Psychology Chapter 6 (2)
Examples of grouping
*Proximity-We group nearby figures together. We see not six separate lines, but three sets of two lines. *Continuity-We perceive smooth, continuous patterns rather than discontinuous ones. This pattern could be a series of alternating semicircles, but we perceive it as two continuous lines—one wavy, one straight. *Closure-We fill in gaps to create a complete, whole object. Thus we assume that the circles on the left are complete but partially blocked by the (illusory) triangle. Add nothing more than little line segments to close off the circles and your brain stops constructing a triangle.
Visual Information Processing
*scene *retinal processing- Receptor rods &Cones-->Bipolar cells-->ganglion cells *feature detection- Brains detector cells respond to specific features- edges, lines, angles *parallel processing- Brain cell teams process combined info on color, movement, form and depth. *recognition- brain interprets the constructed image based on stored images.
How do we perceive color in the world around us?
According to the Young-Helmholtz trichromatic (three-color) theor y, the retina contains three types of color receptors. Contemporary research has found three types of cones, each most sensitive to the wavelengths of one of the three primary colors of light (red, green, or blue). Hering's opponent-process theory proposed three additional color processes (red-versus-green, blue-versus-yellow, black-versus-white). Research has confirmed that, en route to the brain, neurons in the retina and the thalamus code the color-related information from the cones into pairs of opponent colors. These two theories, and the research supporting them, show that color processing occurs in two stages.
Cats are able to open their :
Cats are able to open their pupils much wider than we can, which allows more light into their eyes so they can see better at night.
cones and rods
Cones also enable you to perceive color. In dim light they become ineffectual, so you see no colors. Rods, which enable black-and-white vision, remain sensitive in dim light. Several rods will funnel their faint energy output onto a single bipolar cell. Thus, cones and rods each provide a special sensitivity—cones to detail and color, and rods to faint light and peripheral motion.
What does research on restored vision, sensory restriction, and perceptual adaptation reveal about the effects of experience on perception?
Experience guides our perceptual interpretations. People blind from birth who gained sight after surgery lack the experience to visually recognize shapes, forms, and complete faces. Sensory restriction research indicates that there is a critical period for some aspects of sensory and perceptual development. Without early stimulation, the brain's neural organization does not develop normally. People given glasses that shift the world slightly to the left or right, or even upside down, experience perceptual adaptation. They are initially disoriented, but they manage to adapt to their new context.
supercell clusters
Feature detectors pass this specific information to other cortical areas, where teams of cells (supercell clusters) respond to more complex patterns.
What do we mean when we say that, in perception, the whole may exceed the sum of its parts?
Gestalt psychologists used this saying to describe our perceptual tendency to organize clusters of sensations into meaningful forms or coherent groups.
How do the rods and cones process information, and what is the path information travels from the eye to the brain?
Light entering the eye triggers chemical changes in the light-sensitive rods and color-sensitive cones at the back of the retina, which convert light energy into neural impulses. After processing by bipolar and ganglion cells, neural impulses travel from the retina through the optic nerve to the thalamus, and on to the visual cortex.
What is the rapid sequence of events that occurs when you see and recognize a friend?
Light waves reflect off the person and travel into your eye, where the receptor cells in your retina convert the light waves' energy into neural impulses sent to your brain. Your brain processes the subdimensions of this visual input—including depth, movement, form, and color—separately but simultaneously. It interprets this information based on previously stored information and your expectations, and forms a conscious perception of your friend
ow do perceptual constancies help us construct meaningful perceptions?
Perceptual constancies enable us to perceive objects as stable despite the changing image they cast on our retinas. Color constancy is our ability to perceive consistent color in objects, even though the lighting and wavelengths shift. Brightness (or lightness) constancy is our ability to perceive an object as having a constant lightness even when its illumination—the light cast upon it—changes. Our brain constructs our experience of an object's color or brightness through comparisons with other surrounding objects. Shape constancy is our ability to perceive familiar objects (such as an opening door) as unchanging in shape. Size constancy is perceiving objects as unchanging in size despite their changing retinal images. Knowing an object's size gives us clues to its distance; knowing its distance gives clues about its size, but we sometimes misread monocular distance cues and reach the wrong conclusions, as in the Moon illusion.
Nocturnal Animals
Some nocturnal animals, such as toads, mice, rats, and bats, have impressive night vision thanks to having many more rods than cones in their retinas. These creatures probably have very poor color vision.
What are two key theories of color vision? Are they contradictory or complementary? Explain.
The Young-Helmholtz trichromatic theory shows that the retina contains color receptors for red, green, and blue. The opponent-process theory shows that we have opponent-process cells in the retina and thalamus for red-green, yellow-blue, and white-black. These theories are complementary and outline the two stages of color vision: (1) The retina's receptors for red, green, and blue respond to different color stimuli. (2) The receptors' signals are then processed by the opponent-process cells on their way to the visual cortex in the brain.
Transduce
To convert from one form of energy to another (e.g., from light to neural electrical energy, or from mechanical movement to neural electrical energy).
How do we normally perceive depth?
We are normally able to perceive depth thanks to the binocular cues that are based on our retinal disparity, and monocular cues including relative height, relative size, interposition, linear perspective, light and shadow, and relative motion.
What are the characteristics of the energy that we see as visible light? What structures in the eye help focus that energy?
