5. perception

Perception: The Creation of Experience

Perception

• Different people may experience the same sensory information in radically different ways because PERCPETION IS AN ACTIVE, CREATIVE PROCESS in which raw sensory data are organized & given meaning

Processing Functions to create Perception

• Bottom-up processing – the system takes in individual elements of the stimulus & then combines them into a unified perception

• Top-down processing – sensory info is interpreted in light of existing knowledge, concepts, ideas & expectations

CHARACTERISTICS OF PERCEPTION

Perception is Selective: The Role of Attention

• Attention involves 2 processes of selection: focusing on certain stimuli & filtering out other incoming info

• Shadowing

Perception is Selective: The Role of Attention

• Inattentional blindness – the failure of unattended stimuli to register in consciousness

• Environmental & Personal Factors in Attention– Intensity, novelty, movement, contrast &

repetition– Motives & interest– Stimuli that represent a threat to our well-being

Perception have Organization & Structure

• How do we organize the separate parts of our perceptual field into a unified & meaningful whole?

• Figure-ground relations – tendency to organize stimuli into a central or foreground figure & a background

• Gestalt principle of perceptual organization

Gestalt Laws of Perceptual Organization

• Law of similarity – says that when parts of configuration are perceived similar, they will be perceived as belonging together

• Law of proximity – elements that are near each other are likely to be perceived as part of the same configuration

• Law of closure – people tend to close the open edges of a figure or fill in gaps in an incomplete figure so that their identification of the form is more complete than what is actually there

• Law of continuity – people link individual elements together so they form continuous line or pattern that makes sense

Gestalt Laws of Perceptual Organization

Perception involves Hypothesis Testing

• Perceptual schema – a mental representation or image containing the critical & distinctive features of a person, object, event or other perceptual phenomenon

Perception is Influenced by Expectations: Perceptual Sets

• Perceptual set – a readiness to perceive stimuli in a particular way

Stimuli are Recognizable under Changing Conditions: Perceptual Constancies

• Perceptual constancies – allow us to recognize familiar stimuli under varying conditions– Shape constancy – allows us to recognize people &

other objects from many different angles– Brightness constancy – the relative brightness of

objects remains the same under different conditions of illumination

– Size constancy – the perception that the size of objects remains relatively constant even though images on our retina change in size with variations in distance

PERCEPTION OF DEPTH, DISTANCE & MOVEMENT

Depth & Distance Perception

• Retina receives info in 2D; brain translates it in 3D

• Monocular depth cues – require only one eye• Binocular depth cues – require both eyes

Monocular Depth Cues

• Patterns of light & shadow• Linear perspective – perception to that

parallel lines converge as they recede into the distance

• Interposition – in which objects closer to us may cut off part of our view of more distant objects

• Height in the horizontal plane

Monocular Depth Cues

• Texture• Clarity• Relative size• Motion parallax – nearby objects appear to

move faster in the opposite direction than do faraway ones

Binocular Depth Cues

• Binocular disparity – each eye sees a slightly different image

• Convergence – produced by feedback from the muscles that turn your eyes inward to view a close object

Perception of Movement

• Stroboscopic movement (phi phenomenon) – illusory movement when a light is briefly flashed in darkness & then a few milliseconds later, another light is flashed nearby (aka phi phenomenon)

Illusion: False Perceptual Hypotheses

EXPERIENCE, CRITICAL PERIODS & PERCEPTUAL DEVELOPMENT