Unformatted text preview: Perception
Can be influenced by:
1. Ambiguous stimuli
3. Previous experience
4. Expectancies Notes on Previous Slide
Notes on Previous Slide Perception is not always about absolute reality. Two people can sense the exact same stimuli or situation and yet perceive them in completely different ways. This is because everybody has their own unique brain shaped by their specific learning histories, emotions, and motivations. In general these 4 influence your perception. Ambiguous stimuli are those that are difficult to figure out. The pictures of “Jesus” and the cow that I showed in class and the next slide are examples of these. Context means that the environment can set you up to perceive something differently. For example, when in a strange place you are more likely to interpret stimuli as dangerous, mean, weird, or offputting. We have talked about # 3 a lot. When you excluded the extra “the” in the classroom demonstration (“Flowers bloom in the the spring”) this was an example. Sometimes perception is based on what you are expecting, you will see what you want to or expect to see. This explains “Jesus” or other religiousshaped stains or other stimuli that draw thousands of people to see them. Form Perception
Form Perception Figure-ground – the
organization of the
visual field into objects
(figures) that stand out
from their surroundings
(ground). Our focus on perception will
again revolve around vision.
Your brain is predisposed to
automatically pick out what
stands out from the background.
Usually this will be another
person, animal, etc. This is
important for survival.
important The above picture represents an ambiguous figureground stimulus. Depending on how you look at it, you either see men walking or white arrows. You can flip which is figure and which is ground. Form Perception
Grouping – the perceptual tendency to organize
stimuli into coherent groups
stimuli Proximity – nearby objects go together Similarity – similar objects go together Continuity – we perceive smooth, continuous
patterns rather than discontinuous
patterns Connectedness – when uniformed or linked we
perceive items as a single unit
perceive Notes on Previous Slide
Notes on Previous Slide
Your brain takes short cuts in perception. One of these is in the perception of form. Our brains automatically group objects in our visual field together. The next slide illustrates some of these concepts. Look at the next slide first, before going on, what jumps out at you?
In the first stimulus you should see three columns rather than 6 individual lines. This is bc some of those lines are closer together than others, so your brain groups based on proximity. On the right you should have “seen” three vertical rows rather than horizontal. Your brain groups the triangles together bc they are similar and same with the circles. This is why vertical rows jump out at you. In the bottom left, you perceived two continuous lines overlapping versus a series of short strait and curved lines. In the last one you see three dumb bells instead of three separate lines and six separate circles. You see this because they are connected. Form Perception
Form Perception Closure – we fill in gaps
to create a complete,
whole Our brains fill in gaps based on
experience. You “see” the white
triangle imposed on the three blue
circles even though no triangle
exists. Your brain does this
because you have lots of
experience with those stimuli and
they are simpler than three
incomplete blue circles. You
rarely encounter these in life.
rarely Depth Perception
Depth Perception Binocular Cues – These require two functional eyes. Retinal disparity – The greater the difference
between the two images the retina receives of
an object, the closer the object is to the viewer.
Pick an object on the wall in front of you. Hold your finger one inch in
front of your eyes on that object. Alternate closing one eye, then the other.
How far does your finger “move”. Now hold your hand out at arms length
and do the same thing. Your finger should have “moved” less in this case.
and Convergence – the extent to which the eyes
converge inward when looking at an object.
converge The more they converge, the closer the object. Depth Perception
Monocular Cues – need only one eye, so a oneeyed person still has some depth perception Interposition – object in front blocks Relative size – if objects same size, the one
that casts a smaller retinal image is farther
away Relative height – objects higher in the field of
vision are farther away
vision Notes from previous slide
Notes from previous slide Pretty simple, if one object blocks another we know that the blocking object is in front of the other and thus, closer to us. The picture of the woman on the horse is intentionally misleading in this respect. We also judge depth by making comparisons. If two objects are relatively the same size, the smaller one is judged to be further away. Look at the baseball players, two slides up. You don’t perceive that some are half as tall as the others, you simply assume that the smaller ones are further away from you. Same with relative height, objects that appear higher in the visual field are probably further away. Think about watching a football game from the student section in the endzone. If USC has the ball and is driving towards the opposite endzone, you see the opposing defenders as being higher in your field of vision than the USC players. Depth Perception
Depth Perception Interposition Depth Perception Relative Size Depth Perception
Monocular Cues Relative motion – As
we move stable objects
move with us
move We also use motion as a depth
cue. If in a car you focus on one
object, say a house, mountain, or
the moon. Objects between you
and that object will appear to
move in the opposite direction
you are traveling. The fixated
object will appear to be moving
with you as will objects behind
that, albeit at a slower pace.
that, Depth Perception
Monocular cues Linear perspective – parallel lines converge
with distance. Think of standing in the middle
of railroad tracks and looking down them.
of Light and shadow – nearby objects reflect
more light to our eyes. Light comes from
above. The further away an object the less
light it reflects to our eyes. Notice in the next slide, light
and shadow make the top right stimulus look like a circle with a bubble but
the bottom left circle looks like it has a crater. Depth Perception
Depth Perception Light and Shadow ...
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- Spring '08
- coherent, Depth perception, Binocular vision