Keywords Test1

Question 1

Perception as an active process

Answer 1

We make unconscious inferences that are cognitively impenetrable based on sensory information

Question 2

Perception as an unconscious inference

Answer 2

Interpret 3D pictures as 3D objects, process faces holistically

Question 3

Inverse problem in perception

Answer 3

Perceived brightness and image can come from an infinite number of illumination combinations and shapes. The visual system must infer what it is

Question 4

Cognitive impenetrability of perception

Answer 4

Cannot be penetrated by knowledge

Question 5

Blind spot and filling in

Answer 5

No photoreceptors at the optic disk, there is a blind spot. Our brain fills in the gaps.

Question 6

Various psychophysical methods

Answer 6

Method of adjustment
Observers adjust stimulus level until they response change from seen to not seen or vice versa
Method of limits
Gradually decrease/increase stimulus level until observers report change from seen to not seen or vice versa.
Method of constant stimuli
Show different stimulus levels in random order repeatedly; for each level tally number of “yes” responses

Question 7

Threshold in psychometric curves

Answer 7

The curve starts at chance, the threshold is the steepest part of the curve, generally halfway between chance and 100 percent

Question 8

Absolute vs relative thresholds

Answer 8

Absolute threshold
The minimum stimulus intensity that can be perceived
Relative threshold
The minimum difference between stimulus intensities that can be perceived

Question 9

Weber vs Fechner laws

Answer 9

Weber = relative threshold is proportional to background level
Fechner= two signals that are just noticeably different are separated by one unit of perceptual/internal response

Question 10

Signal detection theory

Answer 10

Two factors that influence performance = signal and judgement.

Question 11

d’

Answer 11

When the distributions are further away d prime is larger, more likely true positives
When the distributions are narrower d prime is larger to
When the distributions are entirely overlapping d prime is zero
D prime is a measure of sensitivity. Tells you how well hits can be distinguished from false alarms
D does not depend on criterion

Question 12

false positive/negative

Answer 12

False positive -> test says yes when really no

False negative -> test says no when really yes

Question 13

Characteristics of foveal vs peripheral vision

Answer 13

Fovea is clearer. Peripheral is mainly rods and is better in lower light.

Question 14

Rods vs cones and their pathways

Answer 14

Rod: low light vision, no colour, low detail
Cone: Bright light vision, colour, high detail
Many rods to one ganglion, cones more one to one. Cone path is precise because info on which cone is activated is preserved. Rod cannot tell where photons come from because identical response for differing stimulations.

Question 15

ON/OFF-center cells in retina/LGN

Answer 15

Gets excited if light is in the on region only, gets inhibited if light is in the off region only, if both lit then cancelation from lateral inhibition

Question 16

Parvo vs magno cells/pathways

Answer 16

Parasol cells get inputs from many photoreceptors, poorer spatial resolution, respond faster to moving stimuli. Midget cells get inputs from fewer photoreceptors, higher spatial resolution but slower processing. More midget cells

Question 17

Retinotopic map in V1

Answer 17

Ganglion cell axons from the retina preserve their order in LGN. Parvo (small) LGN cells get inputs from (small) midget ganglion cells. Magno (large) LGN cells get inputs from (large) parasol ganglion cells.

Question 18

Cortical magnification in V1

Answer 18

Central 5° of visual field takes up 40% of V1

Question 19

Columnar organisation in V1

Answer 19

cells sensitive to neighboring orientations are located next to each other. cells are organised systematically based on eye of origin.
First cell = -45 then the whole columns will be for aspects of -45

Question 20

Simple cells in V1

Answer 20

Respond selectively to lines or bars in particular orientations with separate ON and OFF regions. They can be monocular or binocular. They are sensitive to length (bigger response with increasing line length up to a point)

Question 21

Complex cells in V1

Answer 21

Like simple cells, complex cells are orientation selective and are sensitive to length. But they are mostly binocular and have no separate ON/OFF regions. They are sensitive to length (bigger response with increasing line length up to a point)

Question 22

Hypercomplex cells in V1

Answer 22

Like complex cells except they obey end-stopping rule: increase response as line gets longer up to optimal length then decrease response if line gets longer still.

Question 23

Ventral pathway goes to the temporal lobe, down from V1

Answer 23

Allows us to recognise shape, size, objects, faces, and words.
Terminates in medial temporal lobe, hippocampus, amygdala.
Contributes mostly to visual recognition, memory, emotion.

