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Sensation and Perception. Chapter 4. Sensory Processes . 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
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Sensation and Perception Chapter 4
Sensory Processes • 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
Sensation • 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 • 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 • 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 • 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 • 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 • 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
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
Hearing • Characteristics of Sound • Sounds vary in pitch and intensity • Intensity is measured in decibels • 130 Decibels and beyond can become painful
Hearing • 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
Touch • 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
Smell • 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
Taste • Taste receptors operate by chemical communication • Mucus and Saliva cleanse the buds • 4 Types of receptors • Salt, Sweet, Sour, and Bitter
Taste • 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
Perception • 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 • 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 • 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 • 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