What is the difference between sensation and perception?
Sensation is what happens when our sensory modalities (vision, hearing, taste, etc.) are activated.
Perception is how we understand these senses.
What are the three stages of sensation?
transmission through neural pathways to the brain
Stimuli from the outside world are converted into neural impulses to be processed by our brains through what process?
What two processes stop you from feeling your shirt press against the hairs on your arms all day?
sensory adaptation: when the hairs on our arms are constantly being pressed, we simply stop responding to the feeling of pressure
sensory habituation: the pressure on our hairs stops being novel, so there is no reason for us to continue paying attention to it
If you are zoning out in class and your teacher suddenly uses a swear word, you will snap back to attention. What is the phenomenon called that is responsible for this?
The cocktail party phenomenon/effect involuntarily focuses our attention on something salient, like hearing our name in a roomful of people, or hearing a teacher curse.
What are the "energy senses" and why are they called that?
These senses convert stimuli into energy, like light, sound waves, and pressure.
What are the "chemical senses" and why are they called that?
These senses take stimuli and convert them into chemical signals to be processed.
What is a human's dominant sense?
What are the factors in seeing a bright light or a blue sky versus a black jacket?
Light intensity will affect how bright an object appears, and color or hue is affected by the light wavelength in the visual color spectrum an object reflects. Objects that appear black actually absorb all colors, while objects that are white reflect all light wavelengths. The blue sky absorbs all colors but blue, which it reflects.
The cornea is the protective covering of the eye, where light first enters and is focused.
The black part in the middle of the eye, the pupil acts like the shutter of a camera, and is controlled by the iris.
The iris is the colored disc surrounding the pupil that changes its dilation, allowing more or less light in.
The lens focuses light entering through the pupil (called accomodation), then flips and inverts the image and projects it onto the retina.
The upside-down and inverted image is projected onto the retina, where neurons are activated to interpret the image via transduction. The retina has several layers of cells involved in transduction.
What are the parts of the retina?
- rods and cones
- ganglion cells
- blind spot
When the sun sets and everything in the dark around you looks bluish, are your rods or your cones activated?
Rods are activated. Rods react to light, rather than color, with the exception of blue, which explains why we can only see shades of blue in the dark. Cones are activated by other colors.
The fovea is an indentation in the retina. It is the eye's fixation point, or the part of the eye used when attending to detail.
Why do we have a "blind spot"?
The area where the optic nerve leaves the retina has no photoreceptors (rods or cones).
The optic nerve is comprised of axons from what?
What is the lateral geniculate nucleus (LGN)?
It is the visual part of the thalamus that receives information from the optic nerve.
Information from the left side of the retinas go to the left side of the brain, and information from the right side of the retinas go to the right side of the brain. Where does the information get routed to each side?
Since the optic chiasm, where this information intersects, is shaped like an X, an easy way to remember this is to remember that "chi" is the letter X in Greek.
After visual impulses are processed in the thalamus, where do they end up?
Vision is ultimately processed by the occipital lobe.
There are five feature detectors in vision, labeled V1 through V5. Who won the Nobel Prize for their discovery?
David Hubel and Torsten Wiesel
In the context of vision, what does each of the five feature detectors do?
V1. mental image formation and imagination
V2. illusory contours
V4. color analysis and pattern recognition
V5. motion and direction
What is the trichromatic theory?
It is the theory that the cones in our retinas perceive blue, green, and red, and are activated in combination to create a perception of all the colors in the visual spectrum.
When you look at the sun for a while and then look away, why is there a dark spot in your vision for a period of time?
This is called an afterimage. Afterimages of red are green, and afterimages of blue are yellow and vice-versa. The opponent-process theory states that when you look at something of one color, you inhibit its color pair, which you see when you look away.
Why would the opponent-process theory help explain color blindness?
The opponent process theory hypothesizes that the retina has its sensory receptors arranged in color pairs, and if a person is missing a specific pair, he will be unable to perceive either of those colors.
What characteristics of a sound wave determine what we actually hear?
The amplitude of a soundwave determines the loudness of a sound (decibels).
The frequency of a soundwave determines the pitch of a sound (hertz).
The pinna is the flap of skin outside the ear that helps capture and focus sound.
The eardrum or tympanic membrane concentrates sound energy, vibrating when sound from the ear canal hits it.
Ossicles are three tiny bones in the middle ear that connect the eardrum to the oval window.
- hammer (malleus)
- anvil (incus)
- stirrup (stapes)
The oval window compresses the fluid in the cochlea and connects the middle ear to the inner ear.
The fluid-filled cochlea is small and coiled, like a snail's shell, and converts vibrational activity into neural energy.
organ of Corti
The organ of Corti is the part within the cochlea that actually converts soundwaves into neural energy. The hair cells attached to the basilar membrane on the cochlea move in response to compression of fluid, which causes transduction in the organ of Corti, sending neural information to the brain.
What is place theory?
Place theory believes that pitch processing is activated spatially on receptors in the cochlea, the same way that a piano's notes are arranged spatially. A higher pitch would move a hair cell on a certain part of the cochlea that a lower pitch would not.
