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PSY100H1 Lecture Notes - Eardrum, Gestalt Psychology, Cochlea

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Michael Inzlicht

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I. Auditory Perception
Sound waves --> peaks and lowest points are amplitude, which
determines our perception of loudness and frequency determines our
perception of pitch.
Ear Anatomy --> sound waves go into the ear canal, vibrate the ear
drum, causing the bones (ossicles) to move back and forth. Their
movement vibrate the cochlea. Di!erent parts along the cochlea
corresponf to di!erent frequencies. Between the ears and the brain,
sound processing occurs along the auditory pathways --> involves
comparing the signals from both ears and analyzing them (intensity,
where it came from). Sound entering the left ear is processed by the right
side of the brain and one entering the right ear is processes by the left
Dorsel "where" stream --> pathway that process spatial info.
Ventral "what" stream --> determines identication
Primary auditory cortex --> 1st place in the cortex
How does the auditory system seperate di!erent sounds from one
Sound segregation --> we must be able to seperate the sounds --> we
must be able to group or integrate sounds over times (known as
sequential sound segregation)
Concurrent sound segregation --> 3 di!erent sounds added together to
lead to a summed wave --> This summed wave goes into our ear and
how does the brain seperate them? Auditory System processing receives
the summed wave and then seperates them.
Grouping principle in audition: Gestalt grouping principle --> if 2 sounds
come from a common location, have common frequencies and have
common onset, they group together and perceive as one sound.
Grouping by freqyency --> As higher freuqncies are added by the
intervals of 200Hz, the sound gets "deeper" and "louder" --> every single
sound can be broken down into frequency components --> even though
11 tones are being added, at the highest freuquency, we only hear one
sound, not all 11 at the same time.
Mistuning one harmonic, meaning increasing that frequency by 8Hz (4%
in total), then increased to 8%, there is a seperate tone present, so it is
starting to split into 2 di!erent sounds --> sounds are segregating.
How we group frequencies over time --> A and B tones are put together:
(1) B tone is" a bit higher in frequency than the A tone and this is called
gallop perception

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(2) As the B frequency di!erence from A is increased a lot more, the
sound splits into 2 streams and this is called streaming --> we hear 2
sounds of low and high frequency stream
(3) Bi-stable perception: sometimes gallop and sometimes streaming -->
can study what the brain is doing when it is streaming or when they are
put together --> Stimulus are the same, same physical inputs, but 2
di!erent perceptions
Real-Life Application --> how we are able to di!erentiate between
sounds in a crowded place --> sounds have to be seperated and this is
called concurrent sound segregation and maintain the seperation over
time in order to understand the sound that one wants to listen to.
Perception of sound relies on Gestalt grouping principles. We must
seperate di!erent sounds that occur concurrently and keep them
seperated over time in order to communicate e!ectively.
II. Sensation and Perception
"The real problem is not whether machines think but whether men do.
The mystery which surrounds a thinking machine already surrounds a
thinking man --> experience teaches our brains how to perceive reality,
giving us knowledge about what the world looks like. We then use this
knowledge to guids the process of contructing perceptions. When we are
pereiving, we have 2 streams of processes going on (top-down stream is
pre-existance knowledge that have developed over time, what nature has
already taught us) (bottom-up: world informing the brain at the moment
of perception: information coming in at that instance) both processes
combine and top-down interpret bottom-up and turn it into meaningful
seperation. The process go through di!erent directions o neurons that
exist in our brain --> smashing together of top-down and bottom-up.
Sensations refers to how sense organs respond to and detect external
stimulus energy, and how those responses are transmitted to the brain
bottom-up: how our sense organs respond to the energy of the brain
process of how we turn the sitmulus energy of the world into an internal
sensation + perception: 6 steps from sensation to perception
the world -- reality occurs
observer enters and their receptors come into contact with the reality
transduction --> light energy goes through the photo-chemical reaction,
which produces cells --> visual information is compressed
(interpretation) and then compressed further into (neuro-signals) axons
and is then sent to the brain
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