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Sensory Systems

Sensory Systems. Gustav Fechner 1801-1887. Studied brightness, light and afterimages by looking directly at the sun (Bad Idea!) Noted for defining absolute threshold and difference threshold

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Sensory Systems

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  1. Sensory Systems Gustav Fechner 1801-1887 • Studied brightness, light and afterimages by looking directly at the sun (Bad Idea!) • Noted for defining absolute threshold and difference threshold • founder of psychophysics (concerned with the effect of physical processes on the mental processes and of an organism

  2. A closer look at the Vision • http://education-portal.com/academy/lesson/how-does-vision-work.html#lesson Blue Man Group: Rods & Coneshttp://www.youtube.com/watch?v=W-yLfm5HsHc

  3. Optical Illusions

  4. Contrast Effects • Hermann Grid • In addition to the pattern of black boxes, we see black dots in the intersections of the white lines. • This phenomenon is called a contrast effect • due to the way in which light contrasts are interpreted by our eyes

  5. Geometric Illusions http://opticaleffect.tripod.com/hering_illusion1.htm The concentric squares are, in fact, parallel, but the diagonal lines in the background make them appear slanted and crooked.  This illusion also exhibits some aspects of contrast effects, as the boxes around the edge seem to pop out. The red/pink lines are parallel in the image above.  However, they appear to bend or bulge outward due to the rays extending from the center.  This is known as the standard Herring illusion (dating to 1861).

  6. Which line is longer? In the Muller-Lyer illusion, both horizontal lines are the same length but the orientation of the "arrows" makes the bottom one seem longer than the top one.

  7. in the Judd illusion the orientation of the "arrow" on each end causes the midpoint (as marked) to appear off-center. 

  8. The first (left) one appears to bulge out and the second (right) one seems to ripple like a flag or waves, when in fact both are normal checkerboards.

  9.   In the images above there are three partial shapes (either circles or squares).  They are oriented, however, such that their cut out portions appear to frame another shape (either a square or a triangle). 

  10. Illusions of Structure and Form We immediately recognize this as an elephant and at first see nothing wrong with it...only to realize that something indeed is quite wrong!  The Gestalt laws of "good form" come to bear here: we know an elephant and recognize it pre-consciously without analyzing the image of it.

  11. Look at the cube below and pay particular attention to the brown cell in the middle of each side. How do they compare? Do they all look like the same shade of brown??

  12. Now look at the "masked" version of the same image below, in which the neighboring cells are darkened and ignored by the visual system. Notice: the brown cells are the same color.

  13. Here is another similar example in which the dotted central tile is actually the same color: As with the cube, this is because the neighboring colored tile influence our perception of the color of the center tile: it is seen as "bluer and lighter" next to reds and brown and is seen as "browner" next to "greener" greens and more blue (right).   In other words, the nearby tiles weight the ratio of cone responses and therefore different colors are perceived! 

  14. If you take a look at the following  picture , it looks animated…it’s not!  Your eyes are making it move.  To test this, stare at one spot for a couple seconds and everything will stop moving.  Or look at the black center of each circle and it will stop moving.  But move your eyes to the next black center and the previous will move after you take your eyes away from it....   

  15. Which circle in the middle is bigger?

  16. You should see a man's face and also a word...Hint: Try tilting your head to the right, the world begins with 'L'

  17. Color Deficiencies • See photos on page 132 of book • Previously called color blindness = Cones contain only 2 of the 3 possible color sensitive pigments

  18. Audition http://education-portal.com/academy/lesson/mechanics-of-hearing.html#lesson • Audition • the sense of hearing • Frequency • the number of complete wavelengths that pass a point in a given time • Pitch • a tone’s highness or lowness • depends on frequency

  19. Backmasking: • http://jeffmilner.com/backmasking/ • Mental set = predisposition to perceive something • Listen w/o subtitles • Listen with subtitles = “perceptual set” • brain is focused on relating the sounds with the words • Brain expects the words to match the sounds • kjadklfj

  20. The Intensity of Some Common Sounds

  21. Audition • Deafness- May be caused bytumors, skull injury, poison, birth trauma, rubella • Conduction Hearing Loss • hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea • Nerve Hearing Loss • hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve

  22. The Chemical Senses: Taste and Smell http://education-portal.com/academy/lesson/taste-touch-and-smell.html#lesson Olfaction = detects airborne chemicals Gustation = detects chemicals through receptors in mouth

  23. Gustation • Taste cells are chemical sensitive receptors located in taste bud clusters • Taste buds are located on the bumps on your tongue

  24. Basic qualities of taste: Sweet Sour Salty Bitter Umami Other influences may be smell, temperature or “touch”/texture Sensory Interaction the principle that one sense may influence another as when the smell of food influences its taste

  25. Receptors for smell are located on the olfactory patch which is a thin membrane in the upper nasal cavity • Olfactory cells are stimulated by gases dissolved in the fluid covering the membrane • For stimulus to be “smelled,” it must be dissolved Olfaction

  26. Skin Senses • Body’s largest sense receptor system • Receptors for this system are located throughout the body

  27. Sensation of pain requires not only that pain information from skin receptors be active, but also the neural gate in the spinal cord to allow these signals to pass to the brain (the gate is closed when critical fibers in the spinal cord are activated) • Pressure stimulation tends to close the neural gate (activate the critical fibers) which is why rubbing a hurt area may relieve pain temporarily. Gate Control Theory (Melzak)

  28. Kinesthesis • Communicates information about movement and location of body parts • Receptors found in joints, muscles and ligaments

  29. Vestibular Sense • Equilibratory sense • Knowledge of body position as in sense of balance • Receptors in semicircle canals (rotating movement) and vestibular sacs (straight line movement) in inner ear

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