chapter 3: sensation and perception

feature detectors

The ability to detect certain types of stimuli like movement, shape, and angles requires specialized cells in the brain called feature detectors. Without them, it would be difficult to detect a round object, say a baseball, coming at you at 80 mph

depth perception

The ability to perceive the distance of an object and the use of visual cues to perceive the distance or three-dimensional characteristics of objects EX: Walking through school, you can accurately judge the distance of furniture, walls, other people, how far away the board is, and so forth.

middle ear

The part of the ear that amplifies sound waves; consists of three small bones: the hammer, the anvil, and the stirrup.

gate control theory of pain (look up example online)

The theory that pain is a product of both physiological and psychological factors that cause spinal gates to open and relay patterns of intense stimulation to the brain, which perceives them as pain. EX: many professional athletes condition themselves to minimize pain during competitions or tournaments. common techniques like moist heat packs or paraffin baths attempt to relieve pain. A stimulus is applied to the skin and attempts to block the pain signal in the spinal cord from reaching the brain. the experience of pain is also influenced by genetic factors, social and situational factors, and cultural learning experiences about the meaning of pain and how people should react to it.

Retina

a thin, light-sensitive, membrane located at the back of the eye that contains the sensory receptors for vision EX: the retina acts like a movie screen and captures images upside down which is turned rights side up by the brain once processed

rods vs cones

Contained in the retina are rods and cones. Because sensory receptor cells respond to light, they are often called photoreceptors, When exposed to light, the rods and cones undergo a chemical reaction that results in a neural signal. They differ in many ways and as their names imply, rods and cones are shaped differently. Rods: long, thin, have blunt edges, more sensitive to light, rely on for vision in dim light/ at night, adapt relatively slowly to changes in the amount of light reaching max sensitivity to light in ~ 30 minutes Cones: shorter, fatter, one end that tapers to a point, adapt quickly to bright light, reach maximum sensitivity in ~ 5 minutes, sensitive to different wavelengths that produce the sensation of color, require much more light to function effectively, specialized for seeing fine details and vision in bright light The eye contains far more rods (~125 million) than cones (7 million). Once fully adapted to the dark, rods are able to see a thousand times better than cones at detecting weak visual stimuli.

top-down processing

Information processing that emphasizes the importance of the observer's knowledge, expectations, and other cognitive processes in arriving at meaningful perceptions; analysis that moves from the whole to the parts; also called conceptually-driven processing. EX: occurs when we draw on our knowledge, experiences, expectations, and other cognitive processes to arrive at meaningful perceptions, such as people or objects in a particular context. cultural experiences also affect perceptual processes. When looking at a picture, you reach a number of perceptual conclusions about the image.

bottom-up processing

Information processing that emphasizes the importance of the sensory receptors in detecting the basic features of a stimulus in the process of recognizing a whole pattern; analysis that moves from the parts to the whole, also called data-driven processing EX: Imagine trying to assemble a jigsaw puzzle one piece at a time, without knowing what the final picture will be. To accomplish this task, you would work with the individual puzzle pieces to build the image from the "bottom-up" that is, from its constituent parts.

conductive deafness

Occurs when tiny bones of the middle ear are damage or become brittle, as they sometimes do in old age. Can be helped by hearing aide which amplifies sound

accommodation (of eye lens)

The eye lens thins or thickens to bend or focus on incoming light so that the light falls on the retina. If the eyeball is abnormally shaped, the lens may not correctly focus the incoming light on the retina resulting in a visual disorder. EX: in nearsightedness (myopia) distant objects appear blurry because the light reflected off the object focuses in front of the retina. In farsightedness (hyperopia) objects near the eye appear blurry because light reflected off the object is focused behind the retina

opponent-process theory of color vision

The trichromatic theory cannot account for all aspects of color vision. One important phenomenon that the theory does not explain is the afterimage. Afterimages can be explained by the opponent-process theory of color vision, which proposes a different mechanism of color detection from the one set forth in the trichromatic theory. According to the opponent-process theory of color vision, there are four basic colors, which are divided into two pairs of color-sensitive neurons: red-green and blue-yellow. The members of each pair oppose each other. If red is stimulated, green is inhibited; if green is stimulated, red is inhibited. Green and red cannot both be stimulated simultaneously. EX: Red light evokes a response of Red-Yes-Green-No in the red-green opponent pair. Yellow light evokes a response of Blue-No-Yellow-Yes.

