Unit 2 Flashcards
the constructive brain
the brain actively constructs representation of world and makes assumptions about the world based on 3 things (light and shadows, cues to size and debt, and object structure); rules operate without conscious input and can cause optical illusions
cornea
- light passes through here, it is the eye’s thick, transparent outer layer
- it focuses incoming light, which then enters lens
iris
- band of muscle, determines eye’s color and controls pupil’s size
- accommodation is process where behind iris, muscles change shape of lens; flatten it to focus on distant objects and thicken it to focus on farther closer
pupil
- hole in eye where light is transmitted
- it is dark circle at the center of the eye, a small opening in front of the lens
- by contracting (closing) or dilating (opening), it controls how much light enters eye
retina
- light that is bent inward by the lens and is focused comes to retina, which is thin inner surface of back of the eyeball
- it contains sensory receptors that induce light into neural signals
what is light a part of
- part of electromagnetic radiation and visible light is only small part of spectrum (400 to 700 nanometers)
- color of light is determined by wavelengths of electromagnetic waves that reach eye
what are two types of photoreceptors
- rods (sensitivity)
- cones (acuity)
Rods (type of photoreceptor)
- able to detect light
- can see in low light conditions + night vision
- poor in fine detail
- located most in periphery
Cones (type of receptor)
- can see fine details
- used for reading and color vision
- concentrated on central region (forea)
Types of Cones
- according to trichromatic theory, color vision results from activity in 3 types of cones that are sensitive to different wavelengths
1. Blue: S Cones (small wavelength)
2. Green: M Cones (medium wavelength)
3. Red: L cones (long wavelength)
Fovea
- near retina’s center, where cones are densely packed in small region
- cones become increasingly scare near outside edge, rods are concentrated at retina’s edge
- no rods are in the fovea
color blindness
abnormal or missing cone type
Opponent Color Processing
- opponent process theory says that red and green are opponent colors to blue and yellow, is complement to trichromatic theory
- this describes the second stage of visual processing
- cone output converted to opponent pairs
ex: (red - green, blue - yellow, white - black)
Assumption #1: Light and shadows
Light comes from above (makes sense evolutionarily, with sunlight from above)
Assumption #2: Shadows have soft edges (??)
- Checker-Shadow Illusion (cylinder on checkerboard): A and B are the same shade of grey dispute appearing like 2 different ones, important to note that B would have to be much lighter in real world
Assumption #3: Cues to depth
- helps us transform 2D image on retina to 3D world
- 2 types of cues: binocular (two eyes) and monocular (1 eyes) (ex: occlusion, relative size + height, etc.)
Binocular depth cues
- available from both eyes together + present only when viewing 3D world
- provide internal cues about how far away something is
Monocular depth cues
- available from each eye alone + provide org info that can be used to infer depth
- emerge when we move through space + depend on relative changes to visual input with motion
Ponzo Illusion
- example of size illusion, it is the one of the train-track
- the lines appear to be the same size but appear different sizes
- in the real world, the top rectangle would have to be much larger
- depth cue: linear perspective
The Ames Room
- example of size illusion, of the trapezoidal room
- the twins standing on 2 sides of the room, one appears to be significantly larger than the other but the identical twins are the same size
- to see in person, can only look with one eye or than you can tell there is something wrong with it
Assumption 4: Generic Viewpoint
- unlikely to reflect accidental viewpoint
- Penrose Triangle: it is impossible w/ depth, only possible 2D
- picture of people holding up the Leaning Tower of Piza is forcer perspective photography
Object Completition
- completion is primitive and automatic
Kanizsa Triangle
- edges of “Pac-men” unlikely to align by choice
- triangle looks brighter than background
- edges unlikely to align by chance
- type of illusory contours
Gestalt grouping principles
- group of surfaces together
- unified perception from sensory stimuli
(1) proximity: closer two figures are to each other, more likely we are to group them and see them as part of same object
(2) similarity: tend to group figures according to how closely they resemble each other
(3) good continuation: tent to group together edges or contours that are smooth or continuous as opposed to those that are abrupt or have sharp edges
(4) closure: tent to complete figures that have gaps
~(5) common fate: w tent to see things that move together as belonging to same group
Rubin’s “face-vase” illusion
- example of segmenting figure and group
- vase with queen Elizabeth’s profile on one side and Prince Phillip’s profile on the other side, can see when against solid backdrop
- classic illustration distinguishing figure from group is reversible figure illustration
Assumption #5: Certainty over ambiguity
- happens especially with faces
- brain is looking at patterns, wants to know if something is out there
- pareidolia: looking for patterns in visual inputs
Face Inversion effect
- we are wired to see faces but efficient processing only happens for upright faces
- Thatcher illusion: see 2 faces upside down and look okay, when turn right side up, can see one is clearly disfigured
Hue
- consists of distinctive characteristics that place particular color in spectrum, depends primarily on light dominant wavelength when it reaches eye level
Saturation
- it is purity of color; varies according to mixture of wavelengths in stimulus
Lightness
- color’s perceived intensity; determined chiefly by amount of light reaching eye + could depend on background
object constancy
- perceive collection of sensory information as belonging to same object, object constancy leads us to perceive object as unchanging despite changes in sensory data the compose object
- for most part, changing object’s angle, distance or illumination doesn’t change our perception of that object’s size, shape, color, or lightness
- brain computes relative magnitude of sensory signals it receives rather than relying on each sensation’s absolute magnitude
- perceptual system ability to make relative judgements allows it to maintain constancy across various perceptual contexts
Prosopagnosia
- when someone has particular deficits in ability to recognize faces but not in ability to recognize other objects; this implies that facial recognition differs from non-facial object recognition
Binocular disparity
- cue that is caused by distance between human’s 2 eyes
- brain has access to two different but overlapping retinal images and uses disparity between 2 retinal images to compute distance to nearby objects
