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Lecture 9

PSYC 2390 Lecture Notes - Lecture 9: Earwax, Sound, Motion Perception

Course Code
PSYC 2390
Lana Trick

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November 30, 2016
Olfaction pg368-378
Final Exam:
-December 9, 230-420
-Chapter 10 231-end
-Chapter 5,8,11,15
-Lectures nov 9 and on
-30 multiple choice and two essay questions
-Textbook questions
-Essay questions: one part is on theories of pitch perception
Motion Perception
-The ability to see movement and change
-Bunnies can not get depth perception because their eyes face outwards
Motion Defines Object Form & Can Aid in Object Perception
-Motion can help you find form
1. Grouping by Common Fate
-Example: when she had a dotted figure overtop of dotted background and when it
moved we could see the object but when it was still we could not
-This is grouping in 2D
2. Biological Motion: Johansson Figures
-All black figure with lights at their joints
-We can look at the way things move and we will be able to figure out what it is
-We can tell biological motion but we can also tell which species it is
-Males from females, sad from happy with body language
Motion & Visual Motor Coordination
1. Motion and Balance
-Optic Flow
-Needing to use our eyes to be able to determine where vertical is
-Standing on one leg and closing your eyes experiment in class
-Swinging Room Experiment
-They took a toddler in a room and the walls are hanging down from chains so
they can move them back and forth
-If the walls are flowing towards you, you feel like you are falling forwards and
you lean backwards
-This experiment links optic flow and posture
-You pay more attention to your vision than your inner ear on the perception of
this experiment
Real vs. Apparent Motion
-Apparent Motion:
-Frame 1 has a dot in the bottom left and frame 2 has a dot in the top right, if you
used a flip book it would look as if the dot went diagonal
-Werthei/Exner: if you had less than 30ms you would not see the motion, 60-200
ms you would be able to, if the time between the first frame and second is too
long, you will see static pictures
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November 30, 2016
Two Systems of Motion Perception
1. Image Retina System
-Relies on the fact that things have certain spots on the retina
-Example: you are looking at a waterfall for along time, if you turn away things seem to
be going upwards (only works if you keep your eyes still)
-Spiral After Effect: the part of the spiral moving inwards created your friends face to go
outwards and vice versa
2. Eye Head System
-Used to track objects
-Based on the fact that if you are looking at something like a golfball moving across the
floor you can still track it with your eyes and head movements
Difference Between The Two
-Aubert-Fleischl Effect
-Both systems will tell us the object is moving but each will give different speed
-If something is moving faster than your eyes can move, your eyes underestimate how
fast it is moving
Neural Processing of Motion
-Magno Retinal Ganglion
-Magno cell: (large with thick axon) sends info rapidly, cant see colour or pattern but
sensitive to change, we have more in cells in the periphery vision than in the centre
which created higher sensitivity in the periphery
-Superior Colliculus: (eye head system)
-Striate Cortex: complex cells respond to motion, hypercomplex respond to width
-Effects of early deprivation: kitty experiment
-Cats are blind as babies and develop their eye sight
-If you raise the cat in the presence of a strobe light it will develop stroboscopic
-Motion sensitive cells in the striate cortex wont develop
-Medial Temporal Cortex
-Cerebral Akinetopsia: seeing the world in frozen moments
Problems in Motion Perception
-Difficult to recognize movement in the real world or our own movement
-Example: Induced Self Motion Illusion: if you are sitting and then a train starts to move, you
think you are moving (if it is covering your entire visual field)
-Driving Stimulator: the optic flow (moving) and the inner ear (vestibular system) is still
-It is highly likely for woman and especially older women will make them sick (video
games too)
-Corollary Discharge Theory: READ TEXT (exam question)
-How do we know whether it is the eyes that move or the world that moves???
-Motor cortex sends signal to eye to move
-According to this theory: when you make an eye move you send a copy (or corollary)
from the eye to the comparator of the motor signal
-Image Retina Signal (Sensory) from eye to comparator
-If you have your eyes still, and things shift on your retina (sensory signal) then you will
have real life motion!
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November 30, 2016
-If you are moving your eyes and everything is staying stationary, both are in
corresponding movements or stationary
-Experiment: Gun experiment: you get paralyzed and you can not move your eyes, the
intention from the motor cortex is enough to see things move but you did not actually
-Humans underestimate the speed of large objects
Audition (Chapter 11)
Stimulus for Hearing: Sound
-Sound: mechanical energy (when molecules push up against each other)
-It is practically a pressure wave
-When you hear something it is a chain reaction
-If you are in space, no one can hear you because there is no molecules
-High atmospheric pressure is compression
-Low atmospheric pressure is rarefaction
Properties of a Sound Wave
1. Amplitude
-The distance between the x axis and the top of the wave
-Loudness is how sound pressure levels (force/unit area)
-Softness sound we can hear is 0.0002 dynes/cm2
-Decibel (Db): 20 x log (actual sound pressure/0.0002dynes/cm2) (P/Po)
-10^0 is the threshold of hearing, as it increases by 10 sound increases
-10^7 is when the danger level begins
-10^8 is annoying
-After 10^1o prolonged can cause hearing loss
-10^14 is threshold of pain
2. Frequency
-If you were standing beside a swimming pool, and you dropped a rock, you could
count how many waves hit the edge of the pool per unit time
-Measured in Hertz (Hz)
-Different Species perceive different frequencies
-Cats,dogs and bats can hear higher frequencies
-Elephants can hear low frequencies allow them to hear when storms are coming
3. Timbre
-Quality of the sound
-Closest sound to a sin wave is a flute
-Complex wave forms are what we hear
-Fourier Theorem: complex wave is sum of 4 sine waves of different frequencies and
amplitudes and phase angles
-Example: the same instrument can play the same note but sound different because
they have different frequencies (Each instruments timbre is the quality of each
instruments note)
4. Phase
-Phase Angle: what position are you at in the sine wave? (0 degree, 90 degree, 180
degree or 360 degree)
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