H7 Psychology of vision Flashcards
What is the function of the cornea and adjustable lens?
And function of iris?
Focus incoming light onto the retina at the back of the eye’s interior. Iris increases or decreases diameter of pupil.
How does transduction of light energy take place?
2 types of photoreceptors in retina (rods and cones) contain photochemicals (rhodopsin for rods; 3 varieties of cones each containing a different photochemical) that react to light with structural changes. This leads to further chemical and electrical changes that trigger action potentials in neurons that form the optic nerve
What is the function of rods vs cones?
What is the chemical basies for dark en light adaptation?
How are they concentrated on the retina?
Cones: color vision, high visual acuity and ability to see bright illumination
Rods: sensitivity that allow vision in dim illumination
We see only with cones in bright light and only with rods in dim light.
Rhodopsin becomes inactive in bright light
Cones are concentrated on the fovea and concentration decreases moving away from it.
Rods are not present in fovea. Highest concentration in ring 20 degrees from fovea.
Wat is the blind spot?
Place on retina where optic nerve connects; no rods or cones there.
How do we experience different colors?
Objects reflect different wavelengths of light. Pigments of objects absorb some wavelengths from white light and reflect othes.
What do the three-primaries law and law of complementarity say when it comes to color mixing?
Three-primaries: 3 different wavelenghts of light can be used to match any colo that the eye can see if they are mixed in the appropriate proportions. Can be any 3 wavelenghts, as long as you take one from each of the 3 parts of spectrum: 400 nm blue > green > red 700 nm.
Complementarity: some pairs of wavelengths when combined produce visual sensation of white.
What is the opponent-process theory of color vision?
How do you explain complementarity of afterimages?
Physiological units involved in color vision are affected in opposite ways (excited or inhibited) by complementary wavelengths:
There are 3 sets of neurons:
1. blue-yellow opponent: if one is excited the other is inhibited
2. Green-red opponent: if one is excited the other is inhibited
3. Ability to distinguish bright light from dim ligth, independent of wavelenght.
. It explains the law of complementarity in color mixing and the complementarity of afterimages (neurons become fatigued and opposite neurons take over).
Why does vision in some people obey a 2-primaries law rather than the 3-primaries law?
how does color vision of most nonprimate mammals and that of most birds differ from that of most humans?
1 cone is missing, usually green or red due to defect gene. So can’t distinguish colors on long end of spectrum.
Same goes for most nonprimate animals. Birds have a 4th cone to detect light below 400 nm.
How has the opponent-process theory been validated in studies of the activity of neurons that receive input from cones?
Ganglion cells (neurons of optic nerve) translate trichromatic code of cones into opponent-process code.
How has the opponent-process theory been validated in studies of the activity of neurons that receive input from cones?
Ganglion cells (neurons of optic nerve) translate trichromatic code of cones into opponent-process code.
What are experience-expectant processes and how do they relate to the development of vision?
Process whereby synapses are formed and maintained when an organism has species-typical expeiences.
If species-typical environment is absent, animal may not develop normal vision.
In what sequence are visual features processed?
Treisman’s feature integegration theory of perception.
Detected through rapid parallel processing and integrated spatially through serial processing.
What does the gestalt psychology say about vision?
What do the gestalt principles say
Objects are not the sums of parts and wholes take precedence in conscious perception.
The gestalt principles of grouping describe rules by which we automatically organize stimulus elements into wholes. We also automatically separate figure (object that attracts attention) from ground (background).
How is our perception of wholes influenced by perception of parts? By what is this illustrated?
It is top-down or bottom up?
By unconscious interference: phenomena in question result from neural activity in higher brain areas. Illusory contours and illusory lightness differences.
Top down processing.
What are visual form agnosia and visual object agnosia?
Is the what or where pathway damaged?
Form: see something is present and describe some of its features but cannot perceive shape
Object: can describe and draw shape but cannot identify object
Both due to damage to what pathway.
