Chapter 4: Perception Flashcards
sensation
registering stimuli energy and transmitting it to the brain
perception
processing sensory information into something that can meaningfully guide behaviour
where does perception take place
in the brain
Proprioception
the sense of where in space our limbs are
Nociception
the sense of pain due to bodily damage
Equilibrioception
the sense of balance
lightness
our perception of how light or dark something is
what surfaces tend to be lighter
More light reflecting into the eye tends to be a lighter surface
our perceptual brain is most concerned with what properties
the properties of an object that remain stable overtime
does our perceptual image change
Our eyes are constantly moving and thus our perceived image is constantly changing
perception often depends on ____
guesses
bi-stable stimuli
stimuli where the brain changes its mind upon looking at them
eye
an organ whose purpose is to gather light, focus it, and turn it into a neural signal
cornea
a transparent, rubbery layer of tissue at the front of the eye that bends light to help it land on the correct part of the back of the eye
iris
a circular ring of coloured muscle that light passes through after the cornea
pupil
the small opening in the iris that light passes through
path of light in the eye
Light -> cornea -> pupil -> lens -> back of the eye
focus
light from specific locations hits specific parts of the retina
perspective projection
objects that are farther away produce a smaller image than those that are close by. occurs because light must pass through a small point
how is the image projected on the retina oriented
upside down because light from above falls on the bottom of the retina while light from below falls on the top of the retina
retina
consists of multiple layers of neurons with the last layer containing photoreceptors
photoreceptors
light-sensitive neurons
two types of photoreceptors
rods & cones
rods
- sensitive photoreceptors that require less light to be stimulated
- Better for seeing in the dark
- Reduced resolution
- Respond equally to different wavelengths of light
- Located in the periphery of the retina
cones
- less sensitive photoreceptors that require more light to be stimulated
- Better for seeing in well-lit conditions
- High resolution
- Come in 3 different varieties that respond differently to different wavelengths of light
- Located in the fovea (centre of the retina)
optic nerve
a bundle of axons that pass from the retina to the brain
lateral geniculate nucleus
part of the thalamus that receives 90% of visual information from the retina
thalamus
part of the brain that serves as a waystation between sensory inputs and the cortex
primary visual cortex (V1)
the first part of the visual cortex where neurons respond to fairly simple patterns consisting mostly of oriented edges
middle cortex (V2)
the second part of the visual cortex where neurons respond to complex shapes
late cortex (V3)
the third part of the visual cortex where neurons respond to specific objects
visual agnosia
cases in which a person has difficulty recognizing or perceiving one kind of visual stimulus, while maintaining the ability to process other kinds of stimuli
prosopagnosia
a marked difficulty in recognizing individual faces
semantic agnosia
a marked difficulty in recognizing everyday objects such as tools
fusiform face area (FFA)
a particular region of the temporal cortex that shows greater activity when people engage in a facial recognition task
lateral occipital cortex (LOC)
a particular region of the occipital lobe that is selectively activated when people to an object recognition task
Greebles study
challenged that the FFA is specialized to process faces and concluded that it is rather responsible for visual expertise
dorsal stream
(where stream) takes information from the occipital to parietal lobes. Responsible for perceiving location, space, movement information
ventral stream
(what stream) takes information from the occipital to temporal lobes. Responsible for perceiving shape, size, visual details
alternative explanation for ventral and dorsal streams
What/ ventral corresponds to perception
Where/ dorsal corresponds to action
image segmentation
the retinal image is a continuous array of measurements but the brain wants to know how to divide it up into different objects and regions
depth perception
the retinal image is in 2D but the brain wants to know where the objects are in 3D
object recognition
the brain wants to identify what the objects are
bottom-up processing
the processing of the stimulus that does not require any specific knowledge of it
top-down processing
where specific knowledge about a particular stimulus contributes to how it is perceived
what is most important for image segmentation
Points in the image where there is a sudden change from dark to light or vice versa
figure-group assignment
Determines which regions of an image contain the objects and which contain the continuous background that the objects are in front of
3 cues the brain uses when deciding which region to assign a border to
convexity, symmetry, smaller region
law of similarity
the tendency to group together features of the same image that have similar properties in some dimension
law of proximity
the tendency to group features of the image that are close together
law of good continuation/ contour
the tendency to group together features that form a smooth, continuous path
what type of processing is depth perception
bottom-up
cues to depth perception
