PRINCIPLES OF PERCEPTUAL MEASUREMENT
A. Scientific basis of perceptual measurement
What do we gain by taking a scientific approach to perception?
- Satisfies intellectual curiosity
- First step to understand perception is to establish a quantifi
Hermann grid illusion:
While looking at these Hermann grids one gets the fleeting impression of a set of spots
at each of the intersections.
Interestingly, a spot disappears from an intersection if the eyes are shifted directly to it.
The Hermann grid
1. Scotopic versus Photopic Vision:
4 key points to keep in mind when comparing scotopic and photopic visual function:
1 scotopic vision is extremely sensitive and therefore operates only
under dim light; photopic is less sensitive.
2 although there is
Measures of spatial resolution contrast sensitivity function:
The major drawback of the Snellen chart = provides only a rough assessment of visual
acuity because the letters are all made of the high contrast characters, whereas vision
normally operates o
Integration over space and time:
Riccos law = states that the product of light intensity and stimulation area (total amount
of light) must reach a critical level for detection to occur.
o Less intensity is needed if more area is stimulated.
Retinal wiring differs with eccentricity:
In the fovea only, a single photoreceptor is connected to a single bipolar cell that is in
turn connected to a single ganglion cell = spatial sampling = one light detector is
ultimately attached to one output neu
o When the light spot is made large
cover the entire receptive field,
ganglion cell will theoretically fire
spontaneous rate because the
through its center is
counterbalanced by the inhibition
It is this
Absorption spectrum of cone rhodopsins:
The retina contains more than one type of cone photoreceptor.
o This made it hard to proceed with the same experiment used for the rod
Microspectrophotometry = procedure of spectrophotometry to be minia
A. Optical Disorders of the Eye
The process of accommodation depends on the elastic quality of the lens, which allows
it to assume a more spherical shape for viewing closer objects when greater refractive
power is needed.
With increasing ag
Chapter 8 (lecture 15 + 16): The Visual System: Light, Optics, and the Eye
Vision allows sensory perception to occur for the greatest distance because it uses light
as the carrier of information.
The importance of vision in evolutionary te
1. The Lateral Geniculate Nucleus:
The LGN is a 6-layered neural structure that serves as the main projection target of the
Structural and functional properties of the LGN:
LGN receives approximately 90% of the retinal fibres contained in th