Question 24

Dorsal pathway goes to the parietal lobe, up from V1

Answer 24

Handles aspects of the spatial layout such as location, distance, relative position, position in egocentric space, and motion.
Route feeds into motor cortex in frontal lobe.
Contributes mostly to visually-guided action and attention

Question 25

Identification of secondary visual areas

Answer 25

Physiology. Cells in different areas handle different visual attributes (motion in MT, colour in V4, objects in IT, etc.).
Architecture. Cytoarchitecture (cell size, cell density, number of layers, density of axons, etc.) can differ between visual areas, helping to identify distinct brain regions.
Connection. Revealed using chemical tracers that are picked up by cell bodies or axon terminals.
Topography. Each of the early visual areas contains a retinotopic map of visual field.

Question 26

Physical vs illusory contour in V1 and V2

Answer 26

Illusory contours begin in V2, about what you perceive no longer the physical stimuli

Question 27

Lateral inhibition and luminance level

Answer 27

Retinal ganglion cells don’t care much about uniform fields, what they care about (and enhance) are borders and edges

Question 28

Dark adaptation and rod/cone break

Answer 28

Rods and cones change their sensitivity when we move from a well-lit area to a dark place. Cones are more sensitive for 10 mins then rods take over. After 30mins that’s the best you will get.

Question 29

Hermann-Grid spots, Mach bands, Koffka ring illusions

Answer 29

On cell at the intersection will produce a smaller response than an on cell elsewhere, you see it as being darker because of the difference in activation
Receptive fields at boundaries are excited/inhibited differently than those within a band.
Continuous object cue wins over the other cues

Question 30

Colour matching/mixing experiment

Answer 30

The observer must mix three wavelengths of light to match the colour of the test light

Question 31

Opponent vs trichromatic theory of colour

Answer 31

Trichromatic Theory
percentage of light absorbed by each cone, 3 cones cover the whole spectrum. Colour perception is comparison of response of each cone. These ratios stay the same even if light intensity changes therefore colour is constant
Opponent process theory
3 opponent mechanisms, responding in opposite direction to different wavelengths.

Question 32

Tilt aftereffects and orientation-specific channels

Answer 32

Cause a tilt in the other direction, specific orientation neurons get tired

Question 33

Gestalt cues for perceptual grouping

Answer 33

Segmentation i.e. figure ground separation

Grouping: Proximity, similarity, continuity, closure

Question 34

Spatial frequency and fourier analysis

Answer 34

Representing images by sine waves. Only need to know frequency, contrast, orientation, phase

Question 35

Spatial frequency and hybrid images

Answer 35

See one at a time, will not see both together, higher effect if physical stimuli rather than just perception

Question 36

Contrast sensitivity function

Answer 36

Humans are most sensitive at 6-8 cycles/degree (about 12 black/white stripes in a thumb at arm’s length); gradually less sensitive to lower/higher frequencies. The highest frequency you can see defines your visual spatial acuity.

Question 37

Various monocular cues to depth

Answer 37

Occlusion
Texture
Shadow casting
Aerial view
Shading and contour
Linear perspective
Motion Parallax

Question 38

Retinal/binocular disparity and correspondence problem

Answer 38

Difference in image location of an object on left and right eyes because of the eyes’ horizontal separation
What features or objects in the retinal images come from the same real world objects

Question 39

Random dot stereogram

Answer 39

Shows that depth can be computed without other cues (e.g., perspective, motion parallax) and that binocular fusion can happen before form/object is perceived.

Question 40

Horopter and crossed/uncrossed disparities

Answer 40

Imaginary surface that includes fixation and other locations in space that produce corresponding retinal points. At the Horopter disparity is zero.
All non-corresponding retinal points (crossed (negative)for near objects, uncrossed(positive) for far objects) produced by non-horopter locations

Question 41

Motion aftereffects

Answer 41

motion will transfer between eyes, opposite direction to motion

Question 42

Inflow vs outflow theory of motion

Answer 42

Inflow model compares retinal data to feedback from eye muscles; outflow model compares them to brain commands.

Question 43

Aperture problem and the role of V5/MT

Answer 43

Motion direction signal in early neurons with smaller receptive fields (e.g. V1) is ambiguous
A secondary or extra striate visual area that plays a major role in motion perception, especially in processing global motion information from local motion signals

Question 44

Motion extrapolation and tennis errors

Answer 44

more likely to make predicted error in direction of motion

Bottom patches appear shifted towards direction of motion.