Sensation & Perception

Sensation - our sensory receptors receive info from stimuli in the environment

Perception - our brains organizing and interpreting sensory info, gives us our ability to recognize, categorize, and understand

• Bottom-up processing - makes sense of the information (new experiences)
  • sensory receptors → brain (younger in life)
• Top-down processing - our brains construct perceptions based on our previous experiences and expectations (known experiences)
  • brain → sensory receptors (older in life)

Selective Inattention:

• Change blindness - failure to notice changes in the environment
• Inattentional blindness - we fail to see easily visible objects when our attention is directed to something else

Perceptual Set - pre-conceived way of interpreting a stimulus that is usually culturally or socially reinforced

• eg. sensor bleeps

Structure and Functions of the Eye

Properties of Light:

• Wavelength - determines the color/hue we see (distance between light wave peaks)
  • short = more blue-ish colors; long = more red-ish colors
• Intensity of light waves (aka amplitude) determines the brightness of the colors we see
  • low intensity = dull colors; high intensity = bright colors

The Eye:

• Cornea - the outer layer that protects the eye, also bends light waves in order to start focusing them

• Pupil - the center of the eye-opening, it expands and contracts due to the action of the iris (colored muscle around the pupil)

• Lens - lies behind the pupil, focuses the incoming light rays onto the retina through accommodation (changing shape in order to focus the object clearly)

• Retina - the inner surface of the eye, highly sensitive to light; contains rods, cones, and neurons; the images focus on it are upside down

  • Rods - receptor cells that detect white, black, and grey
  • great at seeing in low light; poor at seeing color and detail
  • Cones - receptor cells that detect color
  • poor at seeing in. low light; great at seeing color and detail
  • Bipolar cells - activate in response to the rods and cones being stimulated
  • Ganglion cells - neurons that converge to form the optic nerve, which leaves the back of the eye and goes to the brain

• Fovea - the point on the retina where images are focused; the cones cluster around it; the most sensitive area

• Blind spot - no rods or cones where the optic nerve leaves the eye causing a blind spot in our vision

  

Visual Organization and Interpretation

Visual Organization:

• Gestalt - an organized whole; gestalt psychologists emphasize our tendency to integrate pieces of info into meaningful wholes
• Figure-ground - the organization of the visual field into objects that stand out from their surroundings
• Grouping - the perceptual tendency to organize stimuli into coherent groups
• Depth perception - the ability to see objects in 3D although the images that strike the images are 2D
• Visual Cliff - a laboratory device for testing depth perception in infants and young animals
• Binocular Cues - depth cues, such as retinal disparity
  • depend on the use of both eyes
• Retinal Disparity - a binocular cue for perceiving depth
• Monocular Cues - depth cues, such as interposition and linear perspective
  • available to either eye alone
• Phi phenomenon - an illusion of movement created when 2 or more adjacent lights blink on and off in quick succession
• Perceptual constancy - perceiving objects as unchanging even as illumination and retinal images change
• Color constancy - perceiving familiar objects as having consistent color even if changing illumination alters the wavelength reflected by the object

Visual Interpretation:

• Perceptual adaptation - in vision, the ability to adjust to an artificially displaced or even inverted visual field

The Other Senses

Touch

• 4 basic skin sensations: pressure, warmth, cold, and pain
• Pain is dependent on genes, physiology, experience, attention, surrounding culture, and sex
  • Nociceptors - sensory receptors that detect hurtful temperatures, pressures, and chemicals
  • Gate-control theory - that the spinal cord contains a neurological gate that blocks pain signals or allows them to passion onto the brain
  • Phantom limb sensation - when it misinterprets the spontaneous central nervous system activity that occurs in absence of normal sensory input

Taste

• 4 basic tastes: sweet (energy), salty (sodium), sour (toxic?), bitter (poison?), and umami (proteins)

Smell

• we can recognize long-forgotten odors and their associated memory

Body Position & Movement

• kinesthesia - your sense of the position and movement of your body parts
• vestibular sense - the sense of body movement and position including the sense of balance

Sensory Interaction - the principle that one sense may influence another

• eg. physical warmth → social warmth
• embodied cognition - the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments

Hearing

Sound Waves: (sound is measured in decibels)

• Audition - the sense or act of hearing
• Amplitude - determines the loudness
• Frequency - determines pitch; the number of complete wavelengths that pass a point in a given time
• Pitch - a tone’s experienced highness or lowness

The Ear

• Middle ear - the chamber between the eardrum and cochlea containing three bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window

• Cochlea - a coiled, bony fluid-filled tube in the inner ear; sound waves travel through here triggering nerve impulses

• Inner ear - the innermost part of the ear; contains the cochlea, semicircular canals, and vestibular sacs

• Hearing loss:

  • Sensorineural hearing loss - caused by damage to the mechanical system that conducts sound waves to the cochlea
  • Conduction hearing loss - caused by damage to the mechanical system that conducts sound waves to the cochlea

• Cochlear implant - a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded in the cochlea

• Place theory - the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated

• Frequency theory - the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of the tone

• Absolute threshold - how much of a stimulus do we need to detect it 50% of the time

  • eg. concert 110 dB, talking 50 dB, >100 dB is likely to cause hearing damage

• Outer ear - channels sound waves to the eardrum

• Basilar membrane - moves caused by cochlea vibrations; covered with hair cells

• Auditory (cochlear) nerve - axons in the inner ear send auditory signals to the temporal lobe

Perception of loudness:

• louder sounds activate more hair cells
• people with hearing loss often lose their sensitivity to soft sounds but will respond to loud sounds
• instead of making everything louder, hearing aids compress sound (bring soft sounds up to the level of louder sounds and smooths out the changes in loudness)

Visual Processing

Feature detection

• feature detectors - specialized neurons in the visual cortex, recognize/respond to specific features of a stimulus (lines, angles, edges, etc)
  • pass info to other brain areas that recognize/process the more complex features
  • our brains have a visual encyclopedia in which specialized cells fire in response to a very particular type of stimulus

Parallel processing - the brain’s natural processing of vision

• we simultaneously process many different aspects of a stimulus
  • damage to parts of our visual network can disrupt this allowing some processing to happen but stopping others
• blindsight - a phenomenon when a person is critically blind but can perceive motion

Color vision

• Young-Helmholtz Trichromatic theory - the cones are sensitive to either red, green, or blue and combinations of these allow us to see color
  • people with color blindness may have monochromatic or dichromatic vision
• Opponent-Process theory - says we have three opponent color pairs
  • red/green, yellow/blue, black/white
  • color vision comes from neurons being turned on or off by these colors

Perceptual constancy - when our brains perceive objects as having consistency (form, color) even when visual input differs

• Color constancy - we perceive objects (especially familiar ones) as having consistent color, even if conditions alter the wavelength being reflected by the object
• our vision is also good at shape and size constancies

McGurk effect - when our sense of vision and hearing conflict with each other, vision wins