lecture 4 Flashcards
What is the process from sensation to perception
stimulus energy, sensory receptors, neural impulses, brain (perception)
can Perception change
Perception is subjective and can change
what does Pain perception depend on
Pain perception changes depending on what is expected
Pain ratings for the electrical shock were higher in the high-cue (high pain expectancy) trials than the low-cue (low pain expectancy) trials despite the shock being at the same level
what is Synaesthesia
Stimulation of one sense simultaneously produces another sensation in a different modality (senses can mix)
what is Grapheme-color synesthesia
¤ Seeing certain numbers or letters as certain colors (red twos and green 5’s)
¤ May be learned (studies show that it may be because we learn the alphabet with colours
what is our dominant sense/percept
Vision
what is the McGurk Effect
¤ Speech sound /ba/ simultaneously presented with visual speech sound /fa/ heard as /fa/
what is A multisensory illusion
change in auditory perception from visual input
is the mcgurk effect a A multisensory illusion
yes
what does the mcgurk effect demonstrate
¤ The integration of sensory information ¤ The power of visual input
¤ It over-rides audio input!
When we see, is there input into the eye or output from the eye
input into the eye
what is the Extramission belief
When we see, there is a ray that exits the eye onto an object (an output; false)
what is the experiment that proved that most people believe that the extramission is correct
Ask participants: How does vision work?
Tested three ways: 1.Computer graphics 2. Verbal descriptions 3. Verbal Reports
Results: The majority favoured a view of vision that had some variant of extramission belief that was found for all ways of testing
when people had education nohow vision worked, do they still believe in extramission
yep, not all but a good chunk of them
what is the difference between early and late visual processing
¤ Early visual processing
¤ Sensation
¤ Eyes and the optic nerve
¤ Late visual processing
¤ Perception
¤ Visual cortex (Occipital lobe)what are the 4 steps of Early visual processing
- Light waves enter the eye, focused onto the retina
- Photoreceptors in the retina convert light to electrical activity
- The electrical signal is sent to bipolar cells and then to the ganglion cells
- The electrical signal is sent to bipolar cells and then to the ganglion cells
4
what is the retina
A thin layer of tissue at the back of the eye
what are the different photoreceptors
- Light waves enter the eye, focused onto the retina
¤ A thin layer of tissue at the back of the eye - Photoreceptors in the retina convert light to electrical activity
are there the same number of photoreceptors as ganglion cells and other cells in vision
NO
Millions of photoreceptors in each retina converge onto 100 x fewer ganglion cells à optic nerve à brain
Millions of photoreceptors in each retina converge onto 100 x fewer ganglion cells à optic nerve à brain
what does this mean
the message from the eyes to the brain is compressed
You don’t ‘see’ everything that is out there in the world
where are Photoreceptors located
back of the retina (farther from the ‘world’)
where are Ganglion cells located
are at the front of the retina (closer to the ‘world’)
Cones (high light level photoreceptors) are mostly where
in the fovea
what is the fovea
¤ A small area on the the central part of the visual field
¤ Most of our detailed vision in the center of our visual field
where are Rods
mostly outside of the fovea, in the periphery
what are the characteristics of periphery
Peripheral vision is less detailed and better for seeing at night
what is perceptual filling in
peripheral vision not as detailed as the centre but we don’t realize because the eye/brain fills in the image around it with details and it looks fine for us
what do the ganglion cells make up
Ganglion cells make up the optic nerve that take this signal to the brain
what is the optic nerve
¤ Ganglion cells make up the optic nerve that take this signal to the brain
¤ Has to move past the photoreceptor layer, so at this ‘exit location’, there are no photoreceptors
¤ This means there is no way to pick up visual stimuli (light signals) at this point (there is a blindspot here)
why do we not see our blindspot
¤The left and right eyes compensate for blindspots ¤Perceptual filling-in
what is Perceptual filling-in
Later visual processes in the brain provide the missing information by ‘interpolating’ visual information (e.g., colors) from surrounding areas
how does Early to late visual processing work
Happens via the optic nerve
Each eye’s optic nerve transmits
information to where
both hemispheres
what half of the brain sees the left visual field
Left visual field is perceived via the
right hemisphere
what half o the brain sees the right visual field
Right visual field is perceived via left hemisphere
what is Contralaterality
information from the world is transmitted to opposite halves of the brain
what are Visual Association Areas
Interprets and understands visual information; assigns meaning to what we see
what are the Different streams in the visual association areas
ventral
dorsal
what is the ventral stream
