textbook chapter 3 Flashcards
what can L.M do because of akinetopsia
detect that an object now is in a position different from its position moments ago
what can you infer motion from
the change in position you can not perceive the motion
what is the specificity of akinetopsia
a disruption of movement perception, with other aspects of perception still intact
what problems can you have if you have akinetopsia
- cant see which cars are parked or driving
- difficulties in following conversations
- insecure in social settings
what is the cornea
some of the light that hits the front surface of the eyeball is the transparent tissue at the front of each eye that plays an important role in focusing incoming light
what does vision operation begin with
light
what is light
light is produced by many objects in our surroundings and then reflects off other objects, and that reflection then launches the process of visual perception
what is lens
the transparent tissue located near the front of each eye that plays an important role in focusing incoming light. muscles control the degree of curvature of the lens, allowing the eyes to form a sharp image on the retina
what do the bipolar cells and ganglion cells make up
the optic nerve
what is the retina
the light-sensitive tissue that lines the back of the eyeball
what is an analogy of lens cornea and retina
the lens and the cornea focus on incoming light, just like a camera lens might, so that a sharp image is casts onto the retina
what do the rods and cones make up
the photoreceptors
what are the three main layers the retina is made up of
- rods and cones
- bipolar cells
- ganglion cells
what refracts the light
the cornea and lens refract the light rays to produce sharp, focused images on the retina
what are photoreceptors
specialized neural cells that respond directly to incoming light
what are rods
sensitive to very low levels of light and play an essential role whenever your moving in semidarkness
what are cones
less sensitive than rods and so need more light to operate at all. they are sensitive to colour differences
what photoreceptors are colour blind
rods. they can distinguish different intensities of light, but they provide no means of discriminating one hue from another
what do rods and cones do
they launch the neural process of vision from the back of the retina
where are cones most frequent
in the fovea. the number of cones drop off sharply as we move away from the fovea
what is the retina blind spot
position at which the neural fibres that make up the optic nerve exist in the eyeball
- no cones or rods here because the position is filled with fibres
how many types of cones are there
three
how is the perception of purple made
strong firing from only the cones that prefer short wavelengths, accompanied by weak firing from other cone types
what the visible spectrum
the narrow band of wavelengths between 700 (heat) and 360 (ultraviolet) nanometers
violet —> red
how is the perception of blue made
equal strong firing from the cones that prefer short wavelengths and those that prefer medium wavelengths, with other modest tiring by cones that prefer long wavelengths
what helps you perceive fine detail
cones
what is acuity
the ability to see fine detail, much higher for the cones than rods
what is the fovea
the very center of the retina, this is the region of the retina with the greatest acuity because it is filled with cones
where are rods in the fovea
prominent in the visual periphery, furthest from the fovea
what is the optic nerve
tracts leaves the eyeball and carriers information to a way station in the thalamus LGN
what is the lateral geniculate nucleus
an important way station in the thalamus that is first destination for visual information sent from the eyeball to the brain
what is lateral inhabitation
a pattern in which cells, when stimulated, inhibit the acuity of neighbouring cells
when is the message to the brain weaker
when the cell is less stimulated
what is edge enhancement
this process is of enormous importance, because its highlighting information that defines an object’s shape
what cells are stronger
the cells that detect the edge of the surface will be stronger than those that detect the middle
what begins immediately in the eyeball
the steps of interpretation and analysis of the brain
what is mach bands
a type of illusion in which one receives a region to be slightly dark if it is adjacent to a dark region
what are bipolar cells
receive input from photoreceptors and transmit their output to the retinal ganglion cells
what is single cell recording
this is a procedure through which investigators can record, moment by moment, the pattern of electrical changes within a single neuron
what is the center-surround cells
a type of neuron in the visual system that has a donut-shaped receptive field. stimulation in the center of the receptive field has an effect on the cell; stimulation in the surrounding ring has the opposite effect
how can you figure out what makes cells fire more or less
spikes per second
what is the receptive field
the size and shape of the area in the visual world to which that cell responds
what happens if the center and surronding cells fire at the same time
they will fire neither more nor less than usual
what are edge detectors
when the cell fires at their maximum only when a stimulus containing an edge of just the right orientation appears
what do preferences have to do with cells
the further away the cell is from its preferred orientation, the weaker the firing will be, and the edges sharply different from the cell’s preferred orientation will elicit virtually no response
what does the visual system rely on
a divide-and-conquer strategy, with different types of cells located in different areas of the cortex
