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Midterm

PSYC 3702 Study Guide - Midterm Guide: Retina, Fusiform Face Area, Temporal Lobe


Department
Psychology
Course Code
PSYC 3702
Professor
Brian Tansley
Study Guide
Midterm

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1. Describe the psychophysical law most often associated with 'absolute and differential
threshold' measurements and describe a real-world example where differential threshold
determinations are made (PAGE 21)
Webers Law. This is the fraction that shows the systematic relationship between the size
of the Just Noticeable Difference (JND) and the Standard Stimulus
absolute: can you detect the stimulus?
oMethod of Adjustment
oMethod of constant stimuli
oStaircase method
oMethod of limits
differential: difference between 2 stimuli
oLooking up at the sky and directing our eyes towards the blue rather than the
Sun (the Sun is too bright to look at directly)
2. Compare and contrast binocular and monocular depth cues (PAGE 193-195)
binocular: depends on both eyes together ei - difference in the relative position to
perceive depth(Retinal Disparity and Convergence)
monocular: Static (position, size and lighting) and Dynamic (optic flow, motion parallax,
deletion and accretion) Available to either eye alone
3. What is the Principle of Univariance and how does it help explain some of the colour
vision phenomena we observe? (PAGE 163,165)
Cones: respond to differences in light intensity more than differences in wavelength
Rods: respond to differences in wavelength more than differences in light intensity
Different colours are experienced as different shades of grey at night when vision is
mostly with rods
The absorption of a long wavelength (low frequency, low energy) quantum has the same
effect on a receptor as the absorption of a short wavelength (high frequency, high
energy) quantum. It is the probability of absorption that changes photoreceptor
sensitivity.
4. Describe the RBC (Recognition by Components) Theory of Object Recognition and
briefly discuss its strengths and weaknesses (page 121)
Recognition by Components Model : “objects are recognized by identities
and relationships of their component parts.”
Strengths: Object recognition by components then allows us to identify
many common shapes that make up an object. And identify an object in middle
vision quickly (after first stimulus but before higher order concepts).
Weaknesses: However this element of visual perception is highly
dependent on view point. So component shapes are not always recognized from
each angle. This theory then presents an incomplete way to understand how we
recognize objects.
5. Describe the zone theory of colour vision. (page 171)
Zone 1: Transduction. S, M, and L cones differentially transduce photons of different
wavelengths
Zone 2: Opponent mechanisms code for differences between opponent primaries
oq[L – M] and [M – L] compute red vs. green
oq[L + M] – S and S – [L + M] compute blue vs. yellow
Zone 3: Appearance. Further recombination of the signals creates final color-
opponent appearance that has ‘top-down influences from memory
6. Compare and contrast 'efficient' and 'inefficient' visual search tasks.
Visual Search: Searching for one specific target in a scene containing objects.

