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The Basic Senses and What They Detect Energy senses • Vision (electromagnetic energy—light waves)

• Hearing (sound waves)

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Chemical senses • Smell (airborne chemical molecules) • Taste (dissolvable chemical molecules)

The skin and body senses • pressure/touch • temperature • pain

• Position (kinesthetic) • Balance (vestibular)

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Sensory Processes There are some basic concepts that psychologists use when talking about the sensitivity of the senses (pages 110 – 114).

• Sensory adaptation: The decline in sensitivity to a

constant stimulus. Therefore, a stronger stimulus is required to activate the sensors.

Why is understanding sensory adaptation important (in what cases would sensory adaptation be “bad”)?

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How do we see?

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Organizing information. You should read the section on rods and cones and organize the information in two columns.

Rods Cones • shape • shape • Approximate number • Approximate number • dark adaptation • dark adaptation • Specialized function • Specialized function • Location/distribution • Location/distribution In addition to this, you should see how this information interrelates with material in the pictures/diagrams and experience (such as the one on page 95).

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The Trichromatic Theory of Color Perception

Cones are responsible for color perception. According to the theory, there are three types of cones in the fovea that are very sensitive to certain wavelengths of light and not very sensitive to the other wavelengths of light.

• Blue light (short wavelength) • Green light (medium wavelength) • Red light (long wavelength)

The perception of other colors (such as yyyeeellllllooowww) is the stimulation of a combination of cones (green and red).

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The Trichromatic Theory of Color Perception What does the trichromatic theory of color perception explain? People with red/green color blindness cannot distinguish between the two colors because their red and green cones are sensitive to the same color. Technically, this should be called color deficiency, but is commonly called being color blind (about 8% for men, and ½% for women).

True color blind people see the world in shades of gray, and are rare (about 1 million people).

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The Opponent Process Theory The trichromatic theory of color perception cannot explain an afterimage such as seeing a faint red, white and blue flag after staring at a yellow/green flag. According to the opponent process theory, there are three types of color sensitive neurons that are sensitive to a certain pair of colors: 1. red / gggrrreeeeeennn red / gggrrreeeeeennn red / gggrrreeeeeennn red / gggrrreeeeeennn 2. blue / yyyeeellllllooowww blue / yyyeeellllllooowww blue / yyyeeellllllooowww blue / yyyeeellllllooowww 3. black / white black / white black / white black / white One single receptor can only be activated to a single color, while the other color is inhibited (blue can be activated, while the yellow is inhibited). With multiple receptors, some receptors can be sensitive to blue, while others can be sensitive to yellow. All color perceptions are a combination of these receptors. For example,

• Orange = red/green + blue/yyyeeellllllooowww • Purple = red/green + blue/yellow

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How does the opponent process theory explain an afterimage?

Afterimages are explained when it is combined with the general principle of sensory adaptation—the weakening of the sensitivity of your senses when they become adapted to a stimulus. When you look at a white piece of paper, it reflects all wavelengths of light. When looking at a yellow/green flag, your receptors are in the following state (I am going to exaggerate) Not very sensitive Sensitive YYYeeellllllooowww / blue GGGrrreeeeeennn / red

Black / white Since the red and blue receptors are sensitive, they will activate and accentuate those colors when you look at a white background, producing a weak afterimage of a red, white and blue flag. Which theory of color perception explains how we perceive color?

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Which theory of color vision is “right”, they both can’t be right?

This is the wrong question to ask about color perception. Both theories explain color perception, but at a different level of color perception. • The trichromatic theory primarily explains perception

within the structure of the eye (the cones and retina) before being transmitted to the brain via the optic nerve.

• The opponent process theory explains perception within the ganglion cells, thalamus and visual cortex.

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Why is understanding the process of color perception important for understanding psychology, science, and perhaps life in general. • No one theory explains complex behavior—it involves

multiple processes. • Sometimes asking the wrong/right question is

important for understanding the world around you. The question that is given to you, may be the “wrong” question.

• Even though they “appear” to be inconsistent, the two theories are consistent. Science needs to be internally consistent

Where will you see this again? • Motivation and Emotion • Personality

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Theories of Sound Perception How do we perceive • low frequency sounds • mid-frequency sounds • high frequency sounds

What are examples of low frequency sounds? What are examples of high frequency sounds? Perception of low frequency sounds (below 500 hertz): • The basilar membrane vibrates at the same frequency

as the sound wave • Therefore, if the sound wave vibrates 300 times per

second (or 300 hertz), the membrane vibrates at 300 times per second.

Perception of high frequency sounds: • Different frequencies cause larger vibrations at different

locations along the basilar membrane. • High frequency sounds cause maximum vibrations

near the stirrup end of the basilar membrane. • Lower frequency sounds cause maximum vibrations

at the other end.

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Conduction deafness: the bones in the middle ear become brittle and have a difficult time amplifying the sound. Hearing aids can help with conduction deafness. Nerve deafness: damage to hair cells in the cochlea. Hearing aids cannot help with nerve deafness.