L5 Ch5A Test Notes Sensation and Perception
Pg. 149 Sensation is the detection of physical energy emitted of reflected by physical objects. Cells in the sense organs- eyes, ears, tongue, nose, skin and internal body tissues detect stimuli. What would happen without sensation? Sound, color, heat, pain.
Perception- set of processes that organize sensory impulses into meaningful patterns. Perception allows us to produce a two-dimensional image on the back of the eye, but we interpret the world in three dimensions.
Pg. 150 Our Sensational Senses Not all scientists agree on the number of senses. The body contains 5 sense organs • Vision (eyes) • Hearing (ears) • Taste (tongue) • Touch (skin) • Smell (nose)
Skin also senses heat, cold, pain. The ear contains receptors that account for balance. All senses evolved to help us survive. What are the benefits of sensing pain? The skeletal muscles account for a sense of bodily movement.
The Riddle of Separate Sensations Sense receptors- cells located in the sense organs. They convert energy of the stimulus into electrical impulses that travel along nerves to the brain.
Pg. 151 Measuring the Senses Absolute Threshold: the smallest amount of energy that can be detected by a person. Reliable detection occurs when a person can detect a signal 50% of the time.
Our senses are very sharp. Normal sensory abilities allow you to: • See a candle flame on a clear night 30 miles away • Hear a ticking watch in a perfectly quiet room 20 feet away • Taste a teaspoon of sugar diluted in 2 gallons of water • Smell a drop of perfume diffused through a 3 room apartment
Pg. 152 Difference Threshold also called just noticeable difference Difference Threshold: the smallest difference in stimulation that a person can detect 50% of the time. Noticeable difference depends on the intensity of the first stimuli. The larger a weight is, the greater the change must be before one can notice the difference. Cola drinkers often cannot tell the difference because the two tastes exceed a person’s difference threshold.
Pg. 153 Signal Detection Theory Signal Detection Theory: Yeasayers-observers, when uncertain, respond “yes” to a given signal. Naysayers- observers, when uncertain, respond “no”, being more cautious and conservative.
Expectations can influence how a person responds to signals. While showering and waiting for an important phone call, you may often think it rang when it did not.
4 kinds of responses are possible to signal: • The person detects a signal that was present (hit) • Says the signal was there when it was not (false alarm) • Fails to detect a signal (miss) • Correctly says the signal was absent when it was not present (correct rejection)
Sensory Adaptation Sensory Adaptation: senses are designed to respond to change and contrast in our environment. You do not feel your watch sitting on your wrist. Adapting to a gas leak would be a problem. Do we completely adapt to extreme stimuli? Such as pain, smell, heat
Pg. 154 Sensory deprivation: absence of normal levels of sensory stimulation. The human brain requires a minimum amount of sensory stimulation in order to function normally.
Pg. Sensory Overload Sensory Overload leads to fatigue and mental confusion. “Cocktail party phenomenon”- blocking out unimportant sounds and focusing only on things of interest.. Important sounds such as your name can be detected.
Pg. 155 Selective Attention Selective Attention: protects us in daily life from being overwhelmed by all the sensory signals
L5 5B Notes Pg. 156Vision More information comes to us through our eyes than any other sense organ.
What We See • Hue- the visual experience specified by color names. Related to wavelength of light; the shorter waves are violet/blue; the longer waves are orange/red • Brightness- the visual experience specified by the amount or intensity of light the object emits or reflects, the more light the object reflects the brighter it appears • Saturation- the visual experience specified by the complexity of light. (vividness or richness of color)
Hue, brightness, and saturation are all psychological dimensions of visual experience
An Eye on the World Cornea- transparent protection Lens- changes shape becoming more or less curved to focus light. Does not function the same as a camera.
Pg. 157 Iris- lets light in by opening/closing; gives the eye its color Pupil- round opening of the eye, contracts during bright light, opens during dim light
Retina- visual receptors in the back of the eye; extension of the brain. When the lens of the eye focuses light on the retina, the result is an upside-down image.
Rods- 120 to 125 million in the retina, more sensitive to light. Enable us to see in dim light and peripheral vision Cones- 7 to 8 million, allows us to see color
Fovea- center of the retina where vision is the sharpest, only contains cones. Dark Adaptation- visual receptors becoming maximally sensitive to dim light. Rods adapt in 20 minutes. Cones adapt quickly in dim light (10 minutes)
Pg. 160 How We See Color TrichromaticTheory- 3 basic types of cones, each responds to different range of wavelengths which give us the experience of blue, green, red
Total Color Blindness- usually occurs when cones of the retina are absent or malfunctioning. Usually a color deficient person is unable to distinguish red from green, so the world is painted in shades of blue, yellow, brown and gray
Opponent- Process Theory- treats pairs of colors as opposing; (red/green, blue/yellow, black/white) http://www.youtube.com/watch?v=BkjfYxOm1ps After-image- cells that switch on or off to signal the presence of one color, send the opposite color when the initial signal is removed.
Pg.161 Constructing the Visual World Pg.162 Gestalt Principles- Study how people organize the world visually into meaningful units and patterns.
Figure/Ground- we always organize the visual field into figure ground. Figure stands out from the rest of the environment. Ground- background of the figure
Proximity- things that are near each other tend to be grouped together • Closure- the brain fills in gaps to perceive complete forms • Similarity- things that are alike in some way tend to be perceived as belonging together. See example in the book pg.163 • Pg.163 continuity- lines and patterns tend to be perceived as continuing in time and space
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Depth and Distance perception Binocular Cues- depth or distance cues that require the use of 2 eyes. (We infer an object’s location by estimating its distance) Convergence- turning inward of the eyes when they focus on a nearby object.
Retinal Disparity- slight difference between what the left eye and right eye sees. Binocular Cues help us estimate distances up to 50 feet. Monocular cues- depth or distance cues that can be used by one eye alone
Interposition- one object blocks a second object, the 1st object is perceived as being closer Linear perspective- 2 parallel lines appear to come together
Visual Constancies: When seeing is Believing Perceptual Constancy- perception of objects as stable • Shape constancy- shape stays constant when our point of view changes • Location constancy- stationary objects remain in the same place • Pg. 164 Size Constancy- an object has constant size as its image becomes smaller or larger
Brightness constancy- an objects brightness stays even though the amount of light the object reflects changes • Pg. 165 Color constancy- objects maintain its hue despite wavelength of light reaching our eyes may change. • Perceptual illusion- misleading perception of reality
Pg. 167 Hearing What We Hear The stimulus for sound is a wave of pressure • Loudness- dimension of auditory experience related to the intensity of a wave’s pressure (Amplitude). The more energy the higher the wave. Measured in units called decibels. Rock concert decibels create immediate danger.