PERCEPTION II
Depth Perception
• Depth perception is the perceptual tendency/ ability to see objects in three dimensions,
although the image that falls on the retina of the eye is two-dimensional; thus enabling us
to perceive distance.
• “Depth Perception” is the skill to perceive depth and distance e.g. we are able to judge the distance
of the incoming car, height of the cliff or of a roof top, size of an object, weight of a sand bag etc,
in a glance, just by having a look at it.
• This sort of perception is largely due to the factthat we have two eyes which are slightly distant
from each other, so the brain integrates the two slightly different images and combines them into
one consolidated view; However the differences in images or ‘Binocular Disparity’ is not ignored
by the brain.Eleanor Gibson and Richard Walk discovered this phenomena in 1960 by using the
miniature cliff with a drop- off covered by sturdy glass.
• Placed the young infants of 6- 14 months at the edgeof visual cliff. Their mothers motivated them
to crawl on the glass, but most of them refused to do so, indicating that they could perceive
depth__ this may be due to the fact that they learned to perceive depth in the crawling age.
Physiological depth cues are formed by our visual system withthe help of muscular movements or
adjustments. It is yet difficult to tell how these cues contribute to the depth perception. The
adjustments, which the eyes and eye muscles make, are assumed to be of weak nature. These include:
accommodation and convergence.
The psychological depth cues: are based on the interpretation and analysis of the retinal image that is
caused by the working of the visual cortex in the brain. Depth Cues to Perception
There are two important cues for the perception of depth. These include:
I. Monocular cues for depth perception.
II. Binocular cues for depth perception.
I.Monocular Cues for Depth Perception
• Also known as “ pictorial cues” because painters use these cues in order to tell about
depth; these lead to three- dimensional information.
• These generate the ability to judge distance and depth suchas linear perspective and
interposition with only one eye.
• Depth and location can be perceived with single eye also.
i. Relative motion
• A monocular cue for perceiving depth and distance in which when we move, the objects at different distances change their relative positions with the visual image___ with those that are closest seem to be moving faster.
Relative Size
The monocular cue for depth perception in which we assume that the two objects are similar in size, the
one that make the smaller image appears to be more distant.
Interposition
A monocular cue for perceiving depth in which the nearer objects partially block/ hinder our image of the
more distant objects.
Relative Height
• A monocular cue to depth perception and distance in which higher objects appear to be more distant.
• Can be explained by doing practically as we are moving in car, train, bus etc. Fixate your gaze at
some point (fixation point)___ say a tree, __ the objects that are closer than the tree seems to be
moving backwards and also seem to move faster. The objects that are beyond the fixation point seem to move along but at lower speed and seemas farther away. Brain has the capability to compute these speed and distance clues in order to perceive distances.
Linear Perspective
• The monocular cue for the perception of depth and distance in which two parallel lines seem to be
converging at some point indicating increasing distance.
• Rail road tracks, highway tracks etc appear to be converging at some distance and so, contribute to the
rail- crossing accidents by making people to over estimate the train’s distance: a massive train size
makes the perception that it is moving slowly.
Linear Perspective
• The monocular cue for the perception of depth and distance in which two parallel lines seem to be
converging at some point indicating increasing distance.
• Rail road tracks, highway tracks etc appear to be converging at some distance and so, contribute to the
rail- crossing accidents by making people to over estimate the train’s distance: a massive train size
makes the perception that it is moving slowly.
Relative Brightness
A monocular cue for depth perception in which the dimmer objects seem to be more distant.
Nearby objects seem to reflect more light than the farther ones. When going for a walk in a thick-fog
morning, one may judge distance wrongly as due to fog the objects may be perceived to be farther than they
do on the clear shiny morning. That is why they contribute to increasing accidents.
Light and Shadow
Perceptual phenomenon for the perception of depth and distance in which when light strikes an irregular
object, certain parts are brightly illuminated whereas others lay in shadow. These shadowed parts tell us
about the depth of the parts concerned___ painters use this phenomenon when portraying something on
the canvas such as human face and its various structures.
Texture Gradient
An American psychologist, James J. Gibson wasthe ever first individual who emphasized the
importance of texture gradient for perceiving depth.
Mainly applied to textures (structures) of surfaces and arises when we observe the surface when in slant
rather than from a straight angle or from above. Pictorial Cues for Depth Perception
Monocular cues are used for the perception of depth and distance
• We can get an extensive 3-D impression in 2-D pictures on a flat surface
Atmospheric Perspective
Particles and vapors in the atmosphere result/ cause the scattering of light that makes a very distant
surface appear hazy.
The other techniques they use are;
a. Occlusion: near objects overlap far surfaces.
b. Relative height and size:objects further away from the horizon seem nearer and larger objects seem closer.
c. Linear perspective:provides a strong cue to distance that can effect perception.
d. Shading:provides a cue for shape rather than distance.
Motion Parallax
The change in the position of the retinal image with the side-to-side movement of the head; providing a cue
to the distance.
Occurs when objects are at different distances and weare also moving at different rates when in motion.
The object nearer to the person appears to move backward but the more distant objects appears to be static as we move. The rate of an object’s movement provides a cue to its distance.
Although motion plays an important role in depth perception, the perception of motion is an important
phenomenon in its own right. It allows a baseball outfielder to calculate the speed and trajectory of a ball
with extraordinary accuracy. Automobile drivers rely on motion perception to judge the speeds of other cars
and avoid collisions. A cheetah must be able to detect and respond to the motion of antelopes, its chief
prey, in order to survive.
How does your brain know which movement on the retina is due to your own motion and which is due to
motion in the world? Understanding that distinction is the problem that is faced by psychologists who want
to explain motion perception.