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Feature Search: search an array of items for something that is different in just one
feature.
oEffective - if there is only one main distinguishing element from the rest. An
example would be looking
ofor the only yellow car in a parking lot.
Conjunction Search: searching a display for an item differs from all other items in the
display by having a particular combination of two or more features.
oIneffective - looks for several different elements that combine to make a distinct
object, therefore its slower because more information must be processed. This
includes the binding problem where several features must be grouped together in
order for the brain to recognize a whole object. An example would be looking for
a yellow convertible in a parking lot with several other yellow cars and
convertibles.
7. Compare and contrast the ventral and dorsal 'streams' of the post V1 visual pathway.
(P.105).
Ventral: from V1 and V2  V4  inferotemporal cortex. Represents properties of an
objects identity (colour and shape) The “what” pathway.
Dorsal: passes from V1 and V2 MT parietal cortex. Represents properties of an
objects motion (also guides action) The“where” and “how” pathway.
8. Distinguish 'colour memory' from 'memory colour'
Colour memory  ability to ‘hold’ the perception of a specific colour or set of colours in
short term memory (a critical perceptual capacity for certain skilled trades  porcelain
painting
Memory colour  refFlects the categorical nature of remembered perceptual
experiences (remembered colours tend to be more saturated than the original stimulus 
important information for production and marketing purposes)
9. Compare and contrast, with examples, additive and subtractive colour mixture.
Additive Colour mixture: a mixture of different coloured lights  perceived colour of the
mixture is the result of adding together all the wavelengths of light in the mixture
oExample = adding light filters to create new hues on a stage.
Subtractive Colour mixture: called subtractive mixture because certain wavelengths
are not reflected but absorbed by substances in the mixture.
oExample = mixing paint to produce a new colour.
A white sheet of paper reflects all colours equally, so the colour we see depends only on
the mixing of wavelengths, (red and blue will make purple). A brown paper may absorb
(subtract) certain wavelengths and not reflect all colours equally. This means the colour
we see reflecting off brown paper will be different from the colour of a purely additive
colour mixture on a white piece of paper.
10. Describe any 5 monocular cues to depth and provide real-world examples where each
may be observed (2 points each) (Pg 195)
Partial Occlusion: a position based depth cue. Where one object partially covers
another, the former is closer than the latter.
osA woman may stand in front of a taxi, and therefore since she is
‘occluding’ the taxi, she is closer.
Relative Height: a size based depth cue. An objects position relative to the
horizon provides information about distance. An object that appears to be smaller will be
further away.
oTrees closer to the horizon will appear smaller than those closer to you.

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Texture Gradients: a size based depth cue. Variations in the texture of an object
indicate its position. Objects with more visible detail are closer.
oRocks on a beach: rocks further away will blend together and details will
be indistinguishable, rocks closer to the viewer will have more detail.
Linear Perspective: A size based-depth cue. Parallel lines will converge as they
get further away.
oTrain tracks will appear as though they are coming to a point as they
recede into the distance.
Atmospheric Perspective: A lighting based depth cue. The farther away an object,
the more air the light has to pass through to reach the eye. Objects that are further away
appear to be blue (atmosphere tends to scatter short wavelength light more than others).
oMountains in the distance will appear to be blueish or grey compared to
ones closer to the viewer.
11. A significant proportion of the population is 'stereoblind' – that is, does not have
stereopsis. For the most afflicted, this is a preventable condition. Describe the main
cause of stereoblindness and outline how stereoblindness is prevented.
Stereoblindness occurs when both a person’s eyes do not point in the same direction 
Causes the brain to only process information from one eye at a time to reconcile the
image.
Cause = eyes not being aligned at birth or throughout childhood. Cured through
exercises that train the eyes to focus on a single point or with eye patches
12. “Deuteranopia” is the most common form of dichromatic vision. Explain its cause, its
incidence and describe how it is diagnosed.
Deuteranopia lack one type of cone function (medium) = wavelengths for green light
Typically passed down through genes  mothers are often carriers, but girls will only be
colour blind if they inherit the trait from both parents. (Boys only have 1 X chromosome
that needs to be affected, girls have 2)
Also caused by traumatic injury or through disease. Diagnosed with pseudoisochromatic
plates
13. Define the term “colour constancy” and describe the problem that it solves for
consciousness.
The tendency of a surface to appear the same color under a fairly wide range of
illuminants
Must determine what the true color of a surface is regardless of how it appears  Helps
us identify objects
14. Compare and contrast the “canonical view” of an object with other views of the same
object. What implications do the existence of canonical views of objects have for object
recognition?
View at which the object is most easily recognized  beneficial for life in the wild - easily
recognize food, predators and shelter
15. Explain the term middle vision and provide examples of the kinds of processes
associated with it.
A loosely defined stage of visual processing that comes after basic features have been
extracted from the image and before object recognition and scene understanding takes
place
Involves the perception of edges and surfaces + Determines which regions of an image
should be grouped together into objects
16. Human visual perception is characterized by, among other things, “figure-ground
segregation” that is, rapid, effortless assignment of scene elements into either a figure or
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