LECTURE 3 - Perception (copy) Flashcards
1
Q
what is perception?
A
- ability to recognize and interpret information from the senses
- provides building blocks for our thinking and remembering
2
Q
what is mental imagery?
A
- we can imagine an object without seeing/hearing/touching
- this is made possible by perception
3
Q
what are some examples of ways that our brains fill in missing information?
A
- eyes fill in the blindspot from the retina for cohesive visions
- visual illusions take advantage of how our brains fill in information
4
Q
how does the blue/black, gold/white dress show us that perception is an active process?
A
- some people see one colour combination, some see the other, and some can switch between the two
- difference in perception is due to differences in our minds’ assumptions about lighting conditions
5
Q
what are bottom up processes?
A
- sensory input from receptors to the primary sensory cortex for that system
- input leads to sensation, detection of sensory signals and the beginning of perception
- transduction: conversion of physical stimuli into electrochemical signals used in neurons
6
Q
how does an image coming into our eye differ from reality?
A
when an image enters the eye, it becomes upside down and inverted
7
Q
where on the visual field are the hemispheres responsible for vision?
A
- both eyes get input from both sides of the visual field
- axons from the nasal half of each eye cross over to the opposite side
- each hemisphere receives input from the opposite visual field, but from both eyes
8
Q
what is the primary visual cortex? who discovered it?
A
- also called V1
- david hubel and torsten wiesel
- specialized for basic visual processes; orientation, spatial frequency, motion direction of light and dark patches
9
Q
after V1, how does visual information get processed?
A
- sent forward in the brain via feedforward connections to serve higher order functions
- perception of colour, motion, objects, faces
- part of bottom up processing
- areas in frontal, temporal, and parietal cortices interpret information to guide thought and action
10
Q
what are top down processes?
A
- knowledge and expectations that influence and enhance out interpretation of sensory input
- feedback connections resolve ambiguity of feedforward signals (bottom up processes) that are subject to multiple interpretations
- goes from more sophisticated brain areas to more basic areas to change how we view a stimuli
11
Q
what are some things that affect the way we perceive stimuli?
A
- context
- past experiences
- brain makes predictions
12
Q
what is an example of how context is top down processing?
A
- context shapes perception and facilitates object recognition
- when you read the image from left to right its ABC, but without context it could be A - 13 - C
13
Q
what is unconscious inference?
A
educated guesses about most likely interpretation based on visual clues
- coined by H v. Helmholtz
14
Q
what is the theory of predictive coding?
A
- the brain constantly generates predictions about the world
- expectations are constantly compared with and validated against incoming bottom-up signals
- predictions and expectations guide the mind to the most likely interpretation
15
Q
what is object segmentation?
A
- visually assigning the elements of a scene to separate objects and backgrounds
- hard problem for the visual system to solve
- bottom up cues like visual motion can help with this
- but bottom up cues can be insufficient for a computer to distinguish objects, suggesting we need top down processes as well
16
Q
what is figure-ground organization?
A
- a form of object segmentation where boundaries of objects are clearly visible, but
- it is unclear which side belongs to an object and which side belongs to the background
17
Q
what rules does the brain use to solve ambiguity in figure-ground organization?
A
rules for determining what the object is
- rule of enclosure: region surrounded by another
- rule of symmetry: more symmetrical region
- rule of convexity: bulging region (convex)
- rule of meaningfulness: meaningful region
- if we can assign semantic meaning to something, we are likely to label it as a figure
18
Q
how do we see things despite them being partially occluded by other objects?
A
- the brain fills in missing info, also called amodal completion
- we are able to follow moving objects when they are occluded by extrapolating their trajectory based on their motion path
19
Q
what is the inverse projection problem?
A
- 2D input has to be converted to a 3D representation
- multiple 3D representations are possible from a single 2D image
- top-down information (depth cues) is needed to disambiguate the possibilities
20
Q
how do depth cues help us see in 3D?
A
- binocular disparity: retinas of the two eyes receive slightly different images, the closer something is to you, the greater the difference between what your two eyes see
- binocular depth cues: calculate how close an object is to us based on the extent of disparity between the eyes
- monocular depth cues with one eye (pictorial cues) also help us see 3D; linear perspective, texture gradient, blur, shadow/shading)
21
Q
what other cues do observers use to solve the inverse projection problem?
A
- size constancy: we perceive an object as the same size even when its distance to us changes
- we use our experience to evaluate object size, then use object size to determine distance - motion parallax: the movement seen when the observer moves through a stationary environment
- the closer an object is, the faster it seems
22
Q
what is relative motion?
A
when stationary objects appear to move
23
Q
what is colour constancy?
A
our visual system factors in differences in illumination when perceiving colour so that we perceive the same colour regardless of illumination
24
Q
what is lightness constancy?
A
we factor in illumination conditions when perceiving the brightness of things
25
what is colour assimilation?
- the opposite of colour constancy
- the color of an area appears to take on the hue of nearby colours
26
what is object recognition and how can it be challenging?
- ability to match images to stored representations of them in the brain
- difficult because of variations in shape, orientation, and lighting conditions
- trying to decide if two images are of the same thing depends on familiarity
27
what is agnosia? what can it help researchers understand?
- the inability to recognize objects and to match them to correct categories and labels
- allows researchers to distinguish between early and late visual processes that contribute to object perception
28
what is apperceptive agnosia?
impaired early vision
- people cannot perform simplest visual feature task
- can't discriminate orientation, colour or motion
- suggests problems with bottom-up processes
29
what is associative agnosia?
impaired late vision
- people cannot name or categorize objects
- suggests difficulties with top-down processes
30
what is the view-based approach to enabling object recognition?
- we match images to representations that are like 2D pictures or templates
- a template is a representation that filly describes the shape of an object
- simple and easy for clearly defined objects like numbers
- can be done by machines
- difficult for natural images and real-world objects
31
what is the structural descriptions approach to enabling object recognition?
- object recognition is based on models that represent objects as sets of 3D parts standing in spatial relationships to each other
- models have a "vocabulary" of components that are combined to form an object
32
what are some pros and cons of the structural descriptions approach?
cons: slow, hard to learn, unnatural
pros: flexible, objects identified regardless of orientation, angle, illumination, etc
- more tolerant of image/object noise than view-based approach
33
do we process objects and faces holistically? meaning as a whole object at once
- experience helps shape the degree to which object recognition is holistic
- experts in certain areas tend to process associated objects holistically
- we are all face experts, so we process faces holistically
34
what research was done on how experts view objects holistically?
- all people had a specialized area for processing faces (fusiform area)
- face areas were also active when images of the area of expertise were shown
- FFA responds to non-face stimuli if they fall into the area of expertise
35
who is yasmin el-shamayleh and what did she discover?
- one of few racialized women doing research on primate object recognition using single-cell recordings and optogenetics
- found that each neuron represents a small part of an object and many neurons must work together to represent the whole object
- findings support the structural description approach to object recognition
36
what is mental rotation?
a type of mental imagery where we are able to compare and match rotated images
37
what is aphantasia?
condition where a person has an inability to form images in their mind
38
what are the two pathways for visual information after the primary visual cortex (V1) ?
1. dorsal pathway to posterior parietal cortex
2. ventral pathway to inferotemporal cortex
39
what is the dorsal pathway of vision responsible for?
"where" pathway, action pathway
- spatial orientation
- motion of objects
- attention
- uses perceptual info to guide ongoing actions
40
what is the ventral pathway of vision responsible for?
"what" pathway, perception pathway
- object recognition and colour
- supports many perceptual functions
41
what is the updated duplex theory of vision?
- visual system has two separate interacting components
1. one for perceiving object
2. one for controlling actions directed at the objects
- both streams use info for distinct purposes and analyze visual information separately
- they work together to produce adaptive behaviour