¤ What (ventral) pathway
¤ Occipital to temporal lobes ¤ Shape, size, visual details
what is the dorsal stream
¤ Where (dorsal) pathway
¤ Occipital to parietal lobes ¤ Location, space, movement
what do neural imaging studies show us about the dorsal and ventral pathways
Neuroimaging studies: object identification vs spatial location tasks activate the what vs where pathways
do the dorsal and ventral streams integrate
yep– they communicate
do we sense or perceive information directly
We don’t sense or perceive information directly
do we receive ALL visual stimuli
no
Visual stimuli is altered/‘broken apart’ in the processing pipeline
¤ Compression
¤ Functional specialization in the primary visual cortex
what is meant by “Perceiving = Constructing”
pieces of information are integrated back together to be interpreted as a whole (from vision)
what is implicit perception
Perception without ‘consciousness’ or awareness that still affects behaviour
how to Measure implicit perception
¤ Blindsight individuals
¤ Laboratory measures
¤ Subliminal priming & backward masking
what is blindsight
¤ Damage to the primary visual cortex
¤ Patients report no awareness of stimuli in their damaged visual field
¤ They can correctly respond to questions about objects presented in the damaged visual field area if given a forced-choice task
¤ They perceive something without knowing it
whats the experiment used for people with blindsight
Test:Turn a light on or off inthe blinded visual field over a series of trials
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Asked the patient to guess if the light is on or off (forced-choice task)
Result: Patients with blindsight perform above chance for forced choice responding about the presence of light in the blinded area
is there much activity is the brain of blight sight people when perceiving faces and houses
¤ Activity of patient with blindsight perceiving faces and houses
¤ Much less than in controls
is there much activity is the brain of blight sight people when IMAGINING faces and horses
¤ Activity of patient with blindsight
when imagining faces and houses
¤ More extensive and similar to controls
what do the findings about the imagery activity in the brain vs perception activity in the brain of blindsight people mean/lead to
idea that There may be other pathways for visual information to bypass the primary visual cortex to be processes
There may be other pathways for visual information to bypass the primary visual cortex to be processes
¤ but These cases rely on what
people reporting their state of awareness ¤ Accepts that people have access to this information
Some individuals with blindsight report a non-visual feeling that something happened– explain
“[it’s like] waving your hand in front of your eyes when they are closed. You are kind of aware that something happened but you don’t quite see it.”
how to test Implicit perception
Subliminal priming
what is Subliminal priming
Test the effect of stimuli presented without conscious awareness (below threshold of awareness – limen) on a measured behavioral outcome
¤ A change in behaviour indicates priming
what is Backward masking
¤Method to present stimuli without awareness 1.Briefly presenting a stimulus (target)
2. Mask that target with a second stimuli
¤ The mask reduces the visibility of the target
¤ Target information is unavailable to conscious report ¤ The target can still influence processing
3.Measure the effect of target information on subsequent tasks: priming experiments
what was the experiment done with backward masking
Measured the reaction time to name the color patch
o Faster naming when the masked target was congruent with the color patch than incongruent (not same colour as word) with the color patch
o Target was processed even when presented below awareness
can Perception occur without awareness
Perception can occur without awareness
what are Blindsight patients
¤Unable to consciously see visual information from the affected visual field but can still respond to it on forced- choice tasks
what are Priming experiments
Information presented to participants that they are not aware of still affects behavioral performance
Change blindness shows that …
¤Not all of our perceptual environment reaches our awareness
¤There is an interaction between attention and perception
processes
¤Our visual experience is underdetermined by (i.e., less than) what is input to the visual system
how is Perception is an illusion!
¤ Information is lost as it is processed in the visual system ¤ We use shortcuts/assumptions to perceive
¤ This is what makes us susceptible to visual illusions
¤ The illusions we are susceptible to illustrate our heuristics
what are heuristics
assumptions about regularities in the world that we bring to perception
¤ We don’t perceive everything in our environment ¤ E.g., change blindness experiment
¤ This is because why
perception is an active and constructive process ¤ We used quick and dirty estimate of the world
¤ This leads to misinterpretations of the world: Visual illusions
Which cells located in the retina are concentrated in the fovea? A.) Ganglion cells B.) Optic Nerve C.) Rods D.) Cones E.) Both Rods and Cones
D.) Cones
