Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
54 Cards in this Set
- Front
- Back
|
frame of reference |
set of axes by which the position or placement of an object is described |
|
|
allocentric frame of reference |
specify object's location independent of the viewer provide spatial and directional information in unambiguous terms objects are represented only in relation to each other |
|
|
egocentric frame of reference |
specify object's location with respect to the viewer |
|
|
visual egocenter |
the reference point on our body for judging the directions of objects midway between the two eyes |
|
|
transverse plane |
x-axis upper-lower halves roll |
|
|
coronal plane |
y-axis front-back halves pitch |
|
|
median plane |
z-axis left-right halves yaw |
|
|
semicircular canals |
stimulated by rotational body movements vestibular apparatus |
|
|
otoliths |
stimulated by linear body movement vestibular apparatus |
|
|
perception of absolute depth |
retinal image cannot encode depth depth perception by visual cues |
|
|
retinal image size |
optical cue for judging absolute depth if we are familiar with the object, we can easily deduce its distance based on the retinal image |
|
|
ocular cues - accommodation |
accommodating by the thickness of the lens, the brain can deduce the object's distance no ambiguity since accommodating is directly related to object distance accommodative mechanism is more engaged or near objects, negligible contribution to distance perception |
|
|
ocular cues - vergence |
when changing gaze from distant to near objects, eyeballs converge when changing gaze from near to distant objects, eyeballs diverge |
|
|
vergence |
the horizontal rotation of the eyeballs to fixate an object on the foveal region of the retina |
|
|
convergence |
rotate inward |
|
|
divergence |
rotate outward |
|
|
accommodation |
changing the lens blur spot detected on retina if refractive state of eye is not matched for object distance motor command issued from brainstem to ciliary muscle -> changes shape of crystalline lens -> copy of motor command is sent to higher centers of brain that deal with perceptual function |
|
|
pictorial cues |
monocular depth cue based on stationary optical information contained in 2D pictures |
|
|
occlusion |
if one object covers another, relative depth holds that occluded object must lie behind/farther away than the occluding object monocular depth cue acquired skill (between 5-7 months) |
|
|
relative size |
distant objects cast smaller images and visa versa |
|
|
texture gradient |
difference in texture provides a strong depth cue to the visual brain coarse texture arises from near objects finer texture is caused by distant objects |
|
|
linear persepctive |
objects become smaller as they recede |
|
|
aerial perspective |
distant objects viewed through the atmosphere appear fuzzy and washed out image contrast decreases due to light scattering caused by the atmosphere |
|
|
image blur |
objects out of foveal view are blurry the greater the blur, the greater the relative depth in relation to the object we are fixating on |
|
|
kinetic depth |
motion cues generated by the movement of objects in different depth panes closer objects are perceived to move a greater distance than faraway objects |
|
|
motion parallax |
the change in an object's direction of movement caused by self-motion objects located farther than the fixation point move in the same direction as the observer objects located between the fixation point and the observer move in the opposite direction potent cue for relative depth |
|
|
optic flow |
the relative movement of passing objects |
|
|
accretion and deletion |
appearance (accretion) or disappearance (deletion) of objects behind an edge dynamic versions of occlusion |
|
|
size-distance relationship |
as object distance increases, there is a dramatic reduction in retinal image size |
|
|
size constancy - basic aspects |
not directly related to the size of the retinal image we learn about the true physical size of objects through visual experience and use depth information to calibrate a mental impression breaks down under extreme conditions |
|
|
Emmert's law |
perceived size of an afterimage depends on the distance at which it was projected reason: we take into account the distance of the plane on which the afterimage is projected in arriving at a perceived size of the afterimage |
|
|
moon illusion |
the vivid appearance of a very large moon on the horizon compared with the smaller moon perceived when it is directly overhead we believed the horizon is farther away than the sky overhead, so moon right above us seems smaller in reality they are the same size |
|
|
Ponzo illusion |
misconception of relative distance visual system makes size judgements based on the background information contained in the scene an object that casts an identical retinal image but that is believed to lie farther away will be perceived to be larger |
|
|
Ames room illusion |
misperception of relative size see diagram in notes |
|
|
binocular summation |
visual stimulation through both eyes triggers a greater neural activity than stimulation through just one eye |
|
|
advantages of binocular vision |
binocular summation greater visual sensitivity visual field is larger depth perception is 10x more exact |
|
|
binocular fusion |
the combination by the visual brain of the two retinal images to produce a unified picture of the visual scene |
|
|
stereopsis |
the deconstruction of the relative depths of different objects in the visual field responsible for the outstanding depth perception that occurs under binocular viewing conditions (availability of stereoscopic cues + brain's ability to decipher such cues to generate depth perception) |
|
|
Wheatstone's stereogram |
shows how the disparity of retinal images is responsible for the vivid perception of relative depth |
|
|
Vieth-Muller circle |
both eyes are fixated on an object at a particular distance, there exists a theoretical circle in space in which all objects situated in it produce optical images at analogous retinal points in the two eyes theoretical horopter |
|
|
horopter |
the set of environmental points that produce an image an analogous retinal sites for a given fixated point sum of points in space that produce analogous retinal images |
|
|
corresponding retinal images |
images that form at optically analogous points of the two eyes their distances from the fovea are identical use fovea as reference point position of any given retinal image by measuring its distance (d) from the fovea retina labeled in two halves: nasal (n) and temporal (t) |
|
|
retinal disparity |
the difference in the location of the binocular images (D= dt - dn) |
|
|
crossed disparity |
objects located in front of the horopter crease binocular images on non-corresponding retinal points such that dt > dn further from the front of the horopter the object is, the greater the disparity between the two images |
|
|
uncrossed disparity
|
objects located farther away than the horopter create binocular images on non-corresponding retina points such that dt < dn the farther the object is behind the horopter, the greater the disparity between the two images |
|
|
role of binocular neurons |
objects in left visual field trigger neural activity in the right visual cortex (and vice versa) binocular neurons first appear in area V1 |
|
|
disparity selectivity in the visual cortex |
2 ganglion cells at corresponding retinal points feed into a particular binocular neuron in area V1 -> neuron is activated -> sends information to higher parts of the visual brain -> decodes the incoming firing as having originated from an object having the specific disparity condition that coincided with the ganglion cells that fired forms the the fundamental basis by which we perceive relative depth different binocular neurons in area V1 encode all three categories of retinal disparity |
|
|
Panum's fusion area |
the limited range of depth both in front of and behind the horopter in which objects are perceived as single or fused |
|
|
diplopia |
when an object is situated so far behind or so far in front of the horopter that the magnitude of the retinal disparity is outside the range covered by the visual system and double vision appears |
|
|
midline stereopsis |
normal stereoscopic depth perception occurs for objects located along the midline due to integration of visual information between hemispheres occurs through corpus callosum |
|
|
free fusion |
willful crossing/uncrossing of eyes produces a spatial offset in their retinal image locations |
|
|
correspondence problem |
arises from a matching uncertainty between image points in the retina challenge for the visual system is to ensure that a particular object point stimulates the correct circuit so that its true depth, relative to other parts of the object can be captured correctly |
|
|
random-dot stereograms |
a stereogram constructed by randomly assigning black or white dots across the image |
|
|
binocular rivalry |
a phenomenon that arises when two eyes are presented with different images reveals importance of the role of orientation in binocular correspondence at any given time, only one orientation will be perceived, and only briefly--after which the other orientation takes over, creating an oscillation in visual perception between the two orientations |
