Chapter 4. Absolute Threshold – level of sensory stimulation necessary for sensation to occur ◦...
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Transcript of Chapter 4. Absolute Threshold – level of sensory stimulation necessary for sensation to occur ◦...
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Sensation and Perception
Chapter 4
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Absolute Threshold – level of sensory stimulation necessary for sensation to occur◦ We do not pay attention to small sounds or
background noise if it is not important to us Sensation – process of receiving
information Perception – make it meaningful
Sensory Processes
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Vision◦ Dominates the human senses◦ Lights starts out as white light and color is seen
only after the waves of white light hits objects and bounces back at us at different speeds or frequencies
Sensation
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The Cornea and Iris ◦ The cornea is the shiny fluid in your eye
that covers your eye◦ The iris is a colored circular muscle that
opens and closes into larger or smaller circles to control the amount of light getting into the eye
Sensation
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Lens◦ Focus objects you see onto the back of the
eye Pupil
◦ Light changes the size of your pupil◦ If you are disgusted your pupil will get smaller or
if you like something they will get larger◦ Pupils also open completely if someone is afraid
Sensation
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Retina◦ When light that enters the eye gets to the back of
the eyeball it hits the retina Rods and Cones
◦ Rods are very sensitive to the violet-purple range of wave lengths
◦ Cones are used for color and daylight vision
Sensation
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Color Defects◦ 8% of males and .5% of females have some
type of color blindness ◦ Truly “color blind” people are very rare◦ Animals have very elaborate rod and cones
systems Bulls get enraged by a red flag because of its color is
a myth
Sensation
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Afterimages ◦ If you stare at a colored object for a minute the
chemicals in the cones for the colors you are seeing will be partially used up
◦ Afterimages occur from the remained unused cones
Sensation
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Hearing Sound waves have a slower range of
speed than light waves Bats can find food at night by bouncing
sound waves off of them
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Characteristics of Sound◦ Sounds vary in
pitch and intensity Intensity is
measured in decibels 130 Decibels and
beyond can become painful
Hearing
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The Structure of the Ear◦ Ear size makes very little difference in what you
can hear◦ Sound waves are funneled in the ear
towards the eardrum When sound waves hit the drum it vibrates all
the way to the cochlea Key to hearing is in the cochlea by the cilia (hair like
extensions) Sends message to the auditory nerve in the brain
where the sound is interpreted
Hearing
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Our skin contains three types of receptors◦ Pressure
Registers a pinprick, bruise, ant crawling up your arm◦ Changes in Temperature◦ Remains active continuously to record an
injury or poison Causes the painful feelings we have
Touch
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Olfaction depends on the ability to detect chemicals
We come in second to animals in smelling Odors are hard to define using words but if
it is associated with an emotional event we never forget it
Smell Communication ◦ Smell is more important in eating than taste
Smell
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Taste receptors operate by chemical communication
Mucus and Saliva cleanse the buds 4 Types of receptors
◦ Salt, Sweet, Sour, and Bitter
Taste
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Salt ◦ Salt is necessary for survival ◦ Desire for salt gradually tapers off with age but
can reappear much later in life Sugar
◦ Vital for energy to run the body Sour and Bitterness
◦ Sourness detection serves as a protective function
◦ Food that has gone bad has a sour taste to it – but we usually smell it before we eat it
Taste
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Perception is a matter of interpretation and expectation
Depth Perception◦ Visual Cliff Experiment
Experimenter was at the Grand Canyon and wondered if babies would crawl past the canyon rim
Lab – used a large table with retaining walls made of wood on the sides and a clear sheet of Plexiglas that made it appear there was a drop off
The mothers encouraged their children to go across the “drop” but the babies refused
Perception
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Retinal Disparity ◦ Difference between the images received by
each of your retinas Example: Hold one finger in front of your face and
close one eye – now close the other What happened to your finger
Perception
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Gestalt Psychologists used certain perceptual cues to make sense of items◦ Proximity – how close things are to one another◦ Closure – Fill in details that are not part of the
picture
Perception
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Perception Illusions
◦ Occur when we perceive something inaccurately
◦ Come from the need for us to make sense of our surroundings
◦ Reversible Figure – The eye-brain mechanism keeps changing its mind
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