sensory adaptation

a gradual decline in sensitivity to a constant stimulus. our experience of sensation is relative to the duration of exposure EX: say your dog gets skunked and you are overcome by the odor of your dog's coat of fur. However, after a few moments, you find that odor is not as pungent anymore and soon longer notice it. This is because your sensory receptor becomes less responsive to a constant stimulus. This is also the reason every family's home has it's own scent that we cannot detect and why we can't detect the smell of our detergent on our clothes-- our sensory receptors have grown accustom to it

fovea

a region in the very center if the retina where most of the cones are concentrated. EX: Focus your eyes on the word for at the beginning of this sentence. In contrast to the sharpness of the letters in For, the words to the left and right are somewhat blurry. The image of the outlying words is striking the peripheral areas of the retina, where rods are more prevalent and there are very few cones.

moon illusion

a visual illusion involving the misperception that the moon is larger when it is on the horizon than when directly overhead. But the moon doesn't shrink as it rises. In fact, the retinal size of the full moon is the same in all positions. People perceive objects on the horizon as farther away than objects that are directly overhead in the sky. The moon on the horizon is perceived as being behind the depth cues, so the depth perception cue of overlap adds to the perception that the moon on the horizon is farther away. The moon illusion also involves the misapplication of the principle of size constancy. Even though the retinal image of the moon remains constant, we perceive the moon as being larger because it seems farther away on the horizon.

Weber's Law

for each sense, the size of a just noticeable difference is a constant proportion of the size of the initial stimulus. Whether we can detect a change in the strength of a stimulus depends on the intensity of the original stimulus. Underscores that our psychological experience of sensation is relative. EX: if you are holding a log (original stimulus) you notice an increase of weight if a second log is placed in your hand. However, if you start out holding a very heavy log (original stimulus) you probably will not detect an increase in weight when the same second log is placed on top of it

Law of Pragnanz (simplicity)

formulated by Gestalt psychologists. the law states that when several perceptual organizations of an assortment of visual elements are possible, the perceptual interpretation that occurs will be the one that produces the "best, simplest, and most stable shape." EX: image 3.16, p117. If following the law of Pragnanz, you organize the elements most cognitively efficient and simple way, perceiving them as three overlapping squares rather than two six-sided objects and one four-sided object

place theory vs frequency theory

frequency theory: The view that different frequencies cause larger vibrations at different locations along the basilar membrane. EX: The sound wave of about 100 hertz would excite each hair cell along the basilar membrane to vibrate 100 times per second and neutral impulses would be sent to the brain at the same rate. There is a limit to how fast neurons can fire-- individual neurons cannot fire faster than ~1000 times per second; yet, we can sense sounds with frequencies higher than 1000 hertz. Hitting a bongo in different spots will produce different sounds -- hitting near the side produces a flatter noise than hitting it in the center place theory: the view that different frequencies cause larger vibrations at different locations along the basilar membrane EX: high-frequency sounds cause maximum vibration near the stirrup end of the basilar membrane. Low-frequency sounds cause maximum vibration at the opposite end. Different pitches excite different hair cells along the basilar membrane. High-pitched sounds are interpreted according to the place where the hair cells are most active. both the frequency theory and place theory are involved in explaining our discrimination of pitch. Frequency theory helps explains our discrimination of low frequencies and place theory helps explain our discrimination of high pitched sounds. Both are involved for intermediate frequencies/midrange pitches

Gestalt Psychology

school of psychology that maintained sensations are actively processed according to consistent perceptual rules, producing meaningful whole perceptions, or gestalts. The Gestalt psychologists emphasized that we perceive whole objects or figures (gestalts) rather than isolated bits and pieces of sensory information. EX: A set of dots outlining the shape of a heart is likely to be perceived as a heart, not as a set of dots. We tend to complete the figure and make it the way it "should" be-- seeing the macro rather than micro

size vs shape constancy

size constancy: the perception of an object as maintaining the same size despite changing images of the retina. When our distance from an object changes, the image of the object that is cast on the retinas of our eyes also changes, yet we still perceive it to be the same size. EX: the red SUV illustrates the perception of size constancy. As the distance between you and the red SUV increased, you could eventually block out the retinal image of the vehicle with your hand, but you don't believe that your hand has suddenly become larger than the SUV. Instead, your brain automatically adjusts your perception of the vehicle's size by combining information about retinal image size and distance shape constancy: the perception of a familiar object as maintaining the same shape regardless of the image produced on the retina EX: Try looking at a familiar object, such as a door, from different angles. Your perception of the door's rectangular shape remains constant despite changes in its retinal image.

