Sensation & Perception

Sensation & Perception

  • Sensation: process by which stimulated receptors make a pattern of neural messages (brain stimuli) and makes our experience of the stimulus
    • Bottom up processing (sensation): analysis of the stimulus begins with sense receptors → brain
  • Perception: a mental process that gives meaning to incoming sensory patterns
    • Muller-lyer illusion
    • Top down processing (perception): we use our experiences to construct perceptions
    • Perceptual set: mental predisposition to see one thing, not another, due to top down processing
    • Cocktail party effect: shows selective attention
    • Inattentional blindness
    • Change blindness
  • Absolute threshold
  • Subliminal threshold: you would identify it being there <50% of time
  • Difference threshold: smallest amount which a stimulus can change and the difference is detected.
    • AKA Just noticeable difference: minimal amount of change in the signal that is recognizable.
  • Weber's law: to perceive as different 2 stimuli must differ by a constant minimum percentage
    • Light intensity- 8%
    • Weight- 2%
    • Tone frequency- 0.3%
  • Signal Detection Theory (SDT): predicts how and when we detect a faint stimuli in a background of noise
    • Assumes there is no absolute threshold
    • Detection depends on:
    • Experience
    • Expectations
    • Motivation
    • Fatigue
  • SDT matrix: observed decides whether to heat or not, based on signal being present or not
  • Subliminal messaging:
    • Works by priming
    • Unconsciously activating associations
  • Sensory adaptation: diminished physical sensitivity as a result of constant stimulation
    • We no longer receive stimuli
  • Habituation: when one no longer attends to something after a long period of time
  • Transduction: conversion of stimulation into a neural message
    • Brain does not interact w/ world directly, sense organs do
  • All senses tap into a diff form of stimulus
    • All processed in own brain region
  • Vision:
    • Most complex
  • How eye works:
    • Retina takes light and makes it a neural signal
  • Color:
    • Hue: dimension of color determined by wavelength of light
    • Wavelength: distance between peak of one wavelength to next
    • Intensity: brightness
  • The eye:
    • Cornea: outer covering of eye
    • Pupil: adjustable opening in center of eye, where light enters
    • Iris: ring of muscle tissue that forms colored portion of eye
    • Dilates & constricts in response to changing light intensity
    • Lens: behind cornea, changes shape to help focus image
    • People w/ glasses: faulty lens
      • Accommodation: eyes lens changes shape to focus image
      • Nearsighted: nearby objects are more clear
      • Farsight: far objects are more clear
      • Acuity: sharpness of vision
    • Retina: light sensitive inner surface, has rods & cones, layer of cells, where transduction takes place
    • Blind spot: where optic nerve leaves eye, can’t see here
    • Fovea: best part of vision, cones clustered
    • Optic nerve: carries nerve impulses from eye to brain
  • Processing visual info
  • LGN: in thalamus
  • Feature detector cells: respond to specific features
  • Parallel processing: all done at the same time
  • Scene → parallel processing: bottom up processing
  • Recognition: top down processing
  • Theory of color vision:
    • Trichromatic theory: retina has 3 receptors sensitive to red, blue, green
    • Color blindness: ishihara test, people are blind to green & red colors
    • Opponent processing: some aspects of color perception are hard to explain by trichromatic theory
    • We have 4 primary colors combined in pairs
      • Red-green
      • Blue-yellow
      • Black-white
      • Green → red
      • Black → white
      • Yellow → blue
  • Visual organization
    • Gestalt (form or whole)
    • Whole is more than sum of its parts
    • Figure ground
    • Grouping
    • Group by proximity
    • By continuity
    • Closure
    • Law of pragnanz: whatever is easiest to see us what we will see
    • Depth perception
    • Visual cliff
    • Binocular depth cues
      • Retinal disparity: 2 diff images in each eye
      • Convergence: when eyes move inward, this gives depth cues that something is coming at you
      • Monocular depth cues:
      • Relative size: closer objects are larger
      • Interposition: somethings closer
      • Linear perspective: lines converge in distance
      • Relative motion: objects near you seem to move quicker than far away objects
      • Texture gradient: more texture when closer
    • autokinetic effect - stationary beam of light is projected on a wall in an otherwise completely dark room If you stare at the dark light long enough the light appears to move
    • Stroboscopic movement = flip book
  • Color constancy: colors are the same, even though they look diff in diff lighting
  • Brightness constancy
  • Shape constancy:
  • Size constancy: when something goes far from us it gets smaller
    • Moon illusion: moon appears bigger when it's just above the horizon.
  • Visual interpretation:
    • Restored vision
    • Critical period
    • Perceptual adaptation: we change something about our visual system, we can adapt

Hearing:

  • Energy of vibrational objects, transferring the surrounding air as vibrating objects
    • Frequency: number of cycles completed by a wave in a given amount of time
    • Determines pitch
    • Amplitude: how loud it is, strength of wave
  • Outer part of ear- pinna
  • Cochlea is where transduction occurs
    • Wave → neural signal
  • Ear:
    • Middle ear: transmits drum vibrations
  • Audition (hearing)
    • Place theory: links the pitch we hear to where the cochlea’s membrane is stimulated
    • Works good w/ high pitch sounds
    • Frequency theory: brain identifies pitch of sounds according to how rapid neural impulses fire
    • Hair cells will volley (fire alternately)
  • Deafness
    • Conduction: not able to hear bc of damage to structures of middle ear, or a blockage (wax)
    • Nerve: inability to transmit impulses from cochlea to brain, transduction is impaired
    • Can get cochlear implant

Position & movement:

  • Vestibular sense: body orientation & balance.
  • Kinesthetic sense: ability to track your own body movements/parts

Smell

  • Olfaction
  • Odors interact w/ receptor proteins associated w/ hairs in the nose- olfactory cells (in temporal lobe)
  • Hairs convey info to olfactory bulbs
  • Anosmia- loss of smell
  • Pheromones: chemically produced odors that send messages
  • *does not go to thalamus

Taste

  • Gustation
  • main qualities
    • Sweet
    • Savory
    • Sour
    • Bitter
    • Salty
  • Chemical sense
  • Nerves carry taste messages to brain in frontal lobe
  • Frequently replaced
  • Can be damaged (smoke, alc, hot foods)

Touch

  • Somatosensory cortex
  • Skin is sensitive to:
    • Pressure
    • Pain
    • Gate control theory
      • Gate that can block/allow pain signals
    • Temp (warm/cold)
  • Synesthesia: combo of senses