PSYC 300 Lecture Notes - Lecture 7: Sine Wave, Spatial Frequency, Evoked Potential
17 May 2020
School
Department
Course
Professor
Michael Le
ARC
Psych 300
General Principles
The Eye
● Neonate: eyes are half of the adult length
● At one year of age, the eyes are three quarters the size of an adult eye
Experimental Techniques
● Forced choice preferential looking
● Idea that an infant would rather look at something than nothing
● Acuity - determining how sharp their vision is
● Sine-wave grating
● Two screens: one with the sine wave grating and one with a plain grey field, but
both have the same amount of grey
● Determine acuity through this test by observing how many times the infant looks
at the sine wave grating instead of the grey field
● Must be randomized
● By varying spatial frequency you can determine the level of acuity
● Skinny bars are high frequency and thicker bars are lower frequency
● Habituation
● Children instinctively look at things that are new instead of things that are old
● Works with frequency as well
● If a child is shown a certain frequency, then shown another, if they can determine
a difference, the child will look at it and focus on it
● Surprise
● Children prefer looking at things that surprise them rather than things that are
expected
● If a child is looking at a curtain and shown two toys when the curtain is pulled by
● If you pull the curtain back again after showing the child that you’re putting
another toy there and there are still only two toys and the child looks at it again,
we determine that the child has a concept of numbers and realizes that there
should be another toy there
● Electrophysiology (EEG)
● Can infant see flicker?
● At what speed can the child no longer see the flicker (20Hz, 40Hz)
● For adults, 60Hz (flickers per second) is the point at which we can no longer see
the flicker
● At lights of less that 60Hz, we notice flickering
● With children we flicker the lights on the computer and if the child sees it, the
EEG will show activity of equal hertz in their own brain
● When their brain stops having equal hertz as the light the visual evoked potential
has been reached and the brain cannot keep up
● We can see this in children at two months of age with a flicker fusion of 60Hz
(equivalent to an adult)
● Innate behaviors
Document Summary
Neonate: eyes are half of the adult length. At one year of age, the eyes are three quarters the size of an adult eye. Idea that an infant would rather look at something than nothing. Acuity - determining how sharp their vision is. Two screens: one with the sine wave grating and one with a plain grey field, but both have the same amount of grey. Determine acuity through this test by observing how many times the infant looks at the sine wave grating instead of the grey field. By varying spatial frequency you can determine the level of acuity. Skinny bars are high frequency and thicker bars are lower frequency. Children instinctively look at things that are new instead of things that are old. If a child is shown a certain frequency, then shown another, if they can determine a difference, the child will look at it and focus on it.
