1
Perception
]
د.صفية
\
م
1
[
Perception
Is the method by which the brain takes all the sensations a person
experiences at any given moment and allows them to be interpreted in
some meaningful fashion.
Imp
2
But what does
" meaningful "mean? How do we know what information
is important and should be focused on?
Selective Attention:
process of discriminating between what is important
& is
irrelevant , and is influenced by motivation.
ALL OF THIS IS CALLED Psychophysics
Psychophysics can be defined as, the study of how physical stimuli
are translated into psychological experience.
In order to measure these events ,psychologists use THRESHOLDs
Threshold - a dividing line between what has detectable energy and
what does not.
Difference Threshold - the minimum amount of stimulus intensity
change needed to produce a noticeable change.
the greater the intensity (ex., weight )of a stimulus, the greater the
change needed to produce a noticeable change.
3
Constancies:
Perceptual constancy:
Something that remains the same, the property of
remaining stable and unchanging.
Perceptual constancy:
Size constancy
The tendency to interpret an object as always being the same size,
regardless of its distance from the viewer (or the size of the image
it casts on the retina).
Shape constancy
Is the tendency to interpret the shape of an object as constant,
even when changes on the retina.
Brightness constancy
The tendency to perceive the apparent brightness of an object as
the same even when the light conditions change.
Depth perception
The capability to see the world in three dimensions.
(Depth perception the ability to recognize depth or the relative
distances to different objects in space).
It seems to develop very early in infancy, if it is not actually
present at birth.
4
Gestalt principles
The tendency to group objects and perceive whole
shapes.
Gestalt psychology
Back to Germany, by the psychologist Max Wertheirmer.
Wertheirmer believed that psychological event such as perceiving
and sensing could not broken down in to any smaller elements
and still be properly understood, so perception can only be
understood as whole, entire event.
“The whole is greater than the sum of its parts”
Wertheirmer and others believed that people naturally seek out
patterns (“whole”) in the sensory information available to them.
Wertheimer and others devoted their efforts to studying
sensation and perception in their new perspective, Gestalt
psychology.
(Gesh-TALT) is a German word meaning “an organized whole” or
“configuration”, which fit well with the focus on studying whole
patterns rather than small pieces of them.
Today, Gestalt ideas are part of the study of cognitive psychology,
a field focusing not only on perception but also on learning,
memory, thought processes, and problem solving.
The Gestalt approach has also been influential in psychological
therapy, becoming the basis for a therapeutic technique called
Gestalt therapy.
5
Gestalt principles
Figure-ground relationships
Refer to the tendency to perceive objects or figures as existing on
a background.
[Organization depends what we see as figure (object) and what we
perceive a ground (context)].
Reversible figures
In which the figure and the ground seem to
switch back and forth.
6
Figure-ground relationships
People seem to have a preference for picking out figures from
background even as early as birth.
Gestalt principles of grouping
The Gestalt principles of grouping include four types:
similarity,
proximity,
continuity, and
closure.
Proximity (nearness)
Another very simple rule of perception is the tendency to perceive
objects that are close to one another (in space or time) as part of
the same grouping (or belong together).
7
Similarity
Refers to the tendency to perceive things that look similar as
being part of the same group.
(Objects that have similar characteristics are perceived as a unit).
Closure
is the tendency to complete figures that are incomplete.
(we perceive figures with gaps in them to be complete).
8
Continuity
It refers to the tendency to perceive things as simply as possible
with continuous pattern rather than with a complex, broken-up
pattern.
(we tend to perceive figures or objects as belonging together if they
appear to form a continuous pattern).
Common region
The tendency is to perceive objects that are in a common area or
region as being in a group.
Perceptual illusion
A false perception of actual stimuli involving a misperception of size,
shape, or the relationship of on element to another.
9
Feature detectors
They respond to specific features of a stimulus.
Simple cells: Neurons in the primary visual cortex that respond
best to bars of light of a specific orientation.
Complex cells: which respond to orientation and movement.
End-stopped cells : which respond best to corners, curvature, or
sudden edges.
11
11
12
Influances on perception:
Inattentional blindness
The phenomenon in which we miss an object in our field of vision
because we are attending to another.
Social perception
Facial expressions, the visual cues for emotional perception, often
take priority over the auditory cues associated with a person’s
speech intonation and volume, as well as the actual words
spoken.
13
Factors influencing Perception
Factors in the perceiver
Attitudes
Motives
Interests
Experience
Expectations
14
Factors in the Target
Novelty
Motion
Sounds
Size
Background
Proximity
Similarity
Factors in the situation
Time
Work Setting
Social Setting
15
Factors influencing perception
Selective perception:
people selectively interpret what they see on the basis
of their interests,background,experience
& attitude.
Halo effect:
Drawing a general impressions about an individual on
the basis of a single characteristics.
16
Disorder of perception [very important all]
I.sensory distortion
1. Changes in intensity
( hyperacusis)
2. Change in quality ( xanthopsia
, erythropsia,chloropsia)
3. Change in special form (micropsia
, macropsia)
II. Sensory deception
Hallucinations and illusions are often classed together under the
name of psychsensory disorders
.
Hallucination:[imp]
Auditory hallucinations (voice, sound ,nois( [
imp]
Second-person hallucinations: voice speaking to the person
addressing him as “you.”
Third-person hallucinations: voice talking about the person
as “he” or “she:”
Thought echo: hearing one’s own thoughts spoken aloud.
Visual hallucinations (images/sights(
Olfactory hallucinations (smell/odour(.
Gustatory hallucinations (taste(
Somatic hallucinations (visceral and other internal sensations (
.
Tactile hallucinations (touch/surface sensations(
17
[imp]
Formication :’a feeling that animals are crawling over the body;
not uncommon in acute organic states.
‘Cocaine bug :’formication occurring with delusions of
persecution; in cocaine psychosis .
Extracampine hallucinations :a hallucination which is outside the
limits of the sensory field.
‘ Negative autoscopy :’the pt. looks in the mirror and sees no
image; in organic states.
Internal autoscopy :the subject sees his/her own internal organs.
Hypnagogic hallucinations :hallucinations when falling asleep.
Hypnopompic hallucinations :hallucinations when waking from
sleep.
Insufficiency Of Perception[not imp.]
Insufficiency of perception in its slightest degree may be met with
in states of depression, at the onset of confusional states, etc. All
external impressions are vague, uncertain, and strange. The
patients complain that everything has changed in them and
around them: objects and persons have no more their usual
aspect; the sound of their own voice startles them.
Finally, complete paralysis of one or several forms of
psychosensory activity is observed in connection with profound
disorders of consciousness, as in mental confusion of the
stuporous form.
Insufficiency of perception constitutes an important element of clouding
of consciousness
18
:مالحظة
هنالك بعض الصور لم تدرج في المحاضرة الرجاء مراجعة البوربوينت
Important:
Definition of perceptionp:1
Disorder of perception
p:16
Hallucination
p:16