Chapter 6: Sensation and Perception Flashcards
What is prosopagnosia?
Face blindness
What is sensation?
The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment
What are sensory receptors?
Sensory nerve endings that respond to stimuli
What is perception?
The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events
What is bottom-up processing?
Analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information
What is top-down processing?
Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations
What three steps are basic to all our sensory systems?
1) Receiving sensory stimulation
2) Transforming the stimulation into neural impulses
3) Delivering the neural information to our brain
What is transduction?
Conversion of one form of energy into another
What is transduction (in sensation)?
Transforming of stimulus energies, such as sight, sounds, and smells, into neural impulses our brain can interpret
What is the rough distinction between sensation and perception?
Sensation is a bottom-up process by which your sensory receptors receive and represent stimuli. Perception is a top-down process by which your brain creates meaning by interpreting what your senses detect.
What is absolute threshold?
The minimum stimulus energy needed to detect a particular stimulus 50 percent of the time
Who came up with the idea of absolute threshold?
German scientist and philosopher Gustav Fechner
To test one’s absolute threshold for sound, a hearing specialist would do what?
Send tones, at varying levels, into each of your ears and record whether you could hear each tone. The test results would show the point where, for any sound frequency, half the time you could detect the sound and half the time you could not. That 50-50 point would define your absolute threshold.
What are subliminal stimuli?
Stimuli that people cannot consciously detect 50 percent of the time (below people’s absolute threshold)
What is signal detection theory?
A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). It assumes that there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and alertness.
What is priming?
Priming is the idea that exposure to one stimulus may influence a response to a subsequent stimulus, without conscious guidance or intention.
What is the difference threshold (or the just noticeable difference [jnd])?
The minimum difference between two stimuli required for detection 50 percent of the time
What is the difference threshold also called?
Just noticeable difference (jnd)
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)
Using sound as your example, explain how these concepts differ: absolute threshold, subliminal stimulation, and difference threshold.
Absolute threshold: Minimum stimuli needed to detect it 50 percent of the time (such as bike sound behind you on the sidewalk)
Subliminal stimulation: When your sensory systems process stimuli that are below your absolute threshold i.e. you aren’t aware of them (such as a very far biker)
Difference threshold: Minimum difference in stimuli required for you to notice a change 50 percent of the time (such as a biker vs. a runner behind you on the sidewalk)
What is sensory adaptation?
Diminished sensitivity as a consequence of contact stimulation
Noticing a bad smell in your room which vanishes after a time that you have spend in the room (but which another person entering the room will notice) is an example of what?
Sensory adaptation
Why doesn’t an object vanish from sight when we continuously stare at it (which it should according to sensory adaptation)?
Because our eyes are continuously moving without our awareness, thus making sure that the stimulation on the eye receptors continually changes
Why is it that after wearing shoes for a while, you cease to notice them (until questions like this draw your attention back to them)?
The shoes provide constant stimulation. Thanks to sensory adaptation, we tend to focus primarily on changing stimuli.
What is a perceptual set?
A mental predisposition to perceive one thing and not another
What determines our perceptual set?
Through experience we form concepts, or schemas, that organize and interpret unfamiliar information (our preexisting schemas for monsters and tree trunks influence how we apply top-down processing to interpret ambiguous sensations such as the image of the Loch Ness monster).
Does perceptual set involve bottom-up or top-down processing? Why?
Top-down, because it draws on your experiences, assumptions, and expectations when interpreting stimuli
What three other aspects besides perceptual set influence our top-down processing?
Context, motivation, and emotion
How are we affected by subliminal stimuli?
We do sense some stimuli subliminally (less than 50 percent) and can be affected by these sensations. But although we can be primed, subliminal sensations have no powerful, enduring influence.
What is the point of sensory adaptation?
It focuses our attention on informative changes in our environment
Sensation is to ________________ as perception is to _____________.
a. absolute threshold; difference threshold
b. bottom-up processing; top-down processing
c. interpretation; detection
d. grouping; priming
b
The process by which we organize and interpret sensory information is called ______________.
Perception
Subliminal stimuli are
a. too weak to be processed by the brain.
b. consciously perceived more than 50 percent of the time.
c. strong enough to affect our behavior at least 75 percent of the time.
d. below our absolute threshold for conscious awareness.
d
Another term for difference threshold is the _____________________.
just noticeable difference
Weber’s law states that for a difference to be perceived, two stimuli must differ by
a. a fixed or constant energy amount.
b. a constant minimum percentage.
c. a constantly changing amount.
d. more than 7 percent.
b
Sensory adaptation helps us focus on
a. visual stimuli.
b. auditory stimuli.
c. constant features of the environment.
d. important changes in the environment.
d
Our perceptual set influences what we perceive.This mental tendency reflects our
a. experiences, assumptions, and expectations.
b. sensory adaptation.
c. priming ability.
d. difference thresholds.
a
What’s the difference between a bee’s visible light spectrum and a human’s?