What is frequency theory?
Frequency theory (or volley theory) says that we hear different pitches because of the frequency at which the hair cells in the cochlea fire.
When you go to a loud concert and stand by the speakers, what kind of deafness are you causing for yourself?
Loud noises damage the hair cells on the cochlea, preventing them from firing for any sounds at all, so no neural impulses reach the brain.
What kind of deafness is caused when one of the mechanisms used to move sound from the outer ear to the cochlea is damaged?
What sensory modality responds to pressure or temperature?
If you stub your toe, then fall down and break your wrist, which one will you feel more, and what theory predicts this?
You will feel your broken wrist more than your stubbed toe, which is predicted by gate-control theory.
This theory hypothesizes that pain messages are prioritized and the high-priority messages will be delivered first, while the low-priority messages will be shut out, like a swinging gate.
Pain killers also help close the gate, as will natural endorphins in the brain.
What are papillae?
Papillae are the bumps on your tongue that hold taste buds.
What are the five different tastes we perceive?
umami (savory or meaty tastes)
What is another word for "taste"?
What makes smell different from the other senses? Why do certain smells trigger memories?
It is not processed through the thalamus. Instead, the nerves of the olfactory bulb connect with the amygdala and hippocampus, which are attached to memory and emotional response.
What sense is responsible for motion sickness on a roller coaster?
The vestibular sense responds to your body's orientation in space. There are canals in your ear that are filled with fluid, and the position of that fluid tells your brain where you are. If you are on a bumpy, looping roller coaster, your vestibular sense may be confused, causing nausea and dizziness.
What is the kinesthetic sense in charge of?
The kinesthetic sense keeps track of specific body parts and where they are in space, using receptors in joints and muscles.
What is the absolute threshold?
It is the smallest stimulus consciously perceptible at least 50% of the times encountered. Stimuli below the absolute threshold are considered subliminal.
If your parents ask you to turn down the television, what determines how much you have to turn it down before they notice a change in volume?
The difference threshold (or just-noticeable difference) is the amount a stimulus needs to change before the change can be detected. For hearing, the change must be 5%.
What is the Weber-Fechner law?
It asserts that the amount of stimulus change needed to perceive a difference is proportional to the intensity of the existing stimulus.
- If there is one candle in a room and another candle is added, you will notice a difference in brightness. However, if there are 17 candles on a birthday cake, an 18th will likely not be noticeable
What theory takes into account the things that distract us from perceiving a stimulus?
Signal detection theory acknowledges the motivation to perceive a certain stimulus, like smelling delicious food when we're hungry, or not noticing a friend in a crowded room.
What is top-down processing?
Top-down processing uses information we already have in our brains to fill in gaps in the things we sense. It can frequently overrule the more primitive areas of our brains.
Building a perception of an object by mentally compiling all of its features is called what?
bottom-up processing or feature analysis
This is slower than top-down processing, but is more thorough and less prone to mistakes.
What are the four Gestalt rules of perception?
Items close together are easy to perceive as being part of the same group.
Items that form a continuous pattern are easier for the mind to see as part of the same group.
Items that look alike are more likely to be seen as being in the same group.
Items that form a known image are easier to group together, even if there are some gaps within the image.
While objects frequently remain the same, the way we view them does not. What allows us to still recognize an item despite the changes in how we see it?
Constancy allows this to happen. There are three types of constancy:
- size constancy
- shape constancy
- brightness (or color) constancy
What prevents us from thinking an object is actually changing in size as we walk toward it?
Size constancy helps take distance into account when calculating the size of an object.
What allows us to see different properties of an object from different angles but know it is still the same object?
Though an understanding of the object has to exist to begin with, the principle of shape constancy allows our brains to recognize that, even if we see a piano from behind instead of looking at its keys, it is still a piano.
__________ allows us to know that the color of an object does not change, even though the light hitting it does change.
Brightness constancy (or color constancy)
Eleanor Gibson terrified babies by pioneering what experiment? What does this experiment measure?
Gibson pioneered the visual cliff experiment, which measures depth perception in babies.
A baby is placed on one end of a table and tries to cross to the other side. However, the middle of the table appears hollow, like a cliff, and babies who refuse to cross the cliff can perceive depth.
__________ are used to perceive depth, and require use of both eyes, while __________ only require use of one eye.
Binocular cues; monocular cues
What are examples of monocular cues?
- linear perspective
- relative size cues
- interposition cues
- texture gradient
Like in art class, linear perspective uses a point on the canvas for two lines to come together, representing distance.
relative size cues
To represent distance, objects in photos or drawings tend to be larger the closer they are to the foreground. If something is in the distance, it is usually represented as being quite small.
Interposition cues signal to a viewer that an object obscuring the view of another object is closer to the viewer.
Things in the distance are difficult to see clearly, and things close-up are more detailed, so fuzzy textures signal that an object or landscape is in the distance.
Shadowing uses light and darkness to signal to the viewer the location of objects.
What are two binocular cues to help us perceive depth?
binocular disparity (or retinal disparity)
Why does binocular disparity tell us how far away an object is?
