Sensation & Perception

Sensation & Perception

1. Psychophysics: Basic Concepts and Issues

   • Thresholds: Looking for Limits
     • Absolute thresholds are minimum detectable stimulus for specific types of sensory input Weber's law states that the size of a just noticeable difference (JND) is a constant proportion of the size of the initial stimulus.
   • Signal Detection Theory
     • Signal Detection Theory proposes that the detection of the stimuli involves decision processes as well as sensory processes
   • Perception without Awareness
     • Subliminal Perception is the registration of sensory input without conscious awareness; it is a genuine phenomenon, but the effects tend to be very weak
   • Sensory Adaptations
     • Sensory Adaptation is the gradual decline in sensitivity to a stimulus with prolonged stimulation

2. Our Sense of Sight: The Visual System

   • 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    
   • 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)    
   • 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

   • Percieveing 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     
   • 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    
   • Percieving Forms, Patterns and 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     

4. Our Sense of Hearing: The Auditory System

   • 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    
   • 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     
   • Music and its Effects
     •           Music training can induce functional and morphological changes in the brain    
   • 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    

5. Our Chemical Senses: Taste and Smell

   • 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    
   • 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    

6. Our Sense of Touch: Sensory Systems in the Skin

   • 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    
   • Feeling Pressure
     • The nerve fibres that carry incoming information about tactile stimulation are routed through the spinal cord to the brainstem    

7. Our Other Senses

   • 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    
   • 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    

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