Bees cannot see what we perceive as red but they can see ultraviolet light
What are the wavelengths of light that are visible to humans (in nm)?
Around 350nm - 750nm
We perceive the shortest waves in our visible spectrum as what color?
Blue-violet
We perceive the longest waves in our visible spectrum as what color?
Red
What is wavelength?
The distance from the peak of one light wave or sound wave to the peak of the next
Electromagnetic wavelengths vary from what type of waves to what type of wave?
From short gamma waves to long radio waves
What is hue?
The dimension of color that is determined by wavelength of light (what we know as the color names blue, green, and so on)
What is intensity of a light wave or sound wave?
The amount of energy in a light wave or sound wave
Intensity of a wave is determined by what?
A wave’s amplitude (height)
What is a wave’s amplitude?
It is it’s height distance from the peak to the bottom of the wave
What does the intensity of a light or sound wave influence?
It influences what we perceive as brightness or loudness
What is the frequency of a wave?
It is the amount of wave cycles that are occurring in a given time period
The shorter the wavelength the __________ the frequency.
higher
The longer the wavelength the ___________ the frequency.
lower
Light enters the eye through what?
The cornea
What part of the eye bends light to help provide focus?
The cornea
What does the cornea of the eye do?
It bends the light to help provide focus
What is the pupil?
A small adjustable opening of the eye
What is surrounding the pupil and controlling its size?
The iris
What is the iris?
A colored muscle that dilates or constricts the size of the pupil in response to light intensity
The iris constricts when it is a sunny day but when does it also constrict?
When you feel disgust or when you are about to answer “no” to a question
The iris dilates in a dark room but when does it also dilate?
When you have sexual desires or are interested
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 of the eye?
The process by which the eye’s lens changes shape to focus near or far objects on the retina
What is myopia?
Nearsightedness
What are rods?
Retinal receptors that detect black, white, and gray, and are sensitive to movement
What are rods necessary for?
Peripheral and twilight vision, when cones don’t respond
What are cones?
Retinal receptors that function in daylight or in well-lit conditions
Where on the retina are cones concentrated?
Near the center of the retina (around the fovea)
What do cones do?
They detect fine detail and give rise to color sensations
What is an optic nerve?
The nerve that carries neural impulses from the eye to the brain
What is the blind spot?
The point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there
What is the fovea?
The central focal point in the retina, around which the eye’s cones cluster
Where are rods located in the retina?
In the periphery of it
How many cones do we have?
6 million
How many rods do we have?
120 million
How is cone’s sensitivity in dim light?
Low
How is rod’s sensitivity in dim light?
High
How is cone’s color sensitivity?
High
How is rod’s color sensitivity?
Low
How is cone’s detail sensitivity?
High
How is rod’s detail sensitivity?
Low
How long does it take for the eyes to fully adapt to darkness?
Around 20 minutes
What is so special and interesting about the 20 minutes that it takes for the eyes to fully adapt to darkness?
That is usually the time it takes for the twilight transition between the Sun’s setting and darkness
Where is the visual cortex located?
In the occipital lobe at the back of your brain
Some nocturnal
animals, such as toads,
mice, rats, and bats,
have impressive night
vision thanks to having many more ________________ than ______________ in their retinas. These creatures probably have very poor _______________ vision.
rods; cones; color
Cats are able to open their _____________ much wider than we can, which allows more light into their eyes so they can see better at night.
pupils
What is the scientifically correct answer to “If a tree falls in the forest and no one hears it, does it make a sound” ?
No, because the tree only creates air pressure waves. They are only perceived as sound by a human standing close enough to hear it.
What is the 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 color
What is tetrachromatic color vision?
It is a genetic condition where humans (mostly female) are able to see up to 100 million colors
Humans can generally see differences among how many color variations?
More than 1 million
What is colorblindness?
The inability to distinguish between green and red (due to a lack of green-sensitive cones, red-sensitive cones, or both).
Who discovered the afterimage effect?
Ewald Hering
What color vision hypothesis did Ewald Hering form?
That color vision must involve two additional color processes, one responsible for red-versus-green perception, and one for blue-versus-yellow perception
What is the opponent-process theory?
The theory that opposing retinal processes (red-green, blue-yellow, white-black) enable color vision.
Color processing occurs in two stages. What are the two stages?
- The retina’s red, green, and blue cones respond in varying degrees to different color stimuli, as the Young-Helmholtz trichromatic theory suggested.
- The cones’ responses are then processed by opponent-process cells, as Hering’s theory proposed.
What are the two key theories of color vision?
Young-Helmholtz trichromatic theory and the opponent-process theory
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