What we see as light is only a thin slice of the broad spectrum of electromagnetic energy. The portion visible to humans extends from the blue-violet to the red light wavelengths. After entering the eye and being focused by a lens, light energy particles strike the eye's inner surface, the retina. The hue we perceive in a light depends on its wavelength, and its brightness depends on its intensity.
Blind Spot
Your blind spot is on the nose side of each retina, which means that objects to your right may fall onto the right eye's blind spot. Objects to your left may fall on the left eye's blind spot. The blind spot does not normally impair your vision, because your eyes are moving and because one eye catches what the other misses. the point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there.
retinal disparity
a binocular cue for perceiving depth by comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object. (Closing your eyes, one eye, another eye trick)
visual cliff
a laboratory device for testing depth perception in infants and young animals
Iris
a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening
gestalt
an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.
Cones are the eye's receptor cells that are especially sensitive to __________ light and are responsible for our __________ vision.
bright;color
The amplitude of a light wave determines our perception of
brightness
monocular cues
depth cues, such as interposition and linear perspective, available to either eye alone
binocular cues
depth cues, such as retinal disparity, that depend on the use of two eyes
The cells in the visual cortex that respond to certain lines, edges, and angles are called ____________ ____________.
feature detectors
In listening to a concert, you attend to the solo instrument and perceive the orchestra as accompaniment. This illustrates the organizing principle of
figure-ground
In terms of perception, a band's lead singer would be considered___________________ (figure/ground), and the other musicians would be considered___________________ (figure/ground).
figure;ground
Ewald Hering and the Hering Opponent process theory
found a clue in afterimages. Stare at a green square for a while and then look at a white sheet of paper, and you will see red, green's opponent color. Stare at a yellow square and its opponent color, blue, will appear on the white paper. Hering formed another hypothesis: There must be two additional color processes, one responsible for red-versus-green perception, and one for blue-versus-yellow.
Our tendencies to fill in the gaps and to perceive a pattern as continuous are two different examples of the organizing principle called
grouping
perpetual adaptation
in vision, the ability to adjust to an artificially displaced or even inverted visual field
Two examples of ___________ depth cues are interposition and linear perspective.
monocular
feature detectors
nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement
feature detectors
nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement.
The brain's ability to process many aspects of an object or a problem simultaneously is called ____________ ____________.
parallel processing
color consistency
perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object. This would be clear if you viewed an isolated tomato through a paper tube over the course of a day. The tomato's color would seem to change as the light—and thus the wavelengths reflected from its surface—changed. But if you viewed that tomato as one item in a salad bowl, its color would remain roughly constant as the lighting shifted.
perpetual constancy
perceiving objects as unchanging even as illumination and retinal images change. a top-down process. Regardless of the viewing angle, distance, and illumination, we can identify people and things in less time than it takes to draw a breath, a feat that challenges even advanced computers and has intrigued researchers for decades. This would be a monumental challenge for a video-computer system.
In experiments, people have worn glasses that turned their visual fields upside down. After a period of adjustment, they learned to function quite well. This ability is called __________ __________.
perceptual adaption
After surgery to restore vision, patients who had been blind from birth had difficulty
recognizing objects by sight
Cones
retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations. Also enable you to see color. In dim light they become ineffectual, so you see no colors.
Rods
retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond
depth perception
the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance
Pupil
the adjustable opening in the center of the eye through which light enters
intensity
the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude(height)
Fovea
the central focal point in the retina, around which the eye's cones cluster
Hue
the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth
Wavelength
the distance from the peak of one light wave or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission.
Retina
the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information. Behind the pupil is a transparent lens that focuses incoming light rays into an image on the retina, a multilayered tissue on the eyeball's sensitive inner surface.
optic nerve
the nerve that carries neural impulses from the eye to the brain. The optic nerve is an information highway to your brain, where your thalamus stands ready to distribute the information it receives. This nerve can send nearly 1 million messages at once through its nearly 1 million ganglion fibers. (The auditory nerve, which enables hearing, carries much less information through its mere 30,000 fibers.)
The blind spot in your retina is located where
the optic nerve leaves the eye
figure-ground
the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).
grouping
the perceptual tendency to organize stimuli into coherent groups.Our minds bring order and form to stimuli by following certain rules for grouping, also identified by the Gestalt psychologists. These rules, which we apply even as infants and even in our touch perceptions, illustrate how the perceived whole differs from the sum of its parts
accommodation
the process by which the eye's lens changes shape to focus near or far objects on the retina. The lens focuses the rays by changing its curvature and thickness.
parallel processing
the processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision
Hering Opponent Process Theory
the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.
Young-Helmholtz trichromatic (three-color) theory
the theory that the retina contains three different types of color receptors—one most sensitive to red, one to green, one to blue—which, when stimulated in combination, can produce the perception of any color.
Two theories together account for color vision. The Young-Helmholtz trichromatic theory shows that the eye contains ____________, and the opponent-process theory accounts for the nervous system's having ____________.
three types of color receptors; opponent-process cells
The characteristic of light that determines the color we experience, such as blue or green, is:
wavelength
David Hubel and Torsten Wiesel
who showed that our brain's computing system deconstructs visual images and then reassembles them. Hubel and Wiesel received a Nobel Prize for their work on feature detectors, nerve cells in the brain that respond to a scene's specific visual features—to particular edges, lines, angles, and movements.
