Lecture #4 Sensation and Perception

    Cards (44)

    • Sensation
      Nervous system detects or encodes information from the environment
    • Perception
      How we interpret nerve sensations or give meaning to them
    • We do not perceive everything in the physical world
    • We miss events that happen around us, and even in front of us
    • We perceive things that aren't there
    • Perceptions are not true representations of the physical world
    • Three themes of perception
      • Perception depends on context
      • Perception is about objects
      • Perception is multimodal
    • Visible Light
      • Electromagnetic waves with wavelengths between 400 and 700 nanometers
      • Can be a wave, and also consists of particles known as photons
    • Light reflection
      Light bounces off of objects
    • Light refraction
      Light passes through objects and bends
    • Lens
      Bends (refracts) light so that it focuses on retina
    • Ciliary muscle

      Changes shape of the lens
    • Corrective measures for vision
      • Nearsightedness (myopia): objects focus in front of retina, fixed by concave lens
      • Farsightedness (hyperopia): objects focus behind retina, fixed by convex lens
    • Macula
      Center of retina
    • Rods
      Detect dark vs light and motion, located in visual periphery
    • Cones
      Detect colour and detail, three kinds, located in visual center
    • Trichromatic theory of colour vision
      Colour vision is influenced by the output of all 3 cone types, not a single cone type
    • Colour Contrast
      Colours are more vivid when they contrast with their background (context!)
    • Colour Constancy
      Objects appear the same colour despite changes in the lighting conditions
    • The lens of the eye focuses light waves on the retina; ciliary muscles control accommodation
    • Rods and cones of the retina transduce light energy into neural signals
    • The trichromatic theory states that colour vision is influenced by the output of all 3 cone types
    • Perception of colour depends on context
    • Gestalt Laws of Organization
      • Proximity: Perceive objects near each other as grouped together
      • Similarity: Perceive similar objects in groups
      • Continuity: Perceive parts as single, uninterrupted objects
      • Closure: Perceive stimuli as a whole entity, including illusory contours and negative space
    • Linear perspective
      Parallel lines converge in the distance, diverge closer to us
    • Monocular depth cues
      • Relative size: nearby objects appear larger than objects at greater distances
      • Relative height: faraway objects are higher in our view than closer objects
      • Familiar size: prior knowledge about the size of the object and how it should appear relative to other objects
      • Aerial perspective: distant objects appear more hazy because light is scattered by atmosphere
      • Motion parallax: distance estimated when viewing objects from two lines of sight
    • Stereopsis
      We see depth because of binocular disparity, or the differences in images between left and right eyes
    • Gestalt Laws of Organization let us group and combine visual features into coherent objects based on objects and past experiences
    • Linear perspective, relative height and size, familiar size, aerial perspective, and motion parallax are monocular cues that let us see depth with one eye
    • Binocular disparities, or the differences in images between left and right eyes, let us experience stereopsis, or using two eyes to see in 3 dimensions
    • Perception is multimodal
      We perceive objects through more than one "mode" or sense
    • Sound
      Mechanical vibrations we detect with our ears
    • Sound amplitude

      Related to loudness
    • Sound frequency
      Cycles per second, related to pitch
    • Decibels (dB)
      • Ratio scales, can be used to describe any ratio of any value
      • dB sound pressure level (SPL): ratio of measured sound pressure amplitude to weakest sound pressure humans can hear at 1000 Hz
      • dB SPL (physical energy) is not the same thing as loudness (mental experience)
    • Frequencies and sound levels we can hear
      • Frequency: 20 to 20,000 Hz
      • Level: -10 to ~140 dB SPL
    • Cochlea
      Separates high and low pitches
    • Sound transduction
      • Basilar membrane motion
      • Hair cells
    • Speech perception is multimodal: hearing and vision combine
    • Visual speech constrains the possible options for words that we hear
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