Our eyes are positioned apart from one another, so when one eye perceives something different about an object from the other eye, it tells us that the object must be close. If the object were far away, both eyes would perceive roughly the same thing.
How does convergence signal how far away an object is?
The muscles that control the eyes send signals to the brain as they move, and the more the eye muscles converge (turn inward together), the closer an object must be.
What muscles control the shape of the lens?
Rods and cones are also known as what?
In what part of the retina is visual acuity at its greatest?
The fovea, since it has the greatest concentration of cones in the eye, enabling perception of fine detail.
How would nativists explain perception?
Nativists would argue that perception is innate.
How would structuralists explain perception?
Structuralists would argue that perception is a result of bottom-up processing stemming from sensory input.
How would gestalt psychologists explain perception?
They would argue that perception is a result of top-down processing, since the way people explain the world is by creating a system of organization.
What type of illusion is this?
an ambiguous figure illusion
They are images that can be perceived differently depending on how they are seen.
What kind of illusion is this?
a figure-ground reversal pattern illusion
These images can be perceived differently based on which part is seen as the foreground and which is the background (in this case, faces or a vase).
What kind of illusion is this?
an impossible object illusion
Impossible objects are perceived as being real, even though there is no geometric way they can exist in reality.
Why does the moon look smaller in the sky than it does on the horizon?
When the moon is on the horizon, we can compare its relative size to other familiar objects. However, when it is in the sky, we have nothing else to compare it to, creating the illusion that it is smaller.
How are cartoons an example of the phi phenomenon?
Cartoons are a series of still images changed slightly and presented quickly to achieve a sense of fluid motion. The phi phenomenon states that we attribute apparent motion to a series of still images that differ slightly from one another.
What is this illusion?
the Müller-Lyer illusion
Though we know the lines are equal in length, we perceive the one with outward prongs as longer than the one with inward prongs.
What type of illusion is this?
a Ponzo illusion
Like the Muller-Lyer illusion, the lines in this example seem different in length, though they are the same.
What are people with prosopagnosia unable to do?
Prosopagnosia appears to affect the fusiform gyrus and can be either following brain trauma or congenital.
Why does a single light in darkness appear to move?
The constant motion of our own eyes causes static objects to appear in motion, which is referred to as the autokinetic effect.
Why is it that dogs can respond to higher-pitched sounds than humans?
Dogs have a different terminal threshold than humans. The terminal threshold is the upper limit of perceivable stimuli, so while humans are unable to recognize high-pitched tones, dogs can still distinguish them.
What does the basilar membrane do?
The basilar membrane vibrates in response to sound coming from the stapes.
What type of cells respond to pain and temperature changes in the skin?
free nerve endings
What do Pacinian corpuscles respond to?
What are the fast-adapting skin receptor cells that respond to light touch?
What is the two-point threshold?
It is the point at which touch from two separate objects is recognized. Different places on the body have smaller or larger two-point thresholds.
When you feel neither warm nor cold, your skin may be experiencing what?
Usually around 85 degrees farenheit, this is the point at which your skin will not feel temperature sensations.
Mirror boxes have been shown to reduce what?
phantom limb pain
Phantom limb pain is when an amputee feels pain in the limb that is no longer attached.
What causes us to turn in the direction of something touching us?
the orienting reflex
Who defined the just-noticeable difference (or differential threshold)?
E. H. Weber
What is the visual field?
The visual field is the total perceptible area at any given time without moving your head or eyes.
What causes us to understand that a train is in the distance because it appears to be moving slowly and a train is close because it appears to be moving quickly?
the motion parallax
What causes perceived differences in brightness in visual regions?
Interconnected neurons inhibit each other to produce contrast at the edges of regions.
Who suggested the tri-color theory (or component theory)?
Thomas Young and Hermann von Helmholtz
Helmholtz is also known for his theory on color blindness.
What neuronal layers stand between the rods and cones and the optic nerve?
What are the three types of cells Hubel and Wiesel differentiated with regard to signal detection theory?
simple: concerned with boundaries and orientation of an object
complex: information about movement
hypercomplex: information about shape
What photopigment is contained in the rods?
The law of prägnanz allows us to find complex and specific details in objects.
The law of prägnanz says we organize the things we perceive in the simplest or most orderly way possible.
What type of motion occurs when a stationary point of light has the appearance of movement against a moving background?
The motion aftereffect states that if we see an object in motion for a long time and then it stops, it will appear to move in the ______ direction even though it is not moving at all.
What did Fantz's experiments demonstrate about preferential looking in babies?
If they looked at different stimuli for different periods of time, that meant they could tell a difference between the objects
if they spent more time looking at one object than another, it signaled preference
babies prefer to look at complex objects, like faces and patterns more than uniform objects.
What brain structures are important for visual processing?
lateral genigulate nucleus (thalamus)
visual cortex (occipital lobe)
What brain structures are important for auditory processing?
medial geniculate nucleus (thalamus)
auditory cortex (temporal lobe)
What brain structure is important for processing touch?