1. What is it like to live without 1 or 2 of
your basic senses?
Helen Anne
Keller Sullivan
Video Clip – Cochlear Implant

2. What Is
Sensation?
There are 6 - 8 Sensory Systems
None of these are paranormal. (Ex- ESP)
The Basic Five were:
Vision, Hearing, Taste, Smell, and Touch
Added to the Basic 5 are:
Balance, Kinesthetic (sense of weight,
strain, and position of joints & muscles in
space) and Pain. (blocking pain video clip)

3. Sensory Thresholds
Sensation & Perception:
The Basics
Sensation – information which
we receive from the the
environment

4. The Basics
Perception – the process through
which we interpret sensory
stimulation.
Perception Reflects
• Learning
• Expectations
• Attitudes

5. Psychophysics
The study of the relationship
between the perceived magnitude
(strength) of a stimulus versus the
physical magnitude of the
stimulus. (measurable)

6. • Threshold - The minimal values of
sensory stimulation needed to
trigger a reaction
• Absolute Threshold – stimulus
value which is detectable 50% of
the time.
• Difference Threshold – The
smallest change in stimulation
you can detect.

7. VISION

8. LIGHT
 Electromagnetic energy described in
wavelengths
 Main colors of the spectrum:
ROYGBIV

10. PUPIL
 Dark center in middle of iris
 Pupil determines how much light is
let into the eye.
 Changes sizes to accommodate
amount of light available.

11. LENS
 Transparent structure inside eye
 Focuses light rays onto retina.
 Adjusts to the distance of objects by
changing its thickness (squint)
Eye Cataract

12. RETINA
 Neurons (Nerve layer) lining back of eye.
 Retina senses light and creates
impulses sent through optic nerve to
the brain.
 Contains (photoreceptors) that process
visual stimuli
 Photoreceptors = rods, cones

13. Macula

14. OTHER
 Macula -- a small area in the retina that
contains special light-sensitive cells. The
macula allows us to see fine details clearly.
 Vitreous -- the clear, jelly-like substance
that fills the middle of the eye.

15. BLIND SPOT
 Part of retina containing no photoreceptors.
 This is where Optic Nerve leaves the eye
A Baby’s Brain and Vision

16. RODS & CONES
 Rods – respond to varying degrees of light &
dark; night vision; black & white
 More Rods than Cones
 @95% - > 120-125 million
 Cones – mainly color vision
 Function in low light, white,
black, gray. Detects
movement.
 @5% (@ 5 - 10 million

17. RODS & CONES (2)
 Cones
 Cones - thick + tapered
 Bright light, Movement, Whites, Blacks
 Fovea -- Center of eye w/only cones
(@100,000) See in colors.

Visual Acuity or sharpness of sight.
http://escience.anu.edu.au/lecture/cg/Color/theFovea.en.html

18. RODS & CONES (3)
3 Types of Cones
 Respond to Various
wavelengths of color spectrum
 Eyes most sensitive to Green/
Yellow under equal intensity of
light.

19. 3 Theories of Color Vision
 Trichromatic Theory
 Red,Green & Blue Cones
 Correspond to short, medium, & long
waves of light
 *Explains Color Blindness
 Opponent Process Theory
 Cones Work in Pairs
 Red - Green & Blue - Yellow
 Integrated Theory
 Trichromatic and Opponent Theories
work together at different stages

20. COLOR BLINDNESS
 Partial or total inability to distinguish
color
 Why? absence of, or malfunction in,
the cones
 3 types of Cones
 Each sensitive to portion of light
spectrum--red, blue, and green
 Color perception results from the
simultaneous stimulation of 3 cone
types (trichromat)

21. COLOR BLINDNESS
 “Trichromats” = People who see all
colors (Greek term meaning “three
colors”)
 “Dichromats” = Small number of
people see only two colors and the third
registers as a shade of gray.
 Monochromats = See the world in
only black and white. Occurs in about 1
in every 100,000 men.

22. COLOR BLINDNESS
 Colorblind men were recruited during
WWI as bombardiers b/c they would not
be fooled by camouflage on the ground.

23.  Color blindness - 1
 May be a hereditary condition or caused
by disease of optic nerve or retina.
 Acquired color vision problems affects
only the eye with the disease and may
become progressively worse over time.
 Patients with a color vision defect caused by
disease usually have trouble discriminating
blues and yellows.
 Patients with a color vision defect caused by
disease usually have trouble discriminating
blues and yellows.

24. COLOR BLINDNESS -2
 Inherited color blindness is most common,
affects both eyes, and does not worsen over
time.
 Found in about 8% of males and 0.5% of females.
 These color problems are linked to the X
chromosome and are almost always passed
from a mother to her son..

30. COLOR VISION
 Color Circle/Wheel = shows how
complementary colors appear opposite
one another on a color wheel

31. COLOR VISION
 Afterimage = visual sensation that
occurs after the original stimulus has
been removed

32. -Stare at the eye of the red parrot while you count slowly to 20, then look
immediately at one spot in the empty bird cage. The faint, ghostly image
of the blue green bird will appear in the cage.

33. -Try the same thing with the green cardinal. A faint magenta
bird will appear in the cage.

36. What Do Animals See?
Animal Vision
Most diurnal (daytime) animals see in color,
while most nocturnal (night) animals don’t —
but even here there are exceptions.

37. When considering whether animals see in color,
one approach is to look to the structure of the
eyes to see if cones are present. Many nocturnal
animals that scientists have studied lack cones,
relying instead on greater numbers of rods for
extended night vision and keener detection of
movement. As an exception to the nocturnal
rule, owls do have cones, leading scientists to
believe these animals see in color. Most species
of primates, birds, cats and dogs also see in
color to some degree.

38. • Humans three sets of cones for
detecting color in different
wavelengths each cone detects a
wide spectrum that overlaps to
create other hues.
• Animals like cats and dogs have
two sets of cones, making them
color-blind to specific colors. They
do, however, have many more
rods than humans, giving them
greater night vision and a keener
ability to detect motion.

39. Dogs can’t distinguish between green and orange
which will both look grayish .
Green and Orange appear as differing shades of
gray to a dog.
Feline (cats) see in color, but they have trouble
distinguishing reds. . .. Reds appear as differing
shades of gray to a cat. It is believed both dogs and
cats see mainly in grays, yellows, and blues
OTHER ANIMALS

40. ADAPTATION
 Dark adaptation = rods & cones become
more sensitive to light
(entering a dark room)
 Light adaptation = r & c become less
sensitive (leaving dark
room into light)

41. VISUAL ACUITY
 Sharpness of vision FOVEA
 Determines the ability to see visual details
 (Eye exam – Snellen chart) near/far sighted
20/20 vision is a measurement of visual acuity.
• Explanation - 20/20 means a person can
see small detail from 20 feet away -- the same
as a person with normal eyesight would see
from 20 feet.

43. • It is possible to
have vision superior
to 20/20:
Maximum acuity of
the human eye
without visual aids
around 20/15 to
20/10.