Binocular Cues for Depth Perception

•  The ability to judge distance and depth such as retinal disparity and convergence with two eyes, which are slightly apart from each other.
•  Our eyes are slightly apart from each other having a distance of about 2 ½ inches or 6 cm, so the images that fall on the two retinas are slightly different.
•  These two slightly different images are then integrated and processed by the brain, but it does not ignore the possibility of difference in images__ known as “ binocular disparity”.

i.  Retinal/ Binocular Disparity
•  The cue to depth perception, the greater the disparity (difference) between the two images the retinas receive of an object, the closer the object seems to us___ this disparity allows the brain to judge distance.
 

•  This can be proved with the help of simple experiments done by you. i.e. hold a pencil directly in front of your nose; the retinas of yours will receive different views/ images. Now make them closer firstly to one eye and then to the other. At greater distance, the disparity is smaller.
 

•  This discrepancy of the two images that falls on the retinas varies with respect to the distance from which the object is being perceived___ used for determining distance e.g. if we see two objects in which one is considerably closer than the other, the retinal disparity will be greater and we perceive the greater depth between the two.
 

•  On the contrary, if the two objects were at similar distance, the retinal disparity will be minor/ smaller and we perceivethe objects at similar distance.
 

•  Movie directors use these phenomena in order to create depth illusions by using two cameras, spaced highly apart, to produce slightly different images, each image
for each eye.
 

•  In 3-D movies, the two images are presented simultaneously which produces a double image; special glasses are worn for this purpose to provide us with the genuine sense of the depth phenomena.Convergence and Accommodation

A binocular cue for depth perception that illustrates, that when we assume that the two objects are of same size, the one that produces a relatively smaller image will be perceived as distant. It is a neuromuscular cue in which the more the eyesconverge inwards, the nearer the object seems.
The eye lens becomes thicker due to the activation of ciliary muscles to focus on the nearer object____ the degree of activation of ciliary muscles gives us the cue to depth.
Convergence and accommodation are only effective at close distances and can tell only the distance to a single object in the visual field.
Selective Attention
•  Perceptual process in which the person chooses the stimulus which he is interested in; paying attention to only the stimulus of interest.

•  Humans give attention to the objects that are exceptionally bright, loud, novel, or high in contrast___ we are also motivated to give attention to the objects that are meaningful as well as e.g. if we are thirsty, we will give more attention to water and the like.
 

•  Advertisers extensively use this phenomena of selective attention using bright contrasts, high volumes and more rapid speech than usual__ and most importantly broadcast at that time when people are particularly sensitive to their content e.g. the food- related ads are shown at lunch or dinner times.Stroop Task
 

•  Difficult and frustrating exercise in which one is confronted with two powerful and competing stimuli___ the meaning of the word and the colors in which they are written e.g. I LIKE YOU, if written in red ink.
 

•  In these cases, it has been observed the people pay more attention to the reading/ content of the stimulus rather than the color from which it has been written (because they are experienced with reading than with naming colors).

b.  Dichotic Listening
•  A procedure in which individual wears earphones in which different messages are sent to each ear at the same time.
 

•  After hearing the stimuli, the individual is asked to reproduce them aloud as it comes to one ear: “ shadowing”.
 

•  In this process, individual can easily identify the talking person as man or woman and whether change in voices takes place during the message or not.
 

•  Experiments suggest that although people pay full attention to one stimulus at a time, they also pay some level of attention to the other stimuli as well; it shows the possibility of learning something although being unaware of it.The phenomenon of selective attention is of particular importance for the people who have to constantly monitor e.g. such as pilots, traffic controllers, rescue workers, and firemen.

Form-Perception
•  A perceptual phenomenon in which we perceive the shape, form or pattern of any object___ give name to objects ashouse, tree, table, chair etc
•  Mainly it involves two important principles:
•  Figure- ground relationship
•  Contours
 

Figure- Ground Relationship
•  Our perceptual tendency to see objects with the foreground as well as the background___ the object is being recognizedwith respect to its back ground e.g. Black board and chalk, car parked in front of a wall, painting against the wall etc.
 

•  Contrasting figures and their grounds are early and quickly perceived
 

•  It is a vise- versa relationship i.e., figurecannot be observed without a ground and ground cannot be recognized without having a figure.

Contours
•  Perceptual phenomenon in which we are able tomaintain a difference of the form from its background due to the perception of contours e.g. In observing the paper, which has two colors, white and black__ there is no contour at all. But as it becomes lighter rather than becoming dark, a person can simply identify the difference. And when the difference is much apparent, we simply divide into two parts as light and dark and skipdifferent shades as lighter or darker____ where brightness changes abruptly, we perceive contours.