Download We know the most about the visual system so we`ll start there lens 1

We know the most about the visual system so we’ll start there
1. The sense organ gathers and focuses light
2. Photoreceptors are receptor cells on the retina
retina
lens
lens
iris
pupil
retina
The pupil and iris control the
amount of the light
The lens controls the
sharpness of the light
3. The optic nerve connects eye to brain
We can describe the ear and its parts in the
same way that we describe the eye and its parts
1. The outer and middle ear
2. Hair cell
4. The visual cortex (in the occipital lobe) receives and
interprets the nerve signal
3. The Auditory nerve
4. The Auditory cortex
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DISTAL
STIMULUS
(Stimulus in the world)
PROXIMAL
STIMULUS
(Stimulus “in your head”)
(Brain activity)
The proximal
stimulus is
experienced as
a sensation
Psychologists have approached this problem in two ways:
(1) by looking at the most basic stimulus unit
(2) by looking at the whole object/scene
small black cat,
smaller red ball,
This distinction has led psychologists to either:
(1) study the processing limits of individual stimuli
(psychophysicists: bottom-up) OR
(2) to study how entire scenes or objects are processed (Gestalt
and ecological psychologists: top-down).
Psychological Experience
Level of brightness
“Psychophysicists” ask questions like…
1.
What is the minimum stimulus that will create a psychological
experience (a sensation)?
2. How does psychological experience
change when the stimulus changes?
3. What happens when the stimulus
remains constant over time ?
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2. How does psychological experience
change when the stimulus changes?
Brightness Estimate
1. What is the minimum stimulus that will create a psychological
experience?
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10
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0
0
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Physical Energy (Watts)
One unit of physics ≠
One unit of psychology
What is the threshold of a mental experience?
The amount of change in stimulation required before you
notice a change is called the Just Noticeable Difference
3. What happens when the stimulus
present remains constant over time ?
Weber’s Law:
is related to
Level of Stimulation Present
Loudness estimate
JND
A major lesson of psychophysics:
Psychological experience is measurable but there is a difference
between the stimulus and our experience of it
10
5
0
0
5
10
15
Time (minutes)
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Summary
(1) Sensory systems consist of (a) a sense organ, (b)
receptors, (c) nerve cells (neurons), and (d) a brain
area.
(2) Sensory systems turn a distal stimulus (outside the
head) into a proximal stimulus (inside the head) to
create our sensations (what we “feel”).
(3) Study of sensations has focused on basic unit
(bottom up) or whole scene (top down) processing.
(4) Psychophysicists study basic stimuli to determine
how our sensations map onto the amount of the
stimulus present.
(5) Study of psychophysics has shown that with a
change in stimulus, sensations do not change in the
same way.
How do you perceive a 3-D world?
How is the proximal stimulus interpreted?
DISTAL
STIMULUS
(Stimulus in the world)
PROXIMAL
STIMULUS
(Stimulus “in your head”)
(Brain Activity)
PERCEPTUAL
EXPERIENCE
(Interpretation of
the proximal stimulus)
What kind of cues are available from the image on the retina?
CUE #1: Retinal image size
The retina
is a flat
(and curved)
surface
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CUE #2: Interposition (Occlusion)
CUE #3: Linear perspective
Sheba
Bert
Vs.
Vs.
Sheba
Bert
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FIGURE-GROUND
PROBLEM
(3) Another way that psychologists have looked at perception is
terms of the function that a particular object affords.
In other words, objects are perceived in terms of “what they can
be used for”.
APPARENT MOVEMENT
or
PHI PHENOMENON
Summary
(1) While psychophysicists focused on measuring
sensations, other perception psychologists focused on
perceptions (our interpretation of the sensations).
(2) One way psychologists have suggested we do this is
by using clues in the scene to determine the
distance or size of objects in the scene. However,
clues can be ambiguous and illusions may result from
errors in interpreting the clues.
(3) Alternatively, Gestalt psychologists suggested we
interpret scenes in terms of the patterns we detect
in them (organizational processing). Illusions result
from seeing more than one pattern in a scene.
(4) Similarly, ecological psychologists suggest we process
stimuli as a whole based on what they allow us to
do (function).
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