Chapter 4: Sensation & Perception

Chapter 4: Sensation & Perception

1. Psychophysics

   • Threshold looking for Limits
   • Signal Detection Theory
     • -Signal detection theory proposes that the detection stimuli involves decision processes as well as sensory processes, which are both influenced by a variety of factors besides stimulus intensity -Hits (detecting signals when they are present) -Misses (failing to detect signals when they are present)
   • Perception without Awareness
     • -Subliminal perception-the registration of sensory input without conscious awareness -Subliminal perception has become tied up in highly charged controversies relating to money, sex, religion, and rock music. -Controversy began in 1957 when an executive named James Vicary placed hidden messages such as "eat popcorn" in a film showing at a theatre in New Jersey
   • Sensory Adaptation
     • -Sensory adaptation is a gradual decline in sensitivity due to prolonged stimulation -Sensory adaptation is a pervasive aspect of everyday life -Sensory adaptation is an automatic, built-in process that keeps people tuned in to the changes rather than the constants in their sensory input

2. Our Sense of Sight: The Visual System

   • The Stimulus Light
     • -Light is a form of electromagnetic radiation that travels as a wave, moving, naturally enough, at the speed of light -Amplitude (height) -Wavelength (the distance between peaks)
   • The Eye: A Living Optical Instrument
     • -The eyes serve two main purposes: They channel light to the neural tissue that receives it, called the retina and they house that tissue -Light enters the eye through a transparent window at the front, the cornea -The lens is the transparent eye structure that focuses the light rays falling on the retina
   • The Retina: The Brain's Envoy in the Eye
     • -The retina is the neural tissue lining the inside back surface of the eye; it absorbs light, processes images, and sends visual information to the brain -Cones are specialized visual receptors that play a key role in daylight vision and colour vision -The fovea is a tiny spot in the centre of the retina that contains only cones; visual acuity is greatest at this spot
   • Vision and the Brain
     • -Optic chiasm- the point at which the optic nerves from the inside half of each eye cross over and then project to the opposite half of the brain -feature detectors, neurons that respond selectively to very specific features of more complex stimuli -visual agnosia-an inability to recognize objects
   • Viewing the world in colour
     • -Subtractive colour mixing works by removing some wavelengths of light, leaving less light than was originally there -additive colour mixing works by superimposing lights, putting more light in the mixture than exists in any one light by itself -the trichromatic theory of colour vision holds that the human eye has three types of receptors with differing sensitivities to different light wavelengths

3. The Visual System: Perceptual Processes

   • Perceiving Forms, Patterns, & Objects
     • -Reversible figure, a drawing that is compatible with two interpretations that can shift back and forth -perceptual set-a readiness to perceive a stimulus in a particular way  -A perceptual set creates a certain slant in how someone interprets sensory input
   • Looking at the Whole Picture: Gestalt Principles
     • -The phi phenomenon is the illusion of movement created by presenting visual stimuli in rapid succession -Distal stimuli are stimuli that lie in the distance  -The proximal stimuli, the stimulus energies that impinge directly on sensory receptors
   • Perceiving Depth or Distance
     • -Depth perception involves interpretation of visual cues that  indicate how near or far away objects are -Binocular depth cues are clues about distance based on the differing views of the two eyes -Retinal disparity, which refers to the fact that objects project images to slightly different locations on the right and left retinas, so the right and lest eye see slightly different views of the object
   • Perceptual Constancies in Vision
     • -When a person approaches you from a distance, his or her image on your retinas gradually changes in size -a perceptual constancy is a tendency to experience a stable perception in the face of continually changing sensory input
   • The Power of Misleading Cues: Optical Illusions
     • -an optical illusion involves an apparently inexplicable discrepancy between the appearance of a visual stimulus and it's physical reality -one famous optical illusion is the Muller-Lyer illusion -People from a variety of non-western cultures are less susceptible to the Muller-Lyer illusion than Western samples

4. Our Sense of Hearing:The Auditory System

   • The Stimulus: Sound
     • -sound waves are vibrations of molecules, which means that they must travel through some physical medium such as air -they move at a fraction of the speed of light -like light waves sound waves are characterized by their amplitude, their wavelength, and their purity 
   • Human Hearing Capacities
     • -wavelengths of sound are described in terms of their frequency, which is measured in cycles per second, or hertz -Humans can hear sounds ranging from 20 Hz up to a high of about 20 000 Hz -The greater the amplitude of sound waves, the louder the sound perceived
   • Sensory Processing in the Ear
     • -Cochlea, a fluid filled coiled tunnel that contains the receptors for hearing -The basilar membrane, which runs the length of the spiralled cochlea, holds the auditory receptors -The auditory receptors are called hair cells because of the tiny bundles of hairs that protrude from them
   • Auditory Perception: Theories of Hearing
     • -Place theory, holds that perception of pitch corresponds to the vibration of different portions, or places, along the basilar membrane -Frequency theory holds that perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates -The current thinking is that pitch perception depends both on place and frequency coding of vibration along the basilar membrane
   • Music and It's Effects
     • -Music training can induce functional and morphological changes in the brain

5. Our Chemical Senses: Taste & Smell

   • Taste: The Gustatory System
     • -The gustatory receptors are clusters of taste cells found in the taste buds that line the trenches around tiny bumps on the tongue -There are four primary tastes: sweet, sour, bitter, and salty -Umami, Japanese word for savoury taste of glutamate found in foods like meats and cheeses
   • Smell: The Olfactory System
     • -The physical stimuli are chemical substances-volatile ones that can evaporate and be carried in the air -Pheromones are chemical messages, typically imperceptible, that can be sent by one organism and received by another member of the same species -The physical stimuli for touch are mechanical , thermal, and chemical energy that impinge on the skin
   • Feeling Pressure
     • -The sense of touch is set up to meet this need for tactile localization with admirable precision and efficiency -Skin patches, which vary considerably in size are the functional equivalents of receptive fields in vision -The nerve fibres that carry incoming information about tactile stimulation are routed through the spinal cord to the brainstem
   • Feeling Pain
     • -The perception of pain is crucial to survive -The receptors of the brain are mostly free nerve endings in the skin -Pain is not an automatic result of certain types of stimulation

6. Our Other Senses

   • The Kinesthetic System
     • -The kinaesthetic system monitors the positions of the various parts of the body -The kinesthetics system allows you to double-check these locations (limbs) -The receptors for kinaesthetic sense reside in joints, indicating how they are bending
   • The Vestibular System
     • -A vestibular system, which responds to gravity and keeps you informed of your body's location in space -It provides the sense of balance or equilibrium, compensating for changes in the body's position -Shares space in the inner ear with  the auditory system

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