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Chapter 3

PSY270H5 Chapter Notes - Chapter 3: Parietal Lobe, Prosopagnosia, Fusiform Gyrus

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Christine Burton

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Notes From Reading
Visual Sensation and Perception
Light waves enter the eye, are focused and inverted by the lens, and are projected onto the retina
The retina have three layers of neurons: rods and cones, bipolar cells, and ganglion cells
oThe rods and cones are neurons stimulated by light, beginning the process of vision
oPatterns of neural firing from these are passed on to a second layer, the bipolar cells,
which collect the messages and move them along to a third layer, the ganglion cells
oThe axons of the ganglion cells converge at the rear of the eye, forming the bundle of
fibers that makes up the optic nerve
oThe signal exits the eye ad continues through various structures, eventually projecting to
the visual cortex of the occipital lobe, in the lower rear portion of the brain
Each eye transmit information to both hemispheres
Each half of the retina gathers information from the contralateral visual field
Where you are looking is your fixation point
The left half of the retina in each eye receives images from the right visual field and is sent to the
left hemisphere, and the right half of each retina receives images from he left visual field and is
sent to the right hemisphere
The message that finally reaches the cortex is an already processed and summarized record of the
original stimulus
There are about 120 million rods on each retina and about 7 million cones
Most of the cones are in the Fovea: Which provides our most accurate, precise vision
In peripheral vision, tens to hundreds of rods converge on a single bipolar cell, resulting in a loss
of information because a bipolar cell cannot “know” which of its many rods triggered it
About 1 million ganglion cells combine to form the optic nerve
The messages reaching the brain have been reduced and summarized to an enormous degree
Sensory and perceptual processes influence cognition even based on general visual properties or
impressions of a scene as a whole
Sensation: The reception of stimulation from the environment and the encoding of it into the
nervous system
Perception: The process of interpreting and understanding sensory information
Gathering Visual Information
Vision is triggered when the reflection of light from an object hits our eyes
Saccades: Eyes sweep from one point to another in fast movements
Fixations: Eye movements that are interrupted by pauses (jerk movements)
Change Blindness: Failure to notice changes in visual stimuli (i.e., photographs) when those
changes occur during a saccade
Attention must be interruptible: we need to be able to react quickly to the unexpected, as when
sudden movement alerts us to a possibly dangerous situation
Visual attention should not be too interruptible: we cannot constantly be switching from one thing
to another
Inattention Blindness: We sometimes fail to see an object we are looking at directly because
attention is directed elsewhere
Visual Sensory Memory
Visual Persistence: The apparent persistence of a visual stimulus beyond its physical duration
Iconic Memory/ Visual Sensory Memory: A temporary visual buffer that holds visual
information for brief periods of time
Amount and Duration of Storage

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Notes From Reading
Sperling and coworkers presented a visual stimulus for a controlled period of time, usually on the
order of milliseconds, to study the information available in brief visual presentations
A typical iconic memory experiment presented arrays of letters and digits to people for brief
durations. The task was to report what could be remembered from the display. Sperling found that
on average 4.5 items were recited correctly.
Span of Apprehension: The number of items recallable after any short display (a.k.a. span of
attention or span of immediate memory)
Whole Report Condition: People are to report any letters they can
Partial Report Condition: Only one of the rows was to be reported
Sperling created a partial report condition and the participants didn’t know this
He had a high tone, sounded right after the display went off, was a cue for reporting the top row, a
medium tone for the middle row, and a low tone for the bottom row
When the tone followed the display immediately, performance was 76% correct suggesting that
visual memory of the entire display must also be 76%
This suggests that immediately after seeing a visual display, a great deal of information is
available in visual sensory memory, much more than can be reported aloud
Icon: The visual image that resides in iconic memory
Decay: A passive process like fading
Interference: Forgetting caused by the effects of intervening stimulation or mental processing
In another study by Averbach and Coriell, presented a display of two rows of letters, eight letters
per row, for 50 ms. They used a visual cue, either a vertical bar marker or a circle marker.
Backward Masking: A later visual stimulus, if it occurs soon enough after the display, interferes
with the perception of the earlier image at the same spot
The Early Parts of a Fixation
As you read these words on this page, you are not viewing them continuously
You are seeing them in brief bursts, extracting information quickly and then devoting mental
energy to processing them further, unaware of your “down time” during the fixation and of your
blindness during the following saccade
“Dynamic icons” are iconic image that contain movement
Visual perception is a process of focusing on the visually attended elements of successive
fixations, where each fixation encodes a dynamic segment of the visual environment
Integration across brief intervals of time can occur even without eye movement
A Summary for Visual Sensory Memory
Focal Attention: Mental process of visual attention
It seems that focal attention, or simply visual attention, helps bridge between successive scenes in
visual sensory memory
Although we sense a great deal of visual information, what we perceive is the part of the visual
scene selected for focal, visual attention
Trans-saccadic Memory
Trans-Saccadic Memory: The memory that is used across a series of eye movement
Trans-saccadic memory works by using what are called object files, which are iconic
representations of individual objected used to track what is going in the world
Pattern Recognition
During perception a person needs to identify the nature of the distal objects in the world based on
the proximal images reaching the retina
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