Sensation & Perception

Psychophysics: Basic Concepts and Issues
1. Psychophysics: The study of how physical stimuli are translated into psychological experience
2. Thresholds: A dividing point between energy levels that do and do not have a detectable effect
  1. Absolute Threshold: For a specific type of sensory input is the minimum amount of stimulation that an organism can detect
  2. JND: The smallest difference in the amount of stimulation that a specific sense can detect
    1. Weber's Law: States that the size of a just noticeable difference is a constant proportion of the size of the initial stimulus
3. 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.
  1. Hits: Detecting signals when they are present
  2. Misses: Failing to detect signals when they are present
  3. False Alarms: Detecting signals when they are not present
  4. Correct Rejections: Not detecting signals when they are absent
  5. Detectability: Measured in terms of probability and depends on decision-making processes as well as sensory processes
4. Subliminal Perception: The registration of sensory input without conscious awareness
5. Sensory Adaption: A gradual decline in sensitivity due to prolonged stimulation
Our Sense of Sight: The Visual System
1. The Stimulus: Light
  1. We need light to see
  2. Light waves vary in amplitude (height) and wavelength (distance between peaks)
  3. Measured in Purity: How varied the mix is
  4. Ultraviolet = shorter wavelengths
  5. Infrared = longer wavelengths
2. The Eye: A living Optical Instrument
  1. Two main purposes
    1. 1. Channel light to the neural tissue that receives it (retina)
    2. 2. Houses the Retina
  2. Lens: Transparent eye structure that focuses the light rays falling on the retina
    1. Accommodation: When the curvature of the lens adjusts to alter visual focus. Closer = Fatter (rounder) and Distant = flatter
  3. Nearsightedness: Close objects are seen clearly but close distant objects appear blurry
  4. Farsightedness: Distant objects are seen clearly but close objects appear blurry
  5. Pupil: The opening in the centre of the iris that helps regulate the amount of light passing into the rear chamber of the eye
  6. Our eyes are in constant motion called Saccades and are important so we don't experience sensory adaption and lose sight of things around us
3. The Retina: The Brain's Envoy in the Eye
  1. The neural tissue lining the inside back surface of the eye; it absorbs light, processes images, and sends visual information to the brain
  2. Processes images
  3. Optic Disk: a hole in the retina where the optic nerve fibres exit the eye
  4. Two kinds of visual receptors located in the innermost layer of the retina
    1. Cones: Specialized visual receptors that play a key role in daylight vision and colour vision
      1. Visual Acuity: Sharpness and precise detail
      2. Fovea: A tiny spot in the centre of the retina that contains only cones; visual acuity is greatest at this spot
    2. Rods: Specialized visual receptors that play a key role in night vision and peripheral vision
  5. Dark Adaption: The process in which the eyes become more sensitive to light in low illumination
  6. Light Adaption: The process whereby the eyes become less sensitive to light in high illumination
  7. Optic Nerve: A collections of axons that connect the eye with the brain
  8. The Receptive Field: The Retinal area that when stimulated affects the firing of that cell
4. Visual Pathways to the Brain
  1. Optic Chiasm: The point at which the optic nerves from the inside half of each eye cross over and then project to the opposite hald of the brain
  2. LGN: Lateral Geniculate Nucleus where 90 percent of the axons from the retinas synapses are located and visual signals are processed.
5. Viewing the World in Colour
  1. Subtractive Colour Mixing: Works by removing some wavelengths of light, leaving less light than was originally there
  2. Additive Colour Mixing: Works by superimposing lights, putting more light in the mixture than exists in any one light by itself
  3. Trichromatic Theory: Colour vision holds that the human eye has three types of receptors with differing sensitivities to different light wavelengths
  4. Colour-blindness: Encompasses a variety of deficiencies in the ability to distinguish among colours
  5. Complementary Colours: Pairs of colours that produce grey tones when mixed together
  6. Afterimage: A visual image that persists after a stimulus is removed
  7. Opponent Process Theory: Holds that colour perception depends on receptors that make antagonistic responses to three pairs of colours
6. Vison and the Brain
  1. Feature detectors: Neurons that respond selectively to very specific features of more complex stimuli
  2. visual agnosia: An inability to reorganize objects
  3. Prosopagnosia: An inability to recognize familiar faces
Our Sense of Hearing: The Auditory System
1. Cochlea: Fluid-filled, coiled tunnel that contains the receptors for hearing
2. Basilar Membrane: Runs the length of the spiralled cochlea, holds the auditory receptors
3. Theories of Hearing
  1. Place Theory: Holds that perception of pitch corresponds to the vibration of different portions, or places, along the basilar membrane
  2. Frequency Theory: Holds that perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates

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Sensation & Perception

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	Created by Darby Milman about 8 years ago