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Perceptual processes and development
Several cues to perceive depth. Gibson's direct theory of perception states that all cues can be
directly perceived, but constructivists disagree, they argue that the ability to perceive depth is
learned through experience
Depth cues- divided into 2 types: Binocular cues- 2 eyes & Monocular cues- 1 eye.
Convergence -When focusing on an object, eyes turn inwards to nose.
-Closer the object to face the more eyes turn inwards. Muscles that move then eyes send
signals to the brain.
These provide information about how much eyes have turned- shows depth.
Stereopsis -Each eye has a different viewpoint as in different locations.
-Closer object to the eyes, greater the difference between what your eyes see.
-Look at a distant object; difference would be small so only works with short distances.
Liner Perspective -Parallel lines come closer together with distance.
E.g road goes inwards at the bottom.
Interposition One object blocks the other, the one behind is further away.
Height in visual field - Objects on the ground and higher up in visual field are further away than objects
lower in visual field.
Familiar size Size of the image tells us how far away it is.
Texture gradient -Textured surfaces help to judge depth and distance.
E.g. further away object less texture you can see.
Aerial perspective Dust particles diffuses the light travelling to us, distant objects will look fuzzy & less
distinct than closer ones.
Shadow -Light travels in straight lines & it comes from above so pattern of light and shade
helps to judge depth.
Motion parallax Closer objects appear will move more that those further away.
E.g. Driving a car and side view flashes by but ahead it moves slower.
- Judging the movement of objects, see how far away they are.
Perception of movement
To perceive movement, the visual system has to detect systematic changes in the visual stimulus.
Johansson (1975)- Dressed actors in black and put small lights on their body. Ppts were asked to
observe patterns of lights in a dark room. When actors stood still ppt saw pattern of light as a
random 2D image & didn't make sense of it.
When actors moved ppts were able to see a human figure and what they were doing.
Cutting & Kozlowski (1977) found that 65% of the time ppts were able to correctly guess the sex of
the actors from the way they walked.
This ability to detect and respond t movement and use it to make judgments about shape is an
important perceptual skill.
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The phi phenomenon- The illusion of movement can be created by displaying a series of still
images. When it is rapid we see motion.
Wertheimer (1912)- presented 2 vertical lines together, presentation of lines was alternated, so
only one appreared. When the delay between disappearance of the other was reduced to 20th of a
second, observers only saw one line that moved.
The Autokinetic Effect- Perception of movement when there isn't any or a stimulus to create an
impression of movement.…read more
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Vaneesha Kaur…read more