Chapter 6 Flashcards
What is sensation?
The reception and representation of environmental stimuli by the sensory receptors and nervous system.
What is perception?
The organization and interpretation of sensory information by the brain that enables us to make meaningful sense of it and use it to recognize objects or events.
What are sensory receptors?
Nerve endings that enable sensation.
What is bottom-up processing?
Information processing that begins with sensory receptors and works up to higher, integrative levels of processing. Allows your brain to detect the lines, colours, and angles that form images.
What is top-down processing?
Information processing that constructs perception from sensory input by drawing on experiences and expectations. Allows your brain to interpret what is detected by your senses.
What three steps are basic to all of our sensory systems?
Receiving sensory stimulation, transforming it into neural impulses, and delivering it to our brain in the form of neural information.
What is transduction?
The transformation of one form of energy (such as light) into another form our brain can use and interpret (such as images).
What is psychophysics?
The study of how we experience physical phenomena psychologically.
What is the distinction between sensation and perception?
Sensation is the bottom-up process of receiving sensory information, which is then represented by the nervous system. Perception is the top-down process of creating meaning from that sensory information through the brain’s interpretation of what is detected by sensation.
What is an absolute threshold?
The minimum intensity at which a person can detect a stimulus half the time. “The minimum stimulation needed to detect a particular stimulus (such as an approaching bike on the sidewalk behind you) 50 percent of the time.”
What is signal detection theory?
A theory that predicts how and when we will detect the presence of a weak stimulus (or signal) against background stimulation. Assumes that absolute thresholds vary, and that one’s ability to detect a signal depends on experience, expectations, motivations, and alertness.
What does one’s ability to detect a weak signal depend on according to signal detection theory?
Experience, expectations, motivations, and alertness.
What is subliminal?
Something that is below one’s absolute threshold.
How are we affected by subliminal stimuli?
“We do sense some stimuli subliminally—less than 50 percent of the time—and can be affected by these sensations. But although we can be primed, subliminal sensations have no powerful, enduring influence.”
What is the difference threshold?
The “just noticeable difference,” or the minimum difference between two stimuli required to distinguish between them half the time.
What causes the difference threshold to increase?
The size of the stimulus. It is easier to detect an addition of 5 decibels to 40 decibels than to 110 decibels.
What is Weber’s law?
“The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount).”
When does subliminal stimulation happen?
“When, without your awareness, your sensory system processes a signal that is below your absolute threshold.”
What is sensory adaptation?
“Diminished sensitivity as a consequence of constant stimulation.” Nerve cells firing with less frequency as the result of a constant, unchanging stimulus.
Why do objects not disappear from our sight because of sensory adaptation when we stare at them for a long time?
Because our eyes are constantly moving, ensuring our visual sensory receptors are constantly picking up on change.
What is the purpose of sensory adaptation?
Allowing us to focus on changes in our environment.
Why is it that after wearing shoes for a while, you cease to notice them?
Because of sensory adaptation.
What is a perceptual set?
A set of mental tendencies and assumptions that predisposes us to perceive one thing and not another.
What determines our perceptual set?
Our schemas, the organizing concepts we form through experience.
Besides perceptual set, what influences our interpretations of stimuli?
Context, emotion, and motivation.
Does perceptual set involve bottom-up or top-down processing? Why?
“Perceptual set involves top-down processing, because it draws on your experiences, assumptions, and expectations when interpreting stimuli.”
What is wavelength?
The distance between two wave peaks of a light wave.
What is hue?
The colour we experience on account of wavelength.
What is amplitude?
The height of a wave from peak to trough, determining the intensity of light and brightness of colours.
What is amplitude?
The height of a wave from peak to trough, determining the intensity of light and brightness of colours, or the volume of sound.
What is frequency?
“The number of complete wavelengths that pass a point in a given time (for example, per second).”
What is the cornea?
The outer part of the eye that bends light to increase focus.
What is the pupil?
An adjustable opening through which light passes.
What is the iris?
A muscle that dilates or constricts in response to light intensity, controlling the size of the pupil.
What is the 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.”
What is accommodation?
“The process by which the eye’s lens changes shape to focus near or far objects on the retina.”
What is the lens?
A structure behind the pupil that focuses light on the retina.
What causes myopia?
When the lens focuses light just before the retina.
What are the characteristics of the energy that we see as visible light?
“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 shorter blue-violet wavelengths to the longer red light wavelengths.”
What structures in the eye help focus light energy to create vision?
“After entering the eye through the cornea, passing through the pupil and iris, and being focused by a lens, light energy particles strike the eye’s inner surface, the retina.”
What does the hue of light depend on?
Wavelength.
What does the hue of light depend on?
Wavelength. Shorter waves produce colours closer to blue-violet and longer waves produce colours closer to red.
What are bipolar cells?
Cells in the retina that react to chemical changes in the rods and cones to activate ganglion cells.
What are ganglion cells?
Cells in the retina whose axons combine to form the optic nerve.
In what order does light pass through various stages from the retina to the visual cortex?