occlusion (blocking), motion parallax, binocular disparity
motion parallax
objects farther away from you will change their position more slowly on your retina as you move
binocular disparity
the difference in position on the retina of each eye
recognition
Determining what objects are by matching some incoming stimulus to a stored representation in memory
template model of recognition
matching an object to an image stored in memory point by point
template model of recognition in the real world
fails because everytime you view an object, it produces a different image
identification
the ability to identify the same object across variations
classification
recognizing something as a member of a category even if you haven’t encountered that specific example before
scene schema
people learn which objects tend to appear in particular contexts
exteroception
the sensing and processing of information from the external environment by the 5 basic senses
interoception
the sensing and processing of information inside the body
phonemic restoration effect
a perceptual phenomenon in which missing sounds are filled in by the brain based on our knowledge of language
purpose of the auditory nervous system
to transmit properties of sound waves and transduce them into neural signals
pinna
the visible portion of the ear made up of folded cartilage. Its purpose is to capture the sound in the air and transmit it to the ear canal
ear canal
a narrow tube that amplifies certain frequencies and transmits the sound to the eardrum
eardrum
a thin piece of tissue separating the ear canal from the inner ear. It amplifies certain frequencies and passes them to the ossicles
ossicles
a series of tiny bones that ensures the appropriate frequencies and amplitudes are relayed to the cochlea
cochlea
a coiled, bony structure in the inner ear that is filled with fluid
basilar membrane
a strip of tissue in the cochlea that contains hair cells
hair cells
mechanoreceptors that are moved by vibrations in the fluid in the cochlea. they transduce the mechanical signal into an electrical signal in response to the basilar membrane vibrating
tonotropic map
a spatial arrangement of neural structures in which locations are organized based on the frequency of the sound they encode. High frequencies make the wider part vibrate and lower frequencies make the narrower part vibrate (like a xylophone)
As you go further along the coil, the frequency hair cells respond to gets ____
lower
where does tonotropic organization stop
once it reaches the auditory cortex
primary auditory cortex (A1)
a region in the temporal lobe that is the first to receive auditory information from the cortex
what are the main streams of hearing?
Divided into the dorsal & ventral streams, where the dorsal is involved in sound localization and the ventral in sound identification
sound waves
oscillating movement in the air caused by vibrations of objects in the air
frequency (wavelengths)
the distance between the crests of sequential waves
amplitude
the height from the trough of the wave to its crest
amplitude is an indication of
loudness (high amplitude= loud)
olfaction
the sense of smell, which is concerned with measuring chemicals that have travelled through the air
gustation
the sense of taste, which is concerned with measuring the presence of certain chemicals that have been ingested into the mouth
what senses are most involved in cognition?
sight & hearing
what senses evolved first
chemical senses (gustation & olfaction)
taste buds
structures on the surface of the tongue that contain the sensory receptors for taste
what are the basic taste receptors & how do they work
5 basic taste receptors: sweetness, sourness, saltiness, bitterness, and savouriness (umami). Chemicals in the mouth bind to the taste receptors, leading to changes in electrical potential and neurotransmitter release. These sensory neurons send their signal through the brainstem
primary gustatory cortex
the first region of the cortex to receive information from the gustatory sensory system
olfactory epithelium
a strip of tissue in the nasal cavity that contains the chemical sensory receptors that support smell
does smell or taste have more sensory receptors?
smell
olfactory bulb
a specialized structure at the bottom of the forebrain that receives information from the olfactory epithelium
where does information go after the olfactory bulb?
Projects to several other brain structures including the amygdala and hippocampus
somatosensory cortex
a region of the brain located in the temporal lobe that receives multiple sources of sensory information from across the body, including the sense of touch
cortical homunculus
a spatially organized map of the human body contained within the somatosensory cortex that processes touch information
how is the cortical homunculus organized?
The representation is enlarged for parts of the body that are dense with sensory receptors
constructive perception
a model of perception in which sensory information is used to generate a mental model of the environment that is assumed to have caused the sensory stimulus
direct perception
a theoretical approach to perception that holds that the sensory stimuli be used to guide behaviour in an action/perception loop
who is direct perception associated with?
Associated with James J. Gibson & Johannes Muller, who proposed that individual nerves formed pathways that led directly from sensation to behaviour
stereopsis
the use of binocular disparity in perceiving depth
What type of processing is often involved in recognition?
