Sensory Processes

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  • Sensory Processes
    • Visual Processes
      • Photoreceptors
        • The photoreceptors in the retina are the start of real visual processing
        • They are 2 kinds: rods & cones
          • Cones come in 3 kinds (red, green, blue) to detect different wavelengths of light
            • Deuteranopia: problem with green cones, causing green to appear grey
            • Protanopia: a problem with blue cones, causing blue to become grey
        • The forvea (yellow spot) has only cones
        • The blind spot has no rods or cones
        • Rods can work well in low light, but cones need a lot of light to be stimulated
      • Can be physiological (adaptation) or psychological (perception)
      • Emmetropic
        • When the power of the lens system is appropriate for size of eye
        • The ciliary muscles contract or relax, altering lens shape to focus light beams on the retina
        • Optical Defects
          • Myopia
            • When the lens is too strong for your eye and light beams cross one another before reaching retina
            • Short sightedness
          • Hypermetropia
            • Opposite of myopia, Longsightedness
            • When the lens is too weak and light beams do not have a chance to meet
      • Visual Acuity
        • The ability of eyes to differentiate between the detailed features of what we see
        • Refraction occurs at cornea & lens
        • The focusing of eyes
      • Convergence
        • The movement of eyes to ensure that the image on each retina is in corresponding locations
        • An imbalance causes double vision or discomfort
      • How it works
        • Receptor cells > Bipolar cells > Ganglion Cells > Optic nerve > LGN ( P cells to one bit, M cells to another)
        • After the info reaches the retinotopic LGN, it carries on the the visual cortex
    • Auditory Processes
      • Alarm Design
        • A lot of factors need to be taken into account
          • eg. Damage level
          • Average hearing ability
          • Length of sound
          • Pitch
        • If the noise is too loud:
          • People get stressed
          • Communication is hindered
          • Work efficiency is reduced
      • Auditory Attention
        • The selection or rejection of a noise is based on:
          • Location
          • Pitch
          • Rhythm
          • Location of the sound in relation to person
          • Intensity
        • Cocktail party effect
          • Cherry (1953)
          • Attention is automatically shifted if you hear your name
      • How does it work?
        • Sound waves enter the ear canal, causing the eardrum to vibrate
        • The vibrations pass through 3 connected bones in the middle ear region
        • This sets fluid in the inner ear working
        • These fluid vibrations are converted to electrical impulses which are carried to the brain via the auditory nerve
    • Tactile Processes
      • Sensitive in a different way
      • Tactile processes need more not less info
      • e.g. car stereos are easier to use if they are buttons and not touch
    • Information Processing
      • Signal Detection Theory
        • How we make decisions under conditions of uncertainty
        • Origins in Sonar
        • What level does it take for a signal to become a signal
        • Green & Swets (1954)
        • The object of a signal is to create more hits than ,misses
        • Factors involved: Strategy/ Strength
          • You could have conservative or liberal strategies
        • If difference between signal and noise is large, its an easy task
    • Controlled vs Automatic Processes
      • Schneider & Shiffrin (1977)
      • Controlled processes have a limited capacity + require attention
      • Automatic processes are not capacity limited
      • APs are very difficult to alter once learnt
      • Strope Test
        • Kahneman & Colquhoun (1975)
        • Colours were written in different inks, ppts were asked to state the colour of the ink

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