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 Pupil Focus objects you see onto the back of the eye 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 Rods and Cones 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 Sugar Sour and Bitterness 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