top-down
dancers and interoception study
Christensen et al., 2017: Dancers have increased interoceptive accuracy
They could estimate their heart rate more accurately than non-dancers, which was unrelated to fitness levels or counting ability (nuisance variables)
Synaesthesia
A neurological condition, with some genetic component, in which one sense automatically triggers the experience of another sense
grapheme-colour synesthesia
a person sees colours with certain letters or numbers
main hypothesis for synaesthesia
that it is due to cross-wiring between processing areas in the brain
synaesthesia in artists
Artists are 8x more likely to have synesthesia than non-artists because the cross-talk between sensory areas increases the ability to think creatively and in metaphors
getting from sensation to perception
Stimuli are registered by a sensory receptor, which are transduced into a neural impulse. The code is then transmitted by the brain through subcortical regions to generate perception and behaviour
McGurk effect
A multisensory illusion such that there is a change in auditory perception from visual perception
takeaways from the McGurk effect
Demonstrates that there is an integration of sensory information & that visual input is dominant
parts of the early visual processing system
eyes and the optic nerve
parts of the late visual processing system
the visual cortex (occipital lobe)
early visual processing steps
- Light waves enter the eye and are focused, inverted, and projected by the cornea and lens onto the retina
- Photoreceptors in the retina convert light to electrical activity
- The electrical signal is sent to bipolar cells and then to ganglion cells
- The signal exits through the optic nerve to the brain
information compression
Millions of photoreceptors in each retina converge onto 100 x fewer ganglion cells -> optic nerve -> brain
what part of the visual field is most detailed
the centre
perceptual filling in
later visual processing systems fill in what the periphery should be perceiving based on information from the surrounding areas
where are photoreceptors located in the retina
at the back
where are ganglion cells located in the retina
at the front
what is the optic nerve made up of
the axons of ganglion cells
blindspot
the location where the optic nerve leaves the brain and there are no photoreceptors so visual stimuli are not received
principle of contralateral representation
The left visual field is perceived via the right hemisphere
The right visual field is perceived via the left hemisphere
visual association area
interprets visual information and assigns meaning
ventral damage with intact dorsal stream
results in impaired performance on visual object recognition or matching tasks
dorsal damage with intact ventral stream
results in impaired performance on visually guided action (picking up an object appropriately)
pain perception study
Jepma et al., 2018: individuals had significantly pain ratings for high vs. low cue trials even though the level of shock was exactly the same, demonstrating that pain perception is partly determined by expectations
the Ponzo illusion
two equal lines are placed on a railroad track and the top line looks bigger because of our previous assumptions about depth cues
the monster illusion
one monster is chasing another and the one at the back appears much larger because of depth cues
the visual illusions we are susceptible to demonstrate
the prior assumptions we have
ames room
a functional illusion where expectations of observation guide perception. In a trapezoidal room, one person will look much taller than the other even if they’re the same size because of our assumptions about size constancy
the letters in context effect
the ability to read words in sentences even when the letters are mixed up because of our assumption of context effects
the colour in context effect
the context a colour appears in can influence how you see that colour because of our assumption of context effects
colour perception depends on
the wavelengths of light that all on our retina & our past experiences of how objects look under different contexts of illumination
the munker-white illusion
we see two columns that are the same colour as different because of their surroundings. Demonstrates the colour in context effect
the rotating snake illusion
we perceive motion when there isn’t because of peripheral drift
compensation of visual fields
The left and right visual fields can compensate for each other’s blindspot
where does the optic nerve of each eye transmit information?
to both hemispheres in the thalamus
necker cube
an example of a bi-stable stimuli that demonstrates that our perception often depends on guesses
visual experience of blindsight patients
No conscious awareness (explicit perception) of visual objects in their damaged visual field. Able to implicitly respond to questions about objects presented in the damaged visual field, which suggests they can perceive something without consciousness
what do blindsight experiements demonstrate about consciousness?
Perception is first processed without conscious awareness in the brain
tests of blindsight
Over trials, turn a light on or off in the blinded visual field. Ask patients to guess if the light was on or off (forced-choice responding task). Patients performed above chance on the forced-choice responding task for lights in the blinded area
critiques of blindsight experiments
- There may be other pathways for visual information to bypass the PFC
- Relies on self-report
- Some blindsight cases report a non-visual feeling that something happened
blindsight and visual imagery
Blindsight leads to deficits in consciously processing incoming visual information but not imagery
damage to the dorsal stream can lead to what conditions
akinetopsia & optic ataxia
akinetopsia
the inability to perceive motion; the person instead sees motion as a series of stationary objects
optic ataxia
the inability to estimate movements or directions of objects in space
damage to the ventral pathway can lead to what conditions
visual agnosias
visual agnosia
Difficulties recognizing objects
what is the cause of visual agnosia
damage to the lateral occipital cortex
prosopagnosia
the fusiform face area (FFA) damage leads to selective deficit in recognizing faces, keeping intact the ability to visually recognize other objects
Patient WJ
a sheep farmer with prosopagnosia who was unable to name or recognize famous faces or determine age or gender or human faces but could recognize and discriminate sheep with very high accuracy. he demonstrated that there is selective face processing in the brain
apperceptive visual agnosia
A failure in recognizing objects due to problems with perceiving elements of the objects as a whole
what kind of tasks to people with apperceptive visual agnosia struggle with?
tasks involving perception and discrimination of objects
associative agnosia
An inability to associate visual input with meaning
what kinds of tasks do people with associative agnosia stuggle with
tasks involving accessing informaiton from memory
what kind of agnosia does a patient who can’t copy an image but can draw it from memory have?
apperceptive visual agnosia
what kind of agnosia does a patient who can’t draw an image from memory but can copy it have?
associative agnosia
bistable figures
Ambiguous sensory data with multiple valid interpretations. The brain relies on various cues to determine how to perceive the stimuli
Gestalt approach to perception
state that the whole that is perceived is greater than the sum of its parts
what type of processing does the Gestalt approach subcribe to?
top-down processing
two main gestalt principles
principle of experience and the visual grouping principle
principle of experience
we see what we are familiar with
how does the brain decide what to perceive as a figure and what to perceive as ground?
