Sensation & Perception Part B Flashcards
How do we perceive depth?
by using different cues, divided into 3 groups:
oculomotor cues
monocular cues
binocular cues
example of binocular disparity
If you hold your finger out at arm’s length and then look at it alternately with your left eye only and then your right eye only, the image of your finger relative to the world behind it will shift somewhat. This is binocular disparity, which helps provide the basis for the determination of depth.
RELATIVE DISPARITY DOES NOT CHANGE BUT ABSOLUTE DISPARITY DOES
What is the correspondence image?
- retinal images can be ambiguous
- if there are multiple identical objects in the scene it can be hard to figure out which images in the left retinal image should be associated with which images in the right retinal image
how can the correspondence problem be resolved?
if the objects in the visual scene are made distinct from one another by colour e.g. the associations become unambiguous
what is the horopter?
the plane containing all points that will fall on corresponding parts of the 2 retinas
size constancy equation
S= K x (R x D)
S = apparent size of object
K is constant
R = size of retinal image
D = perceived distance to object
Size illusions - how do they work?
if an object appears closer than it really is, it will appear SMALLER than it really is and vice versa
e.g. Ames Room
Holway & Boring (1941)
- investigated how observers estimate size of objects –> how DEPTH cues influence size judgments
- observer sat at intersection of 2 corridors & could view a test circle in 1 corridor & comparison circle in another corridor
- their task was to adjust the size of the comparison circle to match the size of the test circle
- test circles were of dif sizes by were presented at dif. distances so that their angular size was always the same
REVIEW HOLWAY & BORING (1941)
condition 1: observers could determine the depth of the test patch using binocular disparity, motion parallax, & shadows
condition 2: observes viewed the test circle with one eye to remove binocular disparity cues
condition 3: observers viewed the test circle through a peephole to remove motion parallax cues
condition 4: in addition viewing the circle through a peephole, drapes were used to remove shadows
How are depth & size related?
how big an object appears can affect how far away it appears & how far away an object appears can affect how big it appears
how can the correspondence problem be resolved?
if the objects in the visual scene are made distinct from one another by colour e.g. the associations become unambiguous
What determines the perceived size of an object?
its angular size
its perceived depth
angular size
the visual angle an object subtends
the closer an object is to person, the larger its angular size
what is size constancy?
the phenomenon where an object’s apparent size does not depend on its physical distance
When an object is far away it appears to
be the same size as when is it closer…
…even though its visual angle is much
larger in the latter case
how to achieve size constancy?
consider both the size of the retinal image AND the distance of the object
if someone misestimates the distance of an object. . .
they will probably misestimate the SIZE of the object
What did holway & boring (1941) conclude?
- concluded that when there are sufficient depth cues, the size of the test patch can be accurately estimated
- when there are not sufficient depth cues, the apparent size of the test patch is BIASED towards the VISUAL ANGLE
further away test patches are PERCEIVED AS SMALLER THAN THEY REALLY ARE
Accurate size estimates can occur only
when distance to the object can be
estimated accurately
Ames room illusion
When a person moves to the left-hand side of the room, they are actually further away and the ceiling is higher. They appear as a smaller image on your retina and you therefore perceive them as small. The opposite effect occurs on the right-hand side of the room
physical definition of sound
sound is PRESSURE CHANGES in the air or other medium (e.g. sound waves in water)
perceptual definition of sound
sound is the EXPERIENCE (i.e. sensation) we have when we hear
pressure waves (sound waves) move through air & water at. . .
air: 340 m/s
water: 1,500 m/s
each air molecule is just moving back & forth to create regions of high + low pressure
when does a PURE tone occur?
occurs when the change in air pressure occurs in a pattern described by a mathematical function called a sine wave (w/ amplitude)
time on x axis, air pressure on y axis
the higher the frequency, the ___ the pitch
higher