, which
involves discriminating a signal from the noise in which it is embedded and which takes
into account participants willingness to report detecting the signal
-Receiver Operating Characteristic Curve (ROC curve): graph of hits and false
alarms of participants under different motivational conditions; indicates peoples ability
to detect a particular stimulus
Vision:
Light:
-consists of radiant energy (similar to radio waves)
-Wavelength: distance between adjacent waves of radiant energy; in vision, most
closely associated with the perceptual dimension of hue
-electromagnetic spectrum = part our eyes can detect
-visible spectrum = part we see as light
The Eye and its Functions:
-Cornea: transparent tissue covering the front of the eye
-Sclera: tough outer layer of the eye; the “whit of the eye
-Iris: pigmented muscle of the eye that controls the size of the pupil
-glaucoma: aqueous humour is produced too quickly or if passage that returns it to the
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