Chapter 6 Sensation and Perception Sense Organs Sense Organs organs that receive stimuli eyes ears nose mouth Sensory Receptor Cells specialized cells within the sense organs that send skin i e 5 senses neural impulses to the brain Sensation vs Perception Sensation information coming into your brain Perception organizing and interpreting the information what you make of the information Example your ear receives a stimulus in the form of sound waves sensation you perceive that your favorite song is on the radio o Cannot have perception without sensation they go hand in hand Sensory Limits thresholds Absolute Threshold the smallest magnitude of a stimulus that can be detected weakest detectable stimulus i e hear a watch ticking 20 ft away taste a teaspoon of sugar in a gallon of water see a candle flame 30 miles away smell one drop of perfume in a 6 room house feel a wing of a fly dropped on your cheek Difference Threshold the smallest detectable difference between two stimuli o Depends on the original stimulus weber s law applies to difference threshold Weber s Law The Difference Threshold between two things depends on the strength of the original stimulus the stronger the original stimulus the bigger the changes must be in order for them to be noticed yet changes in weak stimuli are very noticeable o Example if holding 100 lbs must add 2 lbs to detect a difference If holding 10 lbs only need to add 2 oz to detect a difference Sensory Adaptation the perceived weakening of a sensation due to prolonged exposure to stimulus o Example when you jump into cold water at first you feel freezing but after a few moments the water does not feel as cold sensory receptors are fatigued and do not detect the stimulus as strong as they first did o Example wear your wedding ring so frequently after a while you no longer feel it on your finger you ve adapted to the ring being a part of your body Vision Must have light to see Light is composed of waves that give us Hue wavelength of light that gives us color Brightness intensity of the light Saturation complexity of the light gives us purer vs paler colors o Human Visual Spectrum ROY G BIV Parts of the Eye Pupil the opening of the iris black part pupil is larger in Cornea protective coating on the surface of the eye Iris the colored part of the eye that regulates the amount of light that enters darkness to let light in and smaller in light retina retina upside down and lens flips it and brain flips it back Retina images fall here sensory receptor cells are here falls on Lens the transparent portion of the eye that focuses light onto the How the Eye Works The retina has two types of receptor cells Rods receptor cells that code information about light and dark located Cones cells that code information about light dark color located at center Fovea spot where most of the cones are concentrated gives us clearest outside the center of the retina 120 million rods in each eye of retina 6 million cones in each eye sharpest image images focused directly onto the fovea are clearest because of the high concentration of cones area where the optic nerve attaches and contains no rods or cones therefore there is a blind spot Optic Nerve the nerve that carries visual neural messages to the brain Color Blindness Most animals only see black white and shades of gray Total color blindness in humans is extremely rare due to lack of cones or Color Blind people can usually see some colors and not others Most common Red Green color blind cannot see see shades of gray instead malfunctioning cones but can see Yellow Blue spectrum Rarer Yellow Blue color blind but can see Red Green spectrum 8 of males are color blind Extremely rare in females Color Vision Trichromatic Theory The first level of color processing o There are three different kinds of cones in the eye and that each respond to light in either 1 Red 2 Blue or 3 Green wavelengths therefore all sensations of colors result from stimulating a combination of these three cones The Opponent Process Theory second level of color processing o In addition to three types of cones one for red blue and green there are opponent process mechanisms which respond to either the red green or the yellow blue wavelengths Color Afterimages After staring at one color for a long time we will see an afterimage of the opposite color Visual Perception How is visual information processed into meaningful perceptions The Figure Ground concept when we see something whatever is the center of our attention is the figure whatever is in the background is the ground we can change our perception of the same image by switching the figure and the ground The 4 Gestalt Principles of Perceptual Organization 1 Proximity things that are close together are grouped together in the mind as 2 Closure incomplete figures tend to be seen as complete because our brain if they belong together fills in missing information 3 Similarity similar things are seen as being related 4 Continuation images are seen in ways that produce smooth continuation Visual Constancy o Brightness Constancy we understand the brightness of an object does not change even when the object is dimly lit o Color Constancy we understand that colors do not change despite different conditions of light o Size Constancy size does not change o Shape Constancy shape does not change Depth Perception Monocular Cues cues in the environment that suggest depth and can be seen by only one eye think linear perspective Binocular Cues Convergence eyes angle inward as an object gets closer to us Retinal Disparity because each retina is a few inches apart they have slightly different images and this helps with depth perception Optical Illusions Illusions are created using mostly monocular depth cues what we perceive is not always reality Examples The Ames Room Pronzo and Muller Lyer illusions use monocular depth cues to trick the eye Sound energy travels in waves Chochlea transfers sound waves into neural impulses Hearing Smell Called olfaction Airborne molecules enter the nose and are transferred to olfactory bulb in the brain for processing Difficult to classify smells Processed directly through the amygdala hypothalamus and hippocampus Smells can often trigger strong emotions memories Taste Called gustation Five basic tastes Sweet Bitter Salty Sour Savory Umami meat or broth Taste buds on the tongue code for taste which is processed in the somatosensory cortex Flavor influences by taste smell and visual cues
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