Module 19

Visual Organization and Interpretation

• Perceptual Organization

  • German psychologists noticed that people who are given a cluster of sensations tend to organize them into a gestalt

    • Gestalt: an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.

  • Form Perception

    • Figure and Ground

      • Figure-ground

        • The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).

    • Grouping

      • The perceptual tendency to organize stimuli into coherent groups.

      • Our mind brings order and form to other stimuli by following certain rules for grouping

        • These rules illustrate how the perceived whole differs from the sum of its parts

        • Examples:

          • Proximity

            • We group nearby figures together

          • Continuity:

            • We perceive smooth, continuous patterns rather than discontinuous ones

          • Closure:

            • We fill in gaps to create complete, whole object

        • These principles help us construct reality, but sometimes they lead us astray

  • Depth Perception

    • The ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance.

    • From the two-dimensional images falling unto the retinas, it can organize three-dimensional perceptions that allow us to estimate distance

    • Eleanor Gibson

      • She wondered: Would a toddler peering over the rim perceive the dangerous drop-off and draw back?

        • To answer the question, Gibson and Richard Walk designed a series of experiments using a visual cliff

          • Visual cliff: a laboratory device for testing depth perception in infants and young animals.

          • They tried to convince infants to crawl out onto the glass—an area that looked like the edge of a cliff—but most infants refused to do so, which indicated that they could perceive depth

        • Depth perception is partly innate and partly learning

    • Binocular Cues

      • A depth cue, such as retinal disparity, that depends on the use of two eyes.

      • Binocular cues are used to judge the distance of nearby objects

      • Cues:

        • Convergence

          • The inward angle of the eyes focusing on a near object

        • Retinal disparity

          • A binocular cue for perceiving depth. By comparing retinal images from the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object.

    • Monocular Cues

      • A depth cue, such as interposition or linear perspective, available to either eye alone.

      • Helps us judge (for example) whether a person is 10 or 100 meters away

  • Motion Perception

    • The brain, normally, computes motion based partly on its assumption that shrinking objects are retreating and enlarging objects are approaching, but people are imperfect at motion perception

      • The brain is sometimes tricked into believing what it is not seeing

      • When large and small objects move at the same speed, the large objects appear to move more slowly

    • The brain perceives a rapid series of slightly varying images as continuous movement

      • We construct that motion in our heads

    • Phi phenomenon

      • An illusion of movement created when two or more adjacent lights blink on and off in quick succession.

    • Visual Organization and Interpretation

      • Relative height

        • We perceive objects higher in our field of vision as farther away

      • Relative size

        • If we assume two objects are similar in size, most people perceive the one that cast the smaller retinal images as farther away

      • Interposition

        • If one object partially blocks our view of another, we perceive it as closer

      • Relative motion

        • As we move, objects that are actually stable may appear to move

      • Linear perspective

        • Parallel lines appear to meet in the distance

      • Light and shadow

        • Shading produces a sense of depth consistent with our assumption that light comes from above

  • Perceptual Constancy

    • Perceiving objects as unchanging (having consistent color, brightness, shape, and size) even as illumination and retinal images change.

    • Regardless of the viewing angle, distance, and illumination, we can identify people and things in less time than it takes to draw a breath

    • Color and Brightness Constancies

      • Our experience of color depends on an object’s context

      • Color constancy

        • Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.

      • Because we construct our perceptions, we can simultaneously accept alternative objective and subjective realities

      • Brightness constancy similarly depends on context

        • We perceive an object as having a constant brightness even as its illumination varies

        • This perception of constancy depends on relative luminance

          • The amount of light an object reflects relative to its surroundings

      • Context governs our perceptions

    • Shape and Size Constancies

      • Sometimes an object whose actual shape cannot change seems to change shape with the angle of our view

      • Size constancy helps us perceive an object as having an unchanging size, even while our distance from it varies

      • Even in size-distance judgements, the object’s context is always considered

      • The interplay between perceived size and perceived distance helps explain several well-known illusions

      • Perpetual organizations applies to other senses as well

        • Listening to our own language, we can automatically hear distinct words

        • We can organize a string of letters into words that make an intelligible phrase

          • THEDOGATEMEAT is more likely seen as “the dog ate meat”, rather than “the do gate me at”

• Perceptual Interpretation

  • Immanuel Kant

    • German philosopher

    • Maintained that knowledge comes from our inborn ways of organizing sensory experiences

  • John Locke

    • British philosopher

    • Argued that through our experiences we also learn to perceive the world

  • Experience and Visual Perception

    • Restored Vision and Sensory Restriction

      • William Molyneux

        • Wondered whether “a man born blind, and now adult, taught by his touch to distinguish between a cube and a sphere” could visually distinguish the two

          • John Locke answered nom as the man would never have learned to see the difference

          • Was put to test with adults who were born blind but later gained sight, but remained unable to visually recognize objects

    • Perceptual Adaptation

      • The ability to adjust to changed sensory input, including an artificially displaced or even inverted visual field.

      • Humans can adapt to distorting lenses quickly

        • Even when given a lens that turns the world upside down

        • Experience guides, sustains, and maintains the brain pathways that enable our perceptions

Smaller text = Bolded vocab in the textbook

Bolded