Chapter 3: Perception

Question 1

What are key aspects about this lecture in regards to visual perception?

Answer 1

-the visual system
-visual coding
-form perception
-constancy
-the perception of depth

Question 2

What is the pathway of light in the eye?

Answer 2

light —> cornea—>lens—->retina

Question 3

What is the role of the cornea and lens in light?

Answer 3

the focus light onto the retina

Question 4

What does the iris do to regulate pupil size and what is the effect?

Answer 4

-iris can open and close to regulate the pupil size and control the amount of light that reaches the retina

Question 5

What are the three main layers of the retina?

Answer 5

-photoreceptors (rods and cones)
-bipolar cells
-ganglion cells (axons that make up optic nerve)

Question 6

What is the impulse pathway in the eye for light?

Answer 6

-photoreptors—> bipolar cells —–> ganglion cells —> optic nerve —-> LGN in thalamus —-> V1

Question 7

What is the sensitivity to dim light of rods and cones?

Answer 7

rods - sensitive to dim light
cones - cannot function in dim light

Question 8

What is the acuity of rods and cones?

Answer 8

rods —> lower acuity
cones —-> higher acuity

Question 9

What is the color sensitivity of rods and cones?

Answer 9

rods —> color blind
cones —–> color sensitive

Question 10

What is the location of rods and cones in the eye?

Answer 10

rods - around the fovea in periphery
cones - in or near the fovea none in the periphery

Question 11

What are the three types of cones?

Answer 11

short, medium, and long wavelength - have wavelengths corresponding to different color hues
short is violet and blue
medium is green
and long is red and orange

Question 12

What is edge enhancement?

Answer 12

it is produced by lateral inhibition and it helps us to perceive the outline that defines an objects shape

Question 13

What is lateral inhibition?

Answer 13

the capacity of an exited neuron to reduce the activity if its neighbors
-cell b is more inhibited than cell c despite receiving the same degree of stimulation

Question 14

What is single cell recording?

Answer 14

-provides knowledge about the visual system
-neuron firing rates recorded when different stimuli are presented to identify what stimulus characteristics influence firing
-each cell in the visual cortex has a receptive field - size and shape of the area in the visual world to which that cell responds

Question 15

What cells have center surround receptive fields?

Answer 15

bipolar cells ganglion cells and cells in the LGN

Question 16

What is a center surround receptive field?

Answer 16

a stimulus in the center of the receptive field leads to a faster firing rate
-a stimulus in the surrounding area of the receptive field leads to slower and below baseline firing rates
-a stimulus covering the entire receptive field has the same effect as no stimulus

Question 17

In what cells are edge detector receptive fields found?

Answer 17

primary visual cortex

Question 18

What are edge detectors receptive fields?

Answer 18

these detectors fire when a stimulus within the receptive field contains an edge of a particular orientation
-the less the edge is like the cells preferred edge the less often it fires

Question 19

What are the types of receptive fields?

Answer 19

-other receptors specializations
-angles, motions and direction, and corners

Question 20

What is parallel processing in the visual system?

Answer 20

different neurons in area V1 are specialized and this results in parallel processing rather than serial processing - have a divide and conquer

-from the retina to V1 have serial processing but from V1 beyond the processing becomes parallel as different neurons in V 1 process different components of the image: lines of different angle, corners, coiors, movement

Question 21

What are advantages of parallel processing?

Answer 21

speed and efficiency
mutual influence among distinct processing areas
-interpretation of an objets motion depends on understanding of the objects three dimensional shape
-objects three dimensional shape depends on your understanding of its motion
-since both sorts of analysis go on simultaneously each type of analysis can be informed by the other

Question 22

What is the what system of ventral visual stream?

Answer 22

-identification of the visual objects
-occipital-temporal pathway
-damage: can lead to visual agnosia

Question 23

What is the where system of the dorsal visual system?

Answer 23

-location of visual objects and guiding of actions
-occipital parietal pathway
-damage: can lead to problems with reaching for seen objects

Question 24

What is the third pathway that begins in the primary visual cortex?

Answer 24

it starts in V1 and projects into the posterior banks of the superior temporal sulcus via the motion selective area V5/middle temporal MT
-the sts compute the actions of moving faces and bodies and shows the third pathway is specialized for social perception

Question 25

What is the binding problem?

Answer 25

parallel p[rocessing splits up the problem ----> but we do not see the wrold as disjointed ----> this leads to the binding problems

Question 26

What are some elements that help solve the binding problem?

Answer 26

-spatial position - overlap map of what forms are where with maps of what colors are where and so on -neural synchrony - the brain seems to register synchronized firing as a cue that the attributes belong to a single object -attention - in the absence of attention conjunction errors are common

Question 27

How is attention critical for binding visual features?

Answer 27

-conjunction errors -people with attention deficits are particulalry impaired at judging how features conjoin -neuronal firing becomes synchronized for attended stimuli but not for unattended stimuli

Question 28

What is the necker cube?

Answer 28

example of form perception -we need to go beyond presented to process visual info -a reversible or ambiguous figure -one set of visual features resulting in multiple interpretations -only one interpretation visible at a time

Question 29

What is an example of a type of form perception illusion?

Answer 29

neutral figure ground organization - knowledge can change our interpretation

Question 30

What is an example of a type of gestalt principle illusion?

Answer 30

many stimuli are ambiguous not only reversible

Question 31

What is the gestalt principle?

Answer 31

the human mind and behavior as a whole rather than try to break it up into parts -our ability to interpret ambiguous scenes is governed by a few basic principles -similarity - tend to group these dots into columns rather than rows grouping dots of similar colors -proximity - tend to perceive groups linking dots that are close together -good continuation - we tend to see a continuous green bar than two smaller rectangles -closure - tend to perceive an intact triangle than open figures -simplicity - tend to interpret a form in the most simple way possible -with good proximity closure and continuation we can perceive letters and words easier

Question 32

What are the multiple activities going on in parallel in perception and which one goes first?

Answer 32

-information gathering -interpretation -neither step in the perceptual process goes first

Question 33

What is perceptual constancy?

Answer 33

-we perceive constant object properties like sizes shapes even though sensory information about these attributes change when viewing circumstances -brightness constancy -size constancy -shape constancy -color constancy

Question 34

What is shape constancy?

Answer 34

correct perception of an objects shape despite changes in its shape on the retina

Question 35

What is brightness constancy?

Answer 35

when you correctly perceive the brightness of objects whether they're illuminated by dim light or the strong sun

Question 36

What is size constancy?

Answer 36

when you correctly perceive an objects size despite the changes in retinal image size created by changes in viewing distance

Question 37

What helps dictate size constancy?

Answer 37

-influenced by relationships between objects in the visual field that stay the same regardless of your viewing distance

Question 38

What is unconscious inference?

Answer 38

-relationships alone are insufficient distance cues also contribute to constancy -actual size = retinal image size * distance

Question 39

What is the role of interpretation in illusions?

Answer 39

its role in perception becomes clear from the misinterpretation of illusions

Question 40

What is the role of binocular disparity in the perception of depth?

Answer 40

-we need to know distance to be successful at size judgements - distance cues - binocular disparity difference between each eyes view - this helps when objects are withing 30ft otherwise further than that both eyes see the same image

Question 41

What are monocular distance cues?

Answer 41

lens adjustment pictorial cues like interposition linear perspective texture gradients

Question 42

What are some examples of motion being another distance and depth cue?

Answer 42

motion parallax - pattern of motion in the retinal images optic flow - as you move towards or away from an object