Chapter 4: Sensation and Perception

Chapter 4: Sensation and Perception

1. 1) Psychophysics: Basic Concepts and Issues

   • 1. Thresholds: Looking for Limits
     • A threshold is a dividing point between energy levels that do and do not have detectable effect.
     • An absolute threshold for a specific type of sensory input is the minimum amount of stimulation that an organism can detect.
     • A just noticeable difference is the smallest difference in the amount of stimulation that a specific sense can defect.
     • Weber's law states that the size od a just noticeable difference is a constant proportion of the size of the initial stimulus.
   • 2. Signal-Detection Theory
     • A signal detection theory proposes that the detection of stimuli involves decision processes as well as sensory processes, which are both influenced by a variety of factors besides stimulus intensity.
     • Detectability is measured in terms od probability and depends on decision making processes as well as sensory processes.
   • 3. Perception without Awareness
     • Subliminal perception is the registration od sensory input without conscious awareness
       • Subliminal perception has become tied up in highly charged controversies relating to money, sex religion, and rock music.
   • 4. Sensory Adaption
     • Sensory Adaptation is a gradual decline in sensitivity due to prolonged stimulation
       • -Automatic.
       • -Allows people to ignore the obvious and focus on the changes in their environment that may stimulate threats to safety

2. 2) Our Sense of Sight: The Visual System

   • 1. The Stimulus: Light
     • Light is a form of electromagnetic radiation that travels as a wave, moving, naturally enough, at the speed of light.
       • Light waves very in amplitude (height) and wavelength (the distance between peaks)
   • 2. The Eye: A Living Optical Instrument
     • The eyes have two main purposes: they channel light to neutral tissue that receives it, called the retina and they house that tissue.
     • Light enters at the cornea.
     • The Lens is the transparent eye structure that focuses on the light rays falling in the retina
     • The pupil is the opening in the centre of the iris that helps regulate the amount of light passing into the rear chamber of the eye.
   • 3. The Retina: The Brains Envoy in the Eye
     • The retinal is the neural tissue lining the inside back surface of the eye. It absorbs light, processes images, and send visual information to the brain.
     • Optic disk is a hole in the retina where the optic nerve fibres exit the eye.
     • Cones are specialized visual receptors that play a key role in daylight vision and colour vision.
     • Rods are specialized visual receptors that play a key role in night vision and peripheral vision.
   • 4. Vision and the Brain
     • Optic Chiasm is the point at which the optic nerves from the inside half of each eye cross over then project to the opposite half to the brain
       • Prosopagnosia is an inability to recognize familiar faces
     • Visual Agnosia is an inability to recognize objects
   • 5. Vision for Perception and Vision for Action
     • Goodall and Humphrey distinguish two functions that vision serves.
       • First: create and internal representation or model of external world.
         • Second: process of controlling ones actions that are directed at those objects.
   • 6. Viewing the World in Colour
     • Subtractive colour mixing works by removing some wavelengths of light.
     • Additive color mixing works by superimposing lights, putting more light in the mixture than exists in any one light by itself
     • Trichromatic theory of colour vision holds that the human eye had three types of receptiors with differiing sensitives to different light wavelengths

3. 3) The Visual System: Perceptual Process

   • 1. Perceiving Forms, Patterns, and Objects
     • Reversible figure, a drawing that is compatible with two interpretations that can shift back and fourth
     • Perceptual set is a readiness to perceive a stimulus in a particular way.
     • Feature analysis is a process that detects specific elements in visual input and assembling them into a more complex form.
   • 2. 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.
     • Perceptual hypothesis is an inference about which distal stimuli could be responsible for the proximal stimuli sensed.
   • 3. Perceiving Depth or Distance
     • Depth perception involves interpretation of visual cues that indicate how near or far away objects are.
       • Binocular depth is cues about distance based on the differing views of the two eyes.
     • Pictorial depth cues are about distance that can be given in a flat picture.
   • 4. Perceptual Constancies in Vision
     • A perceptual constancy is a tendency to experience a stable perception in the face of continually changing sensory input.
   • 5. The Power of Misleading Cues: Optical Illusions
     • An optical illusion involves an apparently inexplicable discrepancy between the appearance of a visual stimulus and its physical reality.

4. 4) Our Sense of Hearing: The Auditory System

   • 1. The Stimulus: Sound
     • Sound waves are vibrations of molecules which means they must travel through some physical medium, such as air.
     • Characterized by: amplitude, and purity.
   • 2. Human Hearing Capacities
     • Wavelengths are described in their terms of frequency.
       • Measured in cycles per second.
         • Amplitudes also depends on frequency.
   • 3. Sensory Processing in the Ear
     • Like your eyes, your ears channel energy tp the tissue that receives it.
     • External ear consists of the pinna, a sound collecting cone.
     • Cochlea is a fluid filled coiled tunnel that contains the receptors for hearing.
   • 4. Auditory Perception: Theories of Hearing
     • Frequency theory holds that perception pf pitch corresponds to the rate, or frequency at which the entire basilar membrane vibrates.
       • Place theory holds that perception pf pitch corresponds to the vibration of different portions, or places, along the basilar membrane.
   • 5. Music and Its Effects
     • Our auditory system provides us with one way to experience and relate to the world.
     • Music is something that most of us enjoy
       • Music is apart of our culture and each seems to shape the other.

5. 5) Our Chemical Senses: Taste and Smell

   • 1. Taste: The Gustatory System
     • The physical stimuli for the sense of taste are chemical substances that are soluble. (dissolve in water).
       • 4 primary tastes: sweet, salty, bitter, and sweet.
         • Women are more likely to be super tasters than men.
           • Gender gap in this trait may have been evolutionary
   • 2. Smell: The Olfactory System
     • Humans are usually characterize as being relatively insensitive to smell; often the only thing we can say about an odour is whether it ispleasent or not.
       • In many ways, the sense of smell is much like the sense of taste.
         • Pheromones are chemical messages, typically imperceptible that can be sent by one organism and received by another member of the same species.

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

   • 1. Feeling Pressure
     • If you get bite by a mosquito, you will panic and appreciate the need to quickly know where tactile stimulation is coming from.
       • The sense of touch is set up to meet this need for tactile localization with admirable precision and efficiency.
   • 2. Feeling Pain
     • An unpleasant pain is the sensation of rain is crustal to survival.
       • Pain is a warning system that tells people when something is wrong, and could harm the individual.
         • Receptors for coin are mostly free nerve endings in the skin.
           • Pain messages are sent to the brain through fast, or slow pathways.

7. 7) Our Other Senses

   • 1. The Kinaesthetic System
     • Monitors the positions of the various parts of the body.
   • 2. The Vestibular System
     • Responds to gravity and keeps you informed about your bodies location in space.