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Perception, 4/e

Robert Sekuler, Brandeis University
Randolph Blake, Vanderbilt University

The Eye and Seeing


1	Action potentials are
		A)	brief electrical discharges carried by nerve fibers.
		B)	the method by which information is carried across a synapse.
		C)	initiated by the photoreceptor after transduction.
		D)	all of the above.


2	Which statement about retinal ganglion cells is false?
		A)	There are far fewer ganglion cells than photoreceptors.
		B)	They only initiate action potentials when stimulated.
		C)	They can generate both ON and OFF responses.
		D)	Their axons comprise the optic nerve.


3	Receptive fields are defined as the
		A)	spatial range over which an individual can see at a given time.
		B)	spatial range over which light increases the response of a cell.
		C)	spatial range over which light has an influence on a cell's response.
		D)	concentric center/surround layout of retinal ganglion cells.


4	One of the most important effects of lateral inhibition is that it enables cells to
		A)	emphasize absolute intensity levels.
		B)	produce OFF responses.
		C)	reduce their spontaneous activities.
		D)	emphasize light and dark boundaries.


5	With increasing eccentricity, the size of receptive fields tends to
		A)	increase
		B)	decrease.
		C)	stay the same.
		D)	be widely variable.


6	At a given retinal eccentricity, the size of P ganglion cell receptive fields tends to be
		A)	larger than M cell receptive fields.
		B)	smaller than M cell receptive fields.
		C)	the same size as M cell receptive fields.
		D)	unrelated to M cell receptive fields.


7	Which of these is not a difference between P and M ganglion cells?
		A)	conduction velocity
		B)	population percentage
		C)	contrast sensitivity
		D)	presence in the fovea


8	Center surround receptive fields have been used to help explain which of these illusions?
		A)	Mach bands
		B)	Zollner arrows
		C)	Ponzo illusion
		D)	Ebbinghaus circles


9	One limitation of the explanation of lightness constancy based on center surround receptive fields in the retina is perceived lightness can be affected by
		A)	perceived depth
		B)	overall illumination
		C)	perceived spatial curvature
		D)	neighboring physical intensity


10	With increasing receptor convergence you get _______ resolution and ________ sensitivity.
		A)	increasing; increasing
		B)	increasing; decreasing
		C)	decreasing; increasing
		D)	decreasing; decreasing


11	Bloch's Law states
		A)	a constant product of light intensity and time will be equally detectable.
		B)	a constant product of light intensity and area will be equally detectable.
		C)	detectability is determined only by the light intensity.
		D)	detectability is determined by the product of light intensity and wavelength.


12	As light intensity drops to __________ levels, vision is dominated by _________ photoreceptors
		A)	photopic; cones
		B)	photopic; rods
		C)	scotopic; cones
		D)	scotopic; rods


13	The phenomenon where the perceived lightness of objects of different wavelength depend on the time of day is called
		A)	the Purkinje shift.
		B)	the Abney effect.
		C)	the Helmholtz shift.
		D)	Ricco's law.


14	In order to apply Abney's Law we need to know
		A)	the sensitivity of the visual system as a function of wavelength.
		B)	the intensity of the light at a given wavelength.
		C)	the wavelengths present in the stimulus.
		D)	all of the above.


15	A bend in the dark adaptation curve indicates
		A)	a malfunctioning visual system.
		B)	sensitivity is mediated by either the rods or the cones, depending on which is more sensitive at the time.
		C)	improvements in sensitivity occur first due to pupil dilation, then due to neural factors.
		D)	a botched experimental design.

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