• Depth perception is the perceptual tendency/ ability to see objects in three dimensions,
although the image that falls on the retina of the eye is two-dimensional; thus enabling us
to perceive distance.
• “Depth Perception” is the skill to perceive depth and distance e.g. we are able to judge the distance
of the incoming car, height of the cliff or of a roof top, size of an object, weight of a sand bag etc,
in a glance, just by having a look at it.
• This sort of perception is largely due to the factthat we have two eyes which are slightly distant
from each other, so the brain integrates the two slightly different images and combines them into
one consolidated view; However the differences in images or ‘Binocular Disparity’ is not ignored
by the brain.Eleanor Gibson and Richard Walk discovered this phenomena in 1960 by using the
miniature cliff with a drop- off covered by sturdy glass.
• Placed the young infants of 6- 14 months at the edgeof visual cliff. Their mothers motivated them
to crawl on the glass, but most of them refused to do so, indicating that they could perceive
depth__ this may be due to the fact that they learned to perceive depth in the crawling age.
Physiological depth cues are formed by our visual system withthe help of muscular movements or
adjustments. It is yet difficult to tell how these cues contribute to the depth perception. The
adjustments, which the eyes and eye muscles make, are assumed to be of weak nature. These include:
accommodation and convergence.
The psychological depth cues: are based on the interpretation and analysis of the retinal image that is
caused by the working of the visual cortex in the brain. Depth Cues to Perception
There are two important cues for the perception of depth. These include:
I. Monocular cues for depth perception.
II. Binocular cues for depth perception.
I.Monocular Cues for Depth Perception
• Also known as “ pictorial cues” because painters use these cues in order to tell about
depth; these lead to three- dimensional information.
• These generate the ability to judge distance and depth suchas linear perspective and
interposition with only one eye.
• Depth and location can be perceived with single eye also.
i. Relative motion
• A monocular cue for perceiving depth and distance in which when we move, the objects at different distances change their relative positions with the visual image___ with those that are closest seem to be moving faster.
Relative Size
The monocular cue for depth perception in which we assume that the two objects are similar in size, the
one that make the smaller image appears to be more distant.
Interposition
A monocular cue for perceiving depth in which the nearer objects partially block/ hinder our image of the
more distant objects.
Relative Height
• A monocular cue to depth perception and distance in which higher objects appear to be more distant.
• Can be explained by doing practically as we are moving in car, train, bus etc. Fixate your gaze at
some point (fixation point)___ say a tree, __ the objects that are closer than the tree seems to be
moving backwards and also seem to move faster. The objects that are beyond the fixation point seem to move along but at lower speed and seemas farther away. Brain has the capability to compute these speed and distance clues in order to perceive distances.
Linear Perspective
• The monocular cue for the perception of depth and distance in which two parallel lines seem to be
converging at some point indicating increasing distance.
• Rail road tracks, highway tracks etc appear to be converging at some distance and so, contribute to the
rail- crossing accidents by making people to over estimate the train’s distance: a massive train size
makes the perception that it is moving slowly.
Linear Perspective
• The monocular cue for the perception of depth and distance in which two parallel lines seem to be
converging at some point indicating increasing distance.
• Rail road tracks, highway tracks etc appear to be converging at some distance and so, contribute to the
rail- crossing accidents by making people to over estimate the train’s distance: a massive train size
makes the perception that it is moving slowly.
Relative Brightness
A monocular cue for depth perception in which the dimmer objects seem to be more distant.
Nearby objects seem to reflect more light than the farther ones. When going for a walk in a thick-fog
morning, one may judge distance wrongly as due to fog the objects may be perceived to be farther than they
do on the clear shiny morning. That is why they contribute to increasing accidents.
Light and Shadow
Perceptual phenomenon for the perception of depth and distance in which when light strikes an irregular
object, certain parts are brightly illuminated whereas others lay in shadow. These shadowed parts tell us
about the depth of the parts concerned___ painters use this phenomenon when portraying something on
the canvas such as human face and its various structures.
Texture Gradient
An American psychologist, James J. Gibson wasthe ever first individual who emphasized the
importance of texture gradient for perceiving depth.
Mainly applied to textures (structures) of surfaces and arises when we observe the surface when in slant
rather than from a straight angle or from above. Pictorial Cues for Depth Perception
Monocular cues are used for the perception of depth and distance
• We can get an extensive 3-D impression in 2-D pictures on a flat surface
Atmospheric Perspective
Particles and vapors in the atmosphere result/ cause the scattering of light that makes a very distant
surface appear hazy.
The other techniques they use are;
a. Occlusion: near objects overlap far surfaces.
b. Relative height and size:objects further away from the horizon seem nearer and larger objects seem closer.
c. Linear perspective:provides a strong cue to distance that can effect perception.
d. Shading:provides a cue for shape rather than distance.
Motion Parallax
The change in the position of the retinal image with the side-to-side movement of the head; providing a cue
to the distance.
Occurs when objects are at different distances and weare also moving at different rates when in motion.
The object nearer to the person appears to move backward but the more distant objects appears to be static as we move. The rate of an object’s movement provides a cue to its distance.
Although motion plays an important role in depth perception, the perception of motion is an important
phenomenon in its own right. It allows a baseball outfielder to calculate the speed and trajectory of a ball
with extraordinary accuracy. Automobile drivers rely on motion perception to judge the speeds of other cars
and avoid collisions. A cheetah must be able to detect and respond to the motion of antelopes, its chief
prey, in order to survive.
How does your brain know which movement on the retina is due to your own motion and which is due to
motion in the world? Understanding that distinction is the problem that is faced by psychologists who want
to explain motion perception.
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