what is Area V1 (vision)
the site on the occipital love where axons from LGN first reach the cortex
what do neurons in Area MT have (motion)
they have their own function; they are acutely sensitive to direction and speed of movement
what is parallel processing
many different steps going on simultaneously
what is serial processing
contrasted with parallel processing, in which each step is carried out one at a time
what is the advantage of simultaneous processing
speed and the possibility of mutual influence among multiple systems
what is the what system
some activation from the occipital lobe is passed along to the cortex of the temporal lobe. this system plays a major role in the identification of visual objects, telling you whether the object is a cat, an apple, or whatever
what cortex is apart if the what system
the inferotemporal cortex
what is the where system
some information gets passed down from the occipital lobe from a second pathway leading to the parietal lobe. this system guides your actions based on your perception of where objects are located
what cortex is apart of the where system
the posterior parietal cortex
what is visual agnosia
the inability to recognize visually presented objects
what is binding problem
the task of reuniting the various elements of a scene, elements that are initially addressed by different systems in different parts of the brain
what is spatial position
parts of the brain registering the cups shape is separated from the parts registering the colour or motion
what is neural synchrony
if the neurons detecting a vertical line are firing in synchrony with those signalling movement, then these attributes are registered as belonging to the same object and if they aren’t in synchrony then the features arent bound together
what are special rhythms
identifying which sensory elements belong with which
what is attention
plays a key role in binding otgether the seperate features of a stimulus
what is conjunction error
when we overload perceived attention, they correctly detect the features present in a visual display but then make the mistake of how the features are bound together
what is reversible (ambiguous) figure
people perceive it first one way and then another
what is figure/ground organization
the determination of what the figure is and what is the ground
what is a gestalt principle
a small number of rules that seems to govern how observers organize visual input, grouping some elements better but perceiving other elements to be independent of another
what did gestalts argue
the perceptual whole is different from the sum of its parts
perception is guided by proximity and similarity
it is within the visual scene you see elements that are close to each other or elements that resemble each other, you assume these elements are part of the same object
what are visual features
the elements of a visual pattern, verticle lines, curves, diagonals etc
what might perception be divided into
information gathering step or interpretation steps
- this is wrong
how is perception ACTUALLY divided
your interpretation of the input happens before you start cataloguing the inputs basic features, not after
what comes before the features
interpretation
what is perceptual constancy
the fact that we perceive the constant properties of objects in the world even though the sensory information we receive about the attribute changes whenever our viewing circumstances charge
what is size constancy
you correctly perceive the sizes of objects despite the changes in retinal image size created by changes in viewing distance
what is shape constancy
you correctly perceive the shapes of objects despite changes in the retinal image created by shifts in your viewing angle
what is bright constancy
correctly perceiving the brightness of objects whether they’re illuminated by dim or stong light
what is the inverse relationship between distance and retinal image
if an object doubles its distance from the viewer, the size of its image is reduced by half and if an object triples its distance, the size of its image is reduced by a third
what is unconscious inference
the hypothesized steps that perceive follow in order to take one aspect of the visual scene
how are retinal images seen
further objects cast smaller retinal images and closer objects cast larger retinal images
what is the contrast effect
the central square in this figure is surrounded by dark squares and the contrast make the central square look brighter and the square marked at the edge of the checkerboard, however is surrounded by white squares, which makes the marked square look datker
what are distance cues
features of the stimulus that indicate the position of an object
what is binocular disparity
the fact that your eyes look out on the world from slightly different positions; each eye has a slightly different veiw
what is monocular distance cues
perceives depth with one eye closed. it depends on the adjustment that the eye must take in order to see the world clearly
what are pictorial cues
an impression of depth on a flat surface within a picture
what is interposition
the blocking of your view of one object by some other closer object
what is liner perspective
the pattern in which parallel lines seem to converse as they get farther and farther from the veiwer
what is motion parallax
the projected images of nearby objects move more than those of distant ones, and this patter of motion in the retinal images gives you another distance cue
what is optic flow
a different cue relies on the fact that the pattern of stimulation across the entire visual field changes as you move forward. plays a large role in coordination of bodily movement
what is ocular dominance
relaying on one eye far more than the other one