To the rods and cones, then the bipolar cells, then the ganglion cells, through the optic nerve, through the thalamus, before reaching the visual cortex.
What are cones?
“Retinal receptors that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. Cones detect fine detail and give rise to color sensations.”
What are cones?
“Retinal receptors that are concentrated near the center of the retina (around the fovea) and that function in daylight or in well-lit conditions. Cones detect fine detail and give rise to color sensations.” Cones also detect white.
What are rods?
“Retinal receptors that detect black, white, and gray, and are sensitive to movement. Rods are necessary for peripheral and twilight vision, when cones don’t respond.” Rods detect peripheral motion.
What is the blind spot?
The spot where the optic nerve leaves the eye, which has no receptor cells, experienced on the nose side of each retina. The brain fills in the blind spot so you don’t perceive it.
Which eye’s blind spot do objects on your left fall into?
The left eye.
Why doesn’t the blind spot impair vision?
Because your eyes are always moving and each eye catches what the other eye misses. Even with one eye closed, the brain fills in your blind spot so you don’t notice it.
What is the fovea?
The area of central focus on the retina, around which the cones are clustered.
Why are cones able to detect fine detail?
Because many cones have a direct connection to a single bipolar cell that relays their information to the visual cortex.
What are the differences between rods and cones?
There are more rods than cones. Cones cluster at the center of the retina while rods are located around the periphery. Cones only function in well-lit conditions and detect colour and detail. Rods can function in low light conditions and enable black and white vision. Rods don’t have a direct connection to a bipolar cell, but work in groups to send information to a bipolar cell.
How long does it take for your eyes to adjust to a change in light?
About 20 minutes or more.
What is the optic chiasm?
An X-shaped structure formed by the crossing of the optic nerves in the brain.
Half of each eye’s sensory information arrives in:
The opposite half of the brain.
How do the rods and cones process information?
“Light entering the eye triggers chemical changes that convert light energy into neural impulses. Photoreceptors called cones and rods at the back of the retina each provide a special sensitivity—cones to detail and color, rods to faint light and peripheral motion.”
What is the Young-Helmholtz trichromatic colour 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.”
What is an afterimage?
The phenomenon that occurs when you stare at a colour image for a long time before looking at a blank white space, and seeing the image colour-inverted.
What is opponent-process theory?
“The theory that opposing retinal processes (red-green, blue-yellow, 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.” Basically, red and green messages cannot be processed at the same time, but one inhibits the other.
How do we perceive color in the world around us?
Colour processing happens in two stages. First, cones sensitive to red, green, and blue respond to different colour stimuli. Then neurons in the retina and thalamus code the information from the cones into pairs of opponent colours.
What are feature detectors?
“Nerve cells in the brain’s visual cortex that respond to specific features of the stimulus, such as shape, angle, or movement.”
Who discovered feature detectors?
David Hubel and Torsten Wiesel.
Who discovered trichromatic colour theory?
Hermann von Helmholtz and Thomas Young.
Who discovered opponent-process theory?
Ewald Hering.
What is a supercell cluster?
A team of nerve cells that responds to complex patterns.
What is the fusiform face area?
A brain region located in the temporal lobes that allows us to identify faces. It is especially active in the right temporal lobe.
Where are feature detectors located?
In the occipital lobe’s visual cortex.
What do feature detectors do?
“Respond to specific features of the visual stimulus, such as shape, angle, or movement. Feature detectors pass information on to other cortical areas, where supercell clusters respond to more complex patterns.”
What is parallel processing?
“Processing many aspects of a stimulus or problem simultaneously.”
How does the brain use parallel processing to analyze a visual scene?
By analyzing the subdimensions of the visual scene (motion, form, depth, colour) simultaneously.
In what order does visual information processing occur?
Stimulus, retinal processing, feature detection, parallel processing, recognition.
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 eyes. Receptor cells in your retina convert the light waves’ energy into neural impulses sent to your brain. Your brain detector cells and work teams process the subdimensions of this visual input—including color, movement, form, and depth—separately but simultaneously. Your brain interprets this information, based on previously stored information and your expectations, and forms a conscious perception of your friend.”
What is gestalt?
“An organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.”
What is figure-ground?
“The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).”
What is grouping?
“The perceptual tendency to organize stimuli into coherent groups.”
What is the proximity principle of grouping?
The tendency to perceive figures close together as being part of a group.
What is the continuity principle of grouping?
The tendency to perceive continuous patterns rather than discontinuous or alternating ones.
What is the closure principle of grouping?
The tendency to fill in gaps to create a complete, whole object.
What are three principles of grouping?
Closure, continuity, proximity.
How do figure-ground and grouping principles influence our perceptions?
“To recognize an object, we must first perceive it (see it as a figure) as distinct from its surroundings (the ground). We bring order and form to stimuli by organizing them into meaningful groups, following such rules as proximity, continuity, and closure.”
What is depth perception?
The ability to see in three dimensions, despite the images that reach our retinas being two-dimensional, which allows us to judge distances.
What is a visual cliff?
A model of a cliff used in laboratory settings to test depth perception in babies and young animals.
