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The SensesOur SENSES tell us:
• What is out in the environment?
• How much is out there?
• Is there more or less of it than before?
• Where is it?
• Is it changing in time or place? Other
senses?
Each of the senses uses specialized receptors to detect relevant incoming stimuli.
Sense Receptors in Humans
TouchTasteHearingVision Smell
Meissner’sCorpuscle
Freenerve ending
Rod Cone
The Senses• Everyone is their own
laboratory with which to test the senses.
• Non-human animals are sensitive to different “energies” in the environment.
Energy as Information
Forms of energy that can affect cellular processes and thus stimulate sensory systems:• Mechanical (touch, pressure, stretch)• Electromagnetic (light, magnetic, electrical)• Chemical (smell, taste)
Vision – The Eye
Many Different Kinds of Eyes
• Different types of structures to detect light
• Distinctive views of the world needed for survival.
Differences in Visible Wavelengths
Ultraviolet
Insects that feed on flowers, such as bees, have eyes that also can detect ultraviolet
Electromagnetic Spectrum
UltravioletUltraviolet
Because bees help pollinate them, flowers display ultraviolet markings that attract and guide the bee to the pollen.
http://www.dailymail.co.uk/pages/live/articles/technology/technology.html?in_article_id=473897
InfraredInfraredHeat (infrared) has longer wavelengths
Electromagnetic Spectrum
Vision – The Eye
Vision – The Eye
2.5 cm;7 g
Vision – The Eye
?
Lens
Retina
?
Vision – The Eye
Vision – The Eye
Rods: most sensitive to light and dark changes, shape and movement and contain only one type of light-sensitive pigment.
- not good for color vision. - more numerous than cones in the periphery of the retina.- 120 million rods in the human retina.
Cones: are not as sensitive to light as the rods. - cones are most sensitive to one of three different colors (green, red or blue); perception of color; work in bright light. - fine details. - 6 million cones in the human retina.
ColorCards
Vision – The Eye
Vision – The Eye
Location of Rods vs Cones?
++
Movement?Color?Detail?
3
Vision – The EyeIshihara Colorblindness Tests
Vision – The Eye
Optic Disk – no photoreceptors!
Vision – The Brain
Right Left
Left Right
Vision – The Brain
Path that visual information takes in the brain
Primary visual cortex
Color area
Number appearance area
Ramachandran, V.S. and Hubbard Ed (2003), Hearing Colors, Tasting Shapes, Scientific American, Vol 288 Issue 5 (May 2003), 42-49.
Do your eyes fool your brain?
Color Aftereffects
Adaptation
Do your eyes fool your brain?
Do your eyes fool your brain?
Do your eyes fool your brain?
Do your eyes fool your brain?
Do you see a triangle?
Do your eyes fool your brain?
A
B
C
Which line does “A”
match up with?
It depends on how you look at it!
It depends on how you look at it!
Why Do We Have 2 Eyes?
Advantages/disadvantages of eye placement?
Blind spot?Depth Perception?Predator vs. Prey
Why Do We Have 2 Eyes?
Overlapping visual field
Depth PerceptionMonocular/binocular cues?
Relative size
Interposition
Linear perspective
Aerial perspective
Light and shade
Monocular movement parallax
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