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AP Sensation & Perception

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AP Sensation & Perception. What is the difference?. Sensation: The ability to receive stimuli from the outside world. Perception: Your interpretation of the stimuli. Generally speaking, sensation is universal, perception is individual . The Five Major Senses. Vision (sight)

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what is the difference
What is the difference?
  • Sensation: The ability to receive stimuli from the outside world.
  • Perception: Your interpretation of the stimuli.

Generally speaking, sensation is universal, perception is individual

the five major senses
The Five Major Senses
  • Vision (sight)
  • Auditory (Hearing )
  • Olfactory (smell)
  • Gustatory (taste)
  • Tactile (touch)
  • The ability to recognize stimuli depends on whether the amount of stimuli reaches the level of threshold.
  • Absolute threshold: the weakest amount of stimuli necessary for human sensory systems to recognize
  • Just noticeable difference: smallest increase/decrease that a person senses the difference.
  • If the level of a stimulus stays constant, a person’s sensory system will be able to block out (ignore) it.
  • Sensory systems will notice differences in level of stimuli.
  • Focus also plays a role
  • Most studied
  • Humans have the most complex system
  • Humans one of the few of the animal kingdom to see in color
  • Light goes through the pupil, then reaches the lens, which bends the light to the retina
  • The retina contains two types of light receptors:
  • Rods (black/white, peripheral)
  • Cones (color vision: each cone responds to a different primary color)
how do we see in color
How do We See in Color?
  • Two theories combine to explain the process
  • Opponent-process Theory(EwaldHering)

Some color combinations never seen together (blue-yellow)

Overexposure to one color, will create an afterimage of the opposite color

Process of experiencing color is excitatory and inhibitory from a individual neurons

A positive response for one color, will elicit a negative in another


2. Trichromatic (Young-Helmholtz) Theory

Thomas Young proposed that color vision results from the actions of three different receptors.

Proposed this 70 years before the discovery of cones

Further research by Herman von Helmholtz, showed that three different wavelengths of light could be combined to form any visible color in the spectrum

  • Vibrations of air (aka sound waves) are processed by the auditory system into sounds
  • Sound is funneled into the inner ear from the pinna (outer ear) to the eardrum, which causes the ear bones to vibrate against the cochlea. The fluid in the cochlea is sensed by tiny hairs (cilia), that send a signal to the auditory nerve which is transmitted to the brain
  • Sound waves have two separate elements:
  • Height (amplitude): determines volume
  • Amount (frequency): determines pitch

Volume is measured in decibels

See figure on p. 220

auditory deficiencies
Auditory Deficiencies
  • Deafness: The inability to hear


  • Conduction: middle ear bones become rigid. Hearing aids can help
  • Sensorineural: due to damage to the inner ear. Can be helped with a cochlear implant.
  • Environmental (aka “notch”): Caused by overexposure to loud noise (85 db)
  • Illness/Genetics (e.g. Helen Keller)
  • Tinnitus: Ringing of the ears. The sound is internal. Results from overexposure to loud sounds
  • Approximately 30,000,000 people in the U.S. are deaf/hard of hearing
  • For most people, only two senses work in concert: olfaction and gustatory
  • For a rare few, their sensory systems work in a unique way (e.g. they can feel colors). This phenomena is known as synesthesia.
  • Synesthesia appears to have genetic components (chromosomes 2, 5, 6, and 12:Asher), and may occur in up to 1% of the population
  • May also be connected to autism (Asher)
the chemical senses olfaction and gustation
The Chemical Senses:Olfaction and Gustation
  • Olfaction: The sense of smell

Asnomia: inability to smell

Lock and key theory: different receptors receive different odors.

Smell + Taste = Flavor

  • Gustation : sense of taste
  • Contrary to long-standing theory, taste buds are located throughout the tongue
  • Six basic tastes: Sweet, salty, bitter, sour, umami, fat
  • What about spicy food?
  • Supertasters
tactile and minor senses
Tactile and Minor Senses
  • The largest body organ:
  • Four different types of receptors: pain, pressure, heat, cold
  • Vestibular
  • Kinesthetic
issues in perception
Issues in Perception
  • Perception is learned, and is based on the individual’s interpretation of the sensation.
  • New sensations are compared to ones experienced in the past, which is called frame of reference
  • Subliminal perception: Being able to perceive stimuli below the known conscious threshold (limen). Use of this in advertising is controversial and illegal in the U.S.
illusions and hallucinations
Illusions and Hallucinations
  • Illusion: Mistakes in perception based on real stimuli

Examples: FDR, magic

  • Hallucinations: Mistakes in perception based on imaginary stimuli.

Examples: LSD, delirium tremens

  • Extrasensory Perception (ESP): The ability to receive stimuli outside the normal sensory system.
  • Does it exist?