• Goals
  • What is the difference between sensation and perception?
  • How are we able to build a world of color and form?
• A few definitions...
  • Sensation - the process by which we receive and represent physical energy from our environment
  • Perception - the process of organizing and interpreting sensory information. Through this process we recognize meaningful objects and events
• Processing Information
  • Together, sensation & perception help us to make sense of the world
  • Bottom-up processing - analysis that begins with the sense receptors and works up to the brain's integration of sensory information
  • Top-down processing - processing guided by higher-level mental processes. We construct perceptions drawing on our experience and expectations
• Thresholds: Awareness of Stimuli
  • Absolute thresholds - the minimum stimulation necessary to detect a particular stimulus 50 % of the time
  • However, the absolute threshold changes according to the perceiver's experience, expectations, motivation, and level of fatigue
• Noticing Differences
  • We need to be able to detect important stimuli in our environment, but we also need to detect small differences between stimuli
  • Difference threshold - minimum difference a person can detect between 2 stimuli 50% pf the time
  • Weber's law - the difference threshold is not constant, but is a constant proportion of the stimulus
• Changing and Unchanging Stimuli

  • Selective Attention &endash; the focus of our conscious awareness on a particular stimulus
  • Our everyday world is filled with many stimuli, we can't pay attention to everything!
  • Coctail party effect

  • Sensory Adaptation &endash; we become less sensitive to an unchanging stimulus
    • Our sensory receptors are attentive to new stimuli
    • This allows us to pay attention to informative changes in our environment
• Vision: How Do We Perceive the World?
  • We don't actually "see" colors, we instead see electromagnetic wavelengths that our brain interprets as light
  • Hue/Color is determined by the light's wavelength (distance between two wave peaks)
  • Intensity (or brightness) is determined by the amplitude of the light wave (or the amount of energy in the light wave)
• The Path of LightÉ
  • Pupil --> Lens --> Retina
• At the retina
  • First hits the outer layer of cells
  • Rods &endash; black, white, and gray. Located on the peripheral retina. Low light and twilight conditions
  • Cones &endash; color and fine detail. These are concentrated at the fovea. Well-lit conditions and daylight
  • Generate neural signals that activate bipolar cells which activate ganglion cells.
  • The axons of ganglion cells form the optic nerve, which carries the information to your brain
  • Know the parts of the eye and retina
• Processing Visual Information
  • The retina actually processes some info. However, most info is processed in the occipital lobe.
  • Eye --> optic nerve --> optic chiasm --> visual cortex of occipital lobe
  • Cells in the visual cortex are feature detectors. They respond to a particular feature, such as edges, lines, angles, & movement
  • This info is passed to the temporal & parietal cortex, which includes brain cells that respond to visual scenes
• Young-Helmholtz Trichromatic Theory
  • The retina has three types of color receptors, sensitive to red, green, and blue. Combinations of these colors produce the different hues. This is an additive process.
  • Explains some types of colorblindness
  • Does not account for the afterimage effect and the fact that some colors appear to be linked
  • Color-Deficient Vision
• Opponent-Process Theory
  • Once this info leaves the receptors in the retina, visual information is analyzed in terms of the opponent colors (green vs. red; blue vs. yellow; black vs. white).
  • Increased activation of one type of color cell decreases activation of another
  • This occurs before the information is passed to the visual cortex.
• Hearing Sounds
  • Our ears detect sounds waves which generate nerve impulses that we interpret as sound
  • The frequency (length of the wave) determines the pitch. Longer waves = lower pitch. Shorter waves = higher pitch
  • The amplitude of the wave (height of the wave) determines the loudness. Big amplitude = louder noise, small amplitude = softer noise
• Changing Sound Waves to Neural Impulses
  • Outer ear --> eardrum --> middle ear --> inner ear
  • Middle ear (hammer, anvil, and stirrup)
    • concentrates the vibrations received from the eardrum
  • Inner ear (cochlea)
    • a coiled, bony, fluid filled tube
    • sounds waves are converted into neural impulses
  • know parts of the ear mentioned here
• How are we able to determine pitch?
  • It's determined by frequency, right? Yes, but...
  • Place theory - different pitches trigger activity at different points of the basilar membrane of the cochlea
  • Frequency theory - the entire membrane vibrates, triggering neural impulses at the same rate as the sound wave
  • Which theory works bests?
    • Like vision, the theories work together
    • Frequency theory, doesn't explain how we hear high pitched sounds, because some sound waves have a frequency that's faster than particular sound waves
    • Above 4000 Hz, place theory is a better explanation
• Locating Sounds
  • Why do we have two ears?
  • We can detect the location of noise because sounds reach our ears at different times.
  • This is why it is difficult to pinpoint sounds if they are coming from an equidistant location form our ears (in front, behind, directly over...)
• How do we loose our ability to hear?
  • Conduction hearing loss - occurs when there are problems with the mechanical system that conducts sound waves.
  • Sensorineural hearing loss - occurs when the cochlea's hair cell receptors are damaged
    • Long term exposure to 80 dB causes potential hearing loss (see chart in text for ex.)
    • Even short term exposure to sounds above the pain threshold (gun firing at close range) can cause permanent damage
• Touch
  • We seem to be receptive to 4 sensations:
    • pressure, warmth, cold, and pain
  • All other skin sensations are combinations of the four basic sensations
    • Determining temperature
• Pain
  • Pain is adaptive! It tells us that something is not right!
  • Gate-control theory - the spinal cord either blocks pain signal that go to the brain, or allows them to go through. The "gate" is closed when there is activity in the large nerve fibers, or by the brain itself
  • Endorphins & placebo effect
  • Phantom limb phenomena
  • Pain fibers HAVE BEEN IDENTIFIED
• Taste
  • The structuralists found that taste is composed of 4 sensations
    • sweet, sour, salty, and bitter
  • Chemical sense. Taste buds catch food chemicals.
  • However, taste is also affected by smell.
  • Sensory interaction - one sense influences another
• Smell
  • This is also a chemical sense. Olfactory receptor cells respond to particular odors and send signals straight to the:
    • olfactory bulb (process sensory info.)
    • Amygdala (emotional reaction)
    • Hippocampus (elicit & form memories)
  • Unfortunately, how the receptors work is unknown
    • no elemental odors
    • no parallel system to other senses
    • receptors seem to work in combination
• Pheremones
  • Vomeronasal organ (VNO)
    • Responds to invisible, odorless molecules
    • In humans and animals
  • T-shirt study
  • How much does this determine our behavior?
    • Perfume/cologne
    • Birth control pills
• How do we monitor our own position in space?
  • Kinesthesis - our body's system for knowing where our individual body parts are
  • Vestibular sense - the sense of the body movement and position. Includes sense of balance
• Know from text alone:
  • Key terms and main concepts (pages 128-136)
    • Perceptual organization
    • Perceptual constancies
    • Perceiving distance & depth
  • Visual illusions fun to look at

Review Session Sun 6:30-9:30pm in Rm 338 of the Psyc Bldg