© west educational publishing sensation and perception c hapter 4 s ensation and perception form...

© West Educational Publishing

Sensation and Perception

CHAPTER 4Sensation and perception form our world. Sensation is processed by physical receptors; perception is a psychological function of interpretation.

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Sensory Processes

Sensation

Perception

Sensation is the process of receiving information from the environment through remarkable receptors in the human body.

Perception is the psychological process of organizing sensory information to make it meaningful.

These two processes are intermixed.

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The body receives information through the five main senses.

The Five Human SensesHearing

Vision Taste

Smell

TouchEXIT

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An absolute threshold is the minimal amount of sensory stimulation needed for a sensation to occur.

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Vision is the dominant sense.

Iris

Pupil

Cornea

Retina

Blind Spot

Click on the arrows for more information.

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The Iris

The iris is a muscle that opens and closes in order to control the amount of light entering the eye.

Iris

Iris Pupil

Cornea

Retina

Blind spot

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The CorneaThe cornea is the outer covering of the eye.

Cornea

Iris Pupil

Cornea

Retina

Blind spot

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The Pupil

The pupil is the opening in the eye.

Pupil

Iris Pupil

Cornea

Retina

Blind spot

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The RetinaThe retina is the back of the eye that has receptors for light.

Retina

Iris Pupil

Cornea

Retina

Blind spot

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The Blind Spot

The blind spot is where the optic nerve exits and there are no receptors for light waves.

Blind Spot

Iris Pupil

Cornea

Retina

Blind spot

Click for more information.

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Close your left eye and stare at the dot and move either forward or backward until the cube disappears.

Blind Spot Demonstration

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Rods Rods are visual receptors that “see” only black and white and are most sensitive in low light.

ConesCones are visual receptors that receive color and are most sensitive in daylight.

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How many?

Where concentrated?

Sensitive to light?

Sensitive to color?

Rods

120-125 million

Very sensitive

No

Periphery of retina

Cones

7-8 million

Center of retina

Low sensitivity

Yes

Rods and Cones

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Color Vision

Some people cannot tell the difference between certain colors. The most common form is the inability to see the colors of red or green.

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CochleaThis structure is a snail-shaped part of the ear that hastiny hairs and fluid that vibrate with incoming sound.

EardrumThis is a piece of skin stretched over the entrance to the ear and vibrates to sound.

The Structure of the Ear

CochleaEardrum

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Sound

Audition

Sound is energy; it travels in waves like light, but much slower.

Characteristics

Pitch: how high or low a sound is

Timbre: complexity of tone

Intensity: loudness (measured in decibels)

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Cutaneous Senses (Touch)

There are 3 types of receptors:

for pressure

for temperature

for injury or poison

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Smell (Olfaction)

The sense of smell performs a critical role in providing information about the food we eat. It is very closely related to the sense of taste.

Animals also use smell (chemicals called pheromones) to communicate sexual interest.

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Taste

Taste receptors on the tongue are called taste buds.

There are four types of taste receptors: salty, sweet, sour, and bitter.

These receptors combine sensations to create subtle flavors.

Salty

SweetSour

Bitter

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Perception

Size constancy: ability to remember the size of an object no matter where it is located

Color constancy: ability to perceive an object as the same color regardless of the environment

Shape constancy: ability to perceive an object as having the same shape regardless of the angle

Space constancy: ability to judge distance by perceiving either self or object movement

Perceptual constancies use memory to maintain order in the world.

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Perceptual Organization

Gestalt: making incomplete organization whole (they way something should be rather than how it actually is)

Similarity: grouping like things together

Proximity: grouping things together that are near each other

Closure: filling in the missing details

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Closure Proximity

Similarity

Perceptual Organization

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Perceptual Illusions

Franz Müller-Lyer designed this illusion in 1889.

Illusions are misperceptions. They illustrate how we organize objects into meaningful perceptions .

Which line is longer?EXIT

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The Vertical-Horizontal Illusion

Are the two lines the same length?EXIT

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In the figure-ground illusion, the figure is in the front while the ground is in the back. Do you see the faces facing one another or do you see the vase?

Figure-Ground Illusion

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Click the forward arrow to move the cylinder on the right forward to the middle cylinder.

Which cylinder is largest?

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Which cylinder is largest?

Now click the forward arrow to move the cylinder forward to the front cylinder.

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Which cylinder is largest?

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Summary of Main Topics Covered

Sensory Processes

Perception

•Vision•Hearing•Touch•Smell•Taste

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