We are more likely to perceive something as a figure if it’s something we’re familiar with
principle of closed forms
we see a shape in terms of closed forms, and we like to see items that enclosed as a whole
what is the main gestalt law that falls under the principle of experience?
figure-ground segmentation
texture gradients
The density of a texture (gradient) provides information about distance
according to texture gradients, where are close vs. far objects placed
Near objects are farther apart and far objects are close together
what principle did they use when building the Magic Kingdom?
texture gradients; the bricks at the top of the castle are smaller to make the castle appear taller
topological breakages
Discontinuity created by the interaction of two textures. Provides information about edges of objects and aids in object identification
pattern recognition theories
emphasize identifying a pattern in visual input
and matching the pattern in visual input to existing patterns stored in memory.
The highest similarity between the probe and memory trace will determine recognition
template matching theory
Every object has a template in long-term memory
criticisms of template matching theory
-too simplistic
-computationally demanding
-can’t explain identification
-can’t explain classification
prototype
the average representation of an object concept
prototype theory
Recognition is determined by a ‘good enough’ match
feature detection theory
Visual input is broken down into individual parts (features). Each feature is processed separately. The combination of features is used as a pattern for recognition to compare to a prototype
geons
basic geometric shapes
recognition by components theory
All objects are reducible to a set of geons. Recognition involves mentally separating a visual object into geons, examining the arrangement, and finding the best match of arrangement to memory representation of geon combinations
scene in consistency effect
an object is named more accurately in a place you would expect it to be than one you wouldn’t
inconsistent scenes and EEG study
An inconsistent scene elicited a negative potential in an N400 response in an EEG, signalling a semantic violation
what kind of processing does direct perception involve?
passive bottom-up approach
interpreting shadows
We use light to interpret shading and shadows, which lead us to see something as protruding or an imprint
why is the auditory system so complex?
Sound waves pass through so many structures to amplify the sound so that the original frequency is maintained in the cochlea
what is sound?
The rhythmic displacement of air molecules
what are sounds made up of?
one or many sinusoidal waves
function of the ear
amplifies, transduces, and transmits sounds into auditory perception
3 main divisions of the ear
outer, middle, and inner ear
pinna in other species
Looks different in different species because the pinna is adapted to catch sounds most relevant to different species. Some species can move their pinnae
where does transduction begin to occur in the ear?
the eardrum
3 types of ossicles
malleus, incus, stapes
why are the ossicles critical?
Needed to further amplify the sound so that it makes it through the fluid of the cochlea
affrent nerves in the auditory system
go from hair cells to the CNS
effrent nerves in the auditory system
go from the CNS to hair cells
where do auditory nerves project to?
to the primary auditory cortex mostly on the contralateral side
where does the primary auditory cortex have connections to?
Broca’s & Wernicke’s area for speech and the primary motor cortex for coordinating movement with sounds
how is frequency measured?
Hz
what does frequency determine?
pitch (High pitch= high frequency)
what are complex sounds made of?
combinations of simple sound waves
how is amplitude measured?
dB
equal loudness contous
pitch and frequency determine loudness perception
phon
a perceptual unit of loudness that correponds to a particular decibal level
what are the main cues for locating sounds in space?
interaural time difference & intraural level difference
intraural time difference
when a sound is made on one side of your body, it will arrive sooner at that side
interaural level difference
when a sound is made on one side of your body, it will be slightly louder on that side
why are our ears good at detecting sound on the horizontal plane?
it’s where they’re placed
auditory scene analysis
the transformation of sound waves into meaningful auditory units (mental representations of sounds). Is based on Gestalt principles & groups sounds in a similar way to how visual input is organized
auditory grouping
sounds come from the same source
auditory separating
sounds do not come from the same source
sequential integration
process of connecting sounds together in time, which results in distinct auditory streams
temporal proximity
how close sounds are linked in time
fundamental frequency
lowest frequency component
harmonics
multiples of the fundamental frequency
how to obtain a target frequency?
shift the fundamental frequency & harmonics around it
amount of information in information processing
the amount of information given by a message is inversely proportional to the probability that the message will occur
what type of processing is involved with inductive reasoning?
bottom-up
what type of processing is involved with deductive reasoning?
top-down
is detecting cinnamon odorants a sensation or perception?
sensation
where does the information in the visual system cross over to the contralateral side?
at the optic chiasm
