Psychophysics

Psychophysics

Sensation
1. Detection of physical energy emitted or reflected by physical objects
2. Occurs when energy in the external environment or the body stimulates receptors that receive, translate raw sensory information from the external, and transmit it to different parts of the brain
3. "Raw" material for perception
4. "Entry Level"
  1. Data Driven
5. Bottom-up processing
6. Three key concepts
  1. Transduction
    1. Converts physical stimuli into neural impulses
      1. aka sensory stimuli
  2. Coding
    1. Converts particular sensory stimuli into specific sensations
  3. Sensory Reduction
    1. Filters and analyzes incoming sensations before sending a neural impulse to the brain
7. Neural impulses gained through the senses are sent to various parts of the brain
  1. Doctrine of specific nerve energies
8. Synesthesia
  1. Mixing of the senses
    1. e.g. Coloured letters
Perception
1. Process by which the brain selects, organizes and interprets sensory data
2. Top-down processing
Study of how physical stimuli are translated into physiological experience (Fechner, 1860)
Absolute Threshold
1. The smallest quality of physical energy that can be reliably detected by an observer
  1. Vision
    1. A single candle flame from 30 miles on a dark, clear night
  2. Hearing
    1. The tick of a watch from 20 feet in total quiet
  3. Smell
    1. 1 drop of perfume in a 6-room apartment
  4. Touch
    1. The wing of a bee on your cheek, dropped from 1 cm
  5. Taste
    1. 1 tsp. Sugar in 2 gal. water
Difference Threshold
1. Smallest difference in stimulation that can be reliably detected by an observer
2. Just Noticeable Difference (JND)
3. Weber's Law
  1. JND is a constant proportion of the size of the initial stimulus
4. Fechner's Law
  1. Psychophysical Scaling
    1. Using these scales to measure stimulus and make conclusions on our experiences
5. Signal-Detection Theory
  1. A theory that divides the detection of a sensory signal into a sensory (stimulus) and decision (decision made) process
6. Subliminal Perception
  1. "-liminal"
    1. Threshold
  2. "Sub"
    1. Below
Sensory Adaptation and Deprivation
1. Adaptation
  1. The reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitious
  2. Prevents us from having to continuously respond to unimportant information
2. Vision
  1. Stimulus
    1. Light
      1. Electromagnetic Radiation
        Amplitude
        Perception of brightness/intensity
        Wavelength
        Perception of colour/hue
        Purity/Range
        Mix of wavelengths
        Perception of saturation/richness of colours
  2. The Eye
    1. Converting light into neural impulses
    2. Components
      1. Cornea
        Where light enters the eye
      2. Lens
        Focuses the light rays on the retina
      3. Iris
        Coloured ring of muscle, constricts or dilates via amount of light
      4. Pupil
        Regulates the amount of light
    3. Saccades
      1. The eye msucles making a rapid step-like rotation
      2. Brief fixations at various parts of the stimuli
    4. Retina
      1. Receptors for vision are located in the retina
        Rods
        Light receptors
        Peripheral
        Cones
        Colour receptors
      2. Fovea
        A pit full of cones
        Responsible for our sharpest vision
      3. Blind Spot (Optic Disk)
        Near the fovea
        No visual light receptors
      4. Lateral Antagonism
        Occurs when neural activity in a cell opposes actively in surrounding cells
        Allows the retina to compare the light falling in a specific area against general lighting
Hubel and Wiesel
1. Early 1960s
  1. Microelectrode recording of axons in primary vision cortex of animals
  2. Discovered feature detectors
    1. Neurons that respond selectively to lines, edges, etc.
2. Later research
  1. Cells specific to faces in the temporal lobes of monkeys and humans
Basics of Colour Vision
1. Refer to "Sensory of Adaptation and Deprivation" for information on light waves
2. Trichromatic Theory
  1. Our vision is based on three colours that combine to create other colours
  2. Simple Visual Cells
3. Opponent Process Theory
  1. Three pairs of colours
    1. Green/Red, Blue/Yellow, Black/White
    2. After Images
    3. Complex Visual Cells
Perceiving Forms, Patterns, and Objects
1. Reversible figures
2. Brain needs context
3. Perceptual Sets
4. Opposite views of sensation-perception process
  1. Feature Detection Theory
    1. Bottom-Up Processing
  2. Form Perception
    1. Top-Down Processing
  3. Subjective Contours
5. Principals of perception
  1. Gestalt Psychology
    1. Two Guiding Principles
      1. Large picture perceived before component parts
      2. Nervous system automatically selects simplest interpretations
    2. Phi Phenomenon
      1. Critical flicker fusion
        Movie Frames
    3. Principles of form perceptions
      1. Figure-Ground
      2. Proximity
      3. Similarity
      4. Simplicity
      5. Continuity
      6. Closure
6. Distal vs. Proximal Stimuli
7. Depth and distance perception
  1. Binocular Cues
    1. Clues from both eyes together
      1. Retinal Disparity
      2. Convergence
  2. Monocular Cues
    1. Clues from a single eye
      1. Motion Parllax
      2. Accomodation
      3. Pictorial Depth Cues
8. Perceptual Constancies
  1. stable perceptions amid changing stimuli
    1. Size
    2. Shape
    3. Brightness
    4. Hue
    5. Location in space
9. Optical Illusions
  1. Discrepancy between visual appearance and physical reality
10. Cultural differences
  1. Perceptual hypotheses at work in the Mueller-Lyer Illusion
11. Hearing: The Auditory System
  1. Stimulus
    1. Sound Waves
      1. Amplitude
        Loudness
        Sound Pressure
        Decibels (db)
        Perceived loudness increases as decibels increase
    2. Wavelength
      1. Pitch
      2. Frequency
        Increase in frequency means that there's an increase in pitch
    3. Purity/Complexity
      1. Timbre
12. The Ear
  1. External Ear (Pinna)
    1. Collect Sound
  2. Middle Ear
    1. The Ossicles
      1. Hammer
      2. Anvil
      3. Stirrup
  3. Inner Ear
    1. Cochlea
      1. A fluid-filled, coiled tunnel
      2. Contains the hair cells, the auditory receptors
      3. Lined up on the basilar membrane
13. Theories of Hearing
  1. Hermann von Helmholtz (1863)
    1. Place Theory
  2. Other researchers (Rutherford, 1886)
    1. Frequency Theory
  3. Georg von Bekesy (1947)
    1. Travelling Wave Theory
14. Taste (Gustation)
  1. Physical Stimulus
    1. Soluble chemical substances
15. Smell (Olfaction)
  1. Physical Stimulus
    1. Substances carried in the air
  2. Only sense that does not go through the thalamus
16. Touch
  1. Physical Stimulus
    1. Mechanical (touch), thermal (temperature), chemical (pain)
17. Kinesthetic and Vestibular System
  1. Kinethesis
    1. Knowing the positions of the parts of your body
      1. Receptors in joints/muscles
  2. Vestibular
    1. Equilibrium/Balance
      1. Semicircular Canals

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