cochlea and basilar membrane

the coiled, fluid filled inner ear structure that contains the basilar membrane and hair cells. It is the sense organ that translates sound into nerve impulses to be sent to the brain EX: hair cells in the cochlea are tuned to respond to different sounds based on their pitch or frequency of sounds. People with good hearing can hear and understand speech, even in very noisy rooms. Background noise causes problems for some people's hearing because hearing loss damages not only your hearing, but also your cochleas' ability to filter out background noise. A hearing aid helps amplify noise, but it can't filter out background noise. Some hearing aids have directional microphones, which reduces some background noise, but they as effective as cochleas, since the hearing aids can't get the noise reducing instructions from the brain. as the fluid in the cochlea ripples, the vibration in turn is transmitted to the basilar membrane, which runs the length of the coiled cochlea EX: When a sound wave causes the hair cells to vibrate, the associated neurons become excited. As a result, the sound waves are converted into nerve activity.

subliminal perception

the detection of stimuli that are below the threshold of consciousness perception or awareness. Such stimuli might be rapidly flashed visual images or sounds/odors too faint to be consciously detected EX: The notion that people's behavior could be easily manipulated by subliminal messages first attracted public attention in 1957. James Vicary, a marketing executive, claimed to have increased popcorn and Coco-Cola sales at a New Jersey movie theater by subliminally flashing the words "Eat Popcorn" and "Drink Coke" during the movie.

absolute threshold

the smallest possible strength of a stimulus that can be detected half the time. It can only be detected half the time because the minimum level of stimulation that can be detected varies from person to person and from trial to trial. Because of this human variability, researchers have arbitrarily set the limits as the minimum level of stimulation that can be detected half the time. EX: the absolute threshold for smell is one drop of perfume throughout a three-room apartment. For vision, a candle flame 30 miles away on a clear, dark night. For taste, one teaspoon of sugar in two gallons of water. For touch, a bee's wing falling onto your check from a height of ~ half an inch. For hearing a tick of a watch from 20 feet away.

perceptual set

the tendency to perceive objects or situations from a particular frame of reference. Perception can be influenced by an individual's expectations, motives, and interests. The term perceptual set refers to the tendency to perceive objects or situations from a particular frame of reference. Perceptual sets usually lead us to reasonably accurate conclusions. EX: Someone with an avid interest in Bigfoot might readily interpret an unusual figure in the woods as the beast. Sightings of UFOs , mermaids, and the Loch Ness monster that turn out to be unusual cloud formations,, manatees, or floating logs are all examples of perceptual set.

Tri-chromatic theory of color vision

there are three varieties of cones. Each type of cone is especially sensitive to certain wavelengths: red light (long wavelengths), green light (medium wavelengths), and blue light (short wavelengths). A given cone will be very sensitive to one of the three colors and only slightly responsive to the other two. When a color other than red, green, or blue strikes the retina, it stimulates a combination of cones. For example, if yellow light strikes the retina, both the red sensitive and green-sensitive cones are stimulated; purple light evokes strong reactions from red-sensitive and blue-sensitive cones. The trichromatic theory of color vision received research support in 1964 when George Wald showed that different cones were indeed activated by red, blue, and green light. EX: The trichromatic theory provides a good explanation for the most common form of color blindness: red-green color blindness. People with red-green color blindness cannot discriminate between red and green. That's because they have normal blue-sensitive cones, but their other cones are either red-sensitive or green-sensitive. Thus, red and green look the same to them.

vestibular sense and semicircular canals

vestibular sense: the technical name for the sense of balance or equilibrium. The two senses of vestibular sensory information, semicircular canals and vestibular sacs EX: When you experience environmental motion, like the rocking of a boat in choppy water, the fluids in the semicircular canals and the vestibular sacs are affected. Changes in your body's position, such as falling backward in a heroic attempt to return a volleyball serve also affect the fluids. Semicircular canals: located in the ear and are filled with fluid and lined with hair-like receptor cells that shift in response to the motion, changes in body position, or changes in gravity EX: when you experience turbulence on a plane, environmental motion, the fluids in the semicircular canals are affected