Sensation and perception

• Sensation


  The activation of receptors in the various sense organs
• Sensory receptors


  Specialized forms of neurons stimulated by different kinds of energy rather than by neurotransmitters
• Sense organs


  • Eyes
  • Ears
  • Nose
  • Skin
  • Taste buds
• Transduction


  Turning outside stimuli into neural activity
• Just noticeable difference (jnd or the difference threshold)


  The smallest difference between 2 stimuli that is detectable 50 percent of the time
• Absolute threshold


  The smallest amount of energy needed for a person to consciously detect a stimulus 50 percent of the time it is present
• Subliminal stimuli


  Stimuli that are below the level of conscious awareness, just strong enough to activate the sensory receptors, but not strong enough for people to be consciously aware of them
• Subliminal perception


  The process by which subliminal stimuli act upon the unconscious mind, influencing behavior
• Subliminal messages and perception are linked to the idea of mind control, and the roots of this are placed very far back in our history. Mind control is where an individual or group of individuals can be controlled without their awareness. It is perception below the individual's/group's threshold. It is also the idea that people can be made to do things they would not ordinarily do
• Habituation


  The tendency of the brain to stop attending to constant, unchanging information
• Sensory adaptation


  The tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging
• Brightness


  Determined by the amplitude of the wave - how high or how low the wave actually is
• Color (hue)


  Determined by the length of the wave
• Saturation


  The purity of the color people see
• Cornea


  • Clear membrane that covers the surface of the eye, protects the eye, focuses most of the light coming into the eye

  
• Aqueous humor


  • Clear, watery fluid that is continually replenished, supplies nourishment to the eye
• Pupil


  • Hole through which light from the visual image enters the interior of the eye
• Iris


  • Round muscle (the colored part of the eye) in which the pupil is located, can change the size of the pupil, helps focus the image

  
• Lens


  • Clear structure behind the iris, suspended by muscles, finishes the focusing process begun by the cornea
• Visual accommodation


  The change in the thickness of the lens as the eye focuses on objects that are far away or close
• Vitreous humor


  • Jelly-like fluid that also nourishes the eye and gives it shape
• Nearsightedness (myopia)


  The shape of the eye causes the focal point to fall short of the retina

  
• Farsightedness (hyperopia)


  The focus point is behind the retina
• Retina layers


  • Ganglion cells
  • Bipolar cells
  • Photoreceptors that respond to various light waves
• Rods


  • Visual sensory receptors found at the back of the retina, responsible for noncolor sensitivity to low levels of light
• Cones


  • Visual sensory receptors found at the back of the retina, responsible for color vision and sharpness of vision
• Blind spot


  Area in the retina where the axons of the three layers of retinal cells exit the eye to form the optic nerve, insensitive to light
• Dark adaptation


  The recovery of the eye's sensitivity to visual stimuli in darkness after exposure to bright lights
• Light adaptation


  The recovery of the eye's sensitivity to visual stimuli in light after exposure to darkness
• Trichromatic theory


  Theory of color vision that proposes three types of cones: red, blue, and green

  
• Opponent-process theory


  Theory of color vision that proposes four primary colors with cones arranged in pairs: red and green, blue and yellow

  
• Monochrome colorblindness


  A condition in which a person's eyes either have no cones or have cones that are not working at all

  
• Red-green colorblindness


  Either the red or the green cones are not working
• Sex-linked inheritance


  The gene for color-deficient vision is recessive

  
• Wavelength


  Interpreted as frequency or pitch (high, medium, or low)
• Amplitude


  Interpreted as volume (how soft or loud a sound is)
• Purity


  Interpreted as timbre (a richness in the tone of the sound)
• Hertz (Hz)


  Cycles or waves per second, a measurement of frequency
• Auditory canal


  • Short tunnel that runs from the pinna to the eardrum (tympanic membrane)

  
• Eardrum


  • Thin section of skin that tightly covers the opening into the middle part of the ear, when sound waves hit it, it vibrates and causes three tiny bones in the middle ear to vibrate