Convergence
- refers to way eye muscles turn eye inward when we are viewing object nearby
- to focus both eyes on close object, requires eye to converge more than if object is away
- brain knows how much eyes are converging through feedback from eye muscles and uses this info to perceive distance
occlusion
near objects block objects that are far away
relative size
far off objects project smaller retinal image than close objects do; if they are the same physical size
familiar size
because we know how large familiar objects are, can tell how far away they are by size of their retinal image
linear perspective
seemingly parallel lines appear to converge in distance
texture gradient
uniformly textured surface recedes, it texture continuously becomes dense
positive relative to horizon
all else being equal, objects below horizon that appear higher in visual fields are perceived as being farther away
motion parallax
- arises from relative speed with which objects move across retina as person moves
- because view of objects closer to us changes more quickly than does view of objects that are farther away, motion provides information about how far away something is
Stroboscopic movement
- perceptual illusion that occurs when 2 or more slightly different images are presented in rapid succession
- demonstrates that brain, much as it fills in gaps to perceive objects, fills in gaps in perception to motion
Motion aftereffects
- occurs when you gaze at moving image for a long time and then look at stationary scene
- experience momentary impression that new scene is moving in opposite direction from moving image
Change Blindness
- we think we perceive a rich detailed world but representation sparse
- we cannot attend everything to vast array of visual info available, often “blind” to large changes in our environment
- change blindness is a phenomenon of visual perception that occurs when a stimulus undergoes a change without this being noticed by its observer
Experiment for Change Blindness
- Simon and Levin: where experimenter in hard hand asked for directions, only 50% of participants noticed change but didn’t notice change in person
- in 1st experiment, professors didn’t notice at all compared to college students
- also depends on group membership (where stranger was easily categorized from being from a specific and different social group)
- goes to show we only perceive and remember basic gist; details are “seen” but are not identified or remembered
- in real life, visual environment is fairly stable as out there not much is changing
3 main points about attention
(1) attention involves selection: have to select information and responsible for things entering into conscious awareness
(2) attention selects for awareness
(3) attention has limited resolution: limits on selection space
ex: talking/having conversation at party: there are many going on but can only attend one conversation at a time
Dichotic Listening Task
- example of attentional selection
- where different messages are played into each eye
- subject “shadows” (repeats out load) one stream
- little of unattended input is recalled
Visual Shadowing Task
- example of attentional selection
- ex: pay attention to the team wearing the white shirts, count the # of times they pass the ball, many people fail to notice the gorilla that walks in the background
Negative priming (?)
- fate of unattended items due to inattentional blindness
Exceptions to the fate of the unattended
- some things just grab out attention (someone’s name, we have bottom up cues for perspective)
- “pop-out” of certain perceptual features (automatic exogenous, involuntary, attention: cannot be controlled or suppressed)
Endogenous Attention
- intentionally diverting of attention in way, some stimuli demand attention and virtually shut off ability to attend to anything else
- some stimuli, such as emotional stimuli that signal potential danger, may readily capture attention b/ provided important info
- Endogenous, or top-down, attention is a voluntary, sustained, goal-driven process
Exogenous attention
- when focus of your attention is driven by stimuli or event, being driven by external events/stimuli in environment
Conjunction search
- search for combination of simple features
- process is slow and serial
- must select each time in turn or much select each item in turn
- ex: where is the horizontal green T?
Spatial limits of attention
- visual crowding: difficulty recognizing objects in clutter
- coerce spatial recognition of attention
- difficulty reorganizing objects in clutter
Objects limits of attention
- Multiple object tracking (MOT): can only track 4 objects at a time, becomes much harder at higher speeds
Time limits of attention
- attentional blink: difficulty selecting 2nd target short time after 1st target
- ex: rapid display of letters go by, are told to say what letter comes after W, are able to recognize W in display, but most people miss what letters next as are still processing that W went by
- attentional selection takes certain amount of time, cannot be redeployed immediately
Heavy Media Multitaskers vs Light (LMM) (??)
- perceptual filtering
- task switching
- working memory
How can we improve attention?
- we can improve attentional through video games
- requires smaller attentional blink, improved object tracking but only certain games help
Understanding counsciousness
- mental systems that operate at unconscious level
- not due to motivation or suppressed trauma to avoid memories as Freud suggested
- Daniel Dennet: the “magic” of consciousness says that we see illusions not tricks,
Anosognosia
- Anosognosia is a neurological condition in which the patient is unaware of their neurological deficit or psychiatric condition
- ex: For example, someone with hemiplegia may not realize that one side of their body is weak or paralyzed. But they may still be aware of symptoms like difficulty speaking (aphasia) or loss of vision (hemianopia)
- single largest reason why people with schizophrenia or bipolar disorder refuse medications or do not seek treatment
qualia
- your subjective experience of sensation, meaning qualitative experiences of your conscious state
sleep deprivation + deficiency
- impaired concentration + decision making
- emotional irritability
- long term: increased risk of heart rate, diabetes
fatal familial insomnia
- happens later in life where individuals can no longer sleep
- insomnia followed in couple of years by dementia + more
- very rare prion disease
- causes atrophy of thalamus
- death happens between 1-2 years
how is sleep a conscious experience?
- sleep is an altered state of consciousness, still have some awareness of environment
- conscious experience of world turned off
- brain is still responding to some things out there in the environment
how do we quantify sleep?
- using electroencephalography (EEG)
- measures electrical activity in brain
- shows distinct stages of sleep