Perception

Perception

Dr.safeyya Adeeb Alchalabi

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.

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.


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).

Perceptual constancy

Shape constancy
Is the tendency to interpret the shape of an object as constant, even when changes on the retina.

Perceptual constancy

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.

Depth perception

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.

Gestalt psychology

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.

Gestalt psychology

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.

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)].


Figure-ground relationships

Reversible figures

In which the figure and the ground seem to switch back and forth.

Gestalt principles

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.

Gestalt principles of grouping

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).


Gestalt principles of grouping
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).

Gestalt principles of grouping

Closure
is the tendency to complete figures that are incomplete.
(we perceive figures with gaps in them to be complete).

Gestalt principles of grouping

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).

Gestalt principles of grouping

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.


Perceptual illusion

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.

Muller-Lyer illusion

Moon illusion

Perceptual set (perceptual expectancy)

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.

Factors influencing Perception

Factors in the perceiver
Attitudes
Motives
Interests
Experience
Expectations


Factors in the Target
Novelty
Motion
Sounds
Size
Background
Proximity
Similarity

Factors in the situation

Time
Work Setting
Social Setting

Perceptual Process

Receiving Stimuli
(External & Internal)

Selecting Stimuli

External factors : Nature,
Location,Size,contrast,
Movement,repetition,similarity
Internal factors : Learning,
needs,age,Interest,


Organizing
Figure Background ,
Perceptual Grouping
( similarity, proximity,
closure, continuity)

Interpreting

Attribution ,Stereotyping,
Halo Effect, Projection

Response

Covert: Attitudes ,
Motivation,
Feeling
Overt: Behavior

Factors influencing perception

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.


Disorder of perception
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

Auditory hallucinations (voice, sound, noise).
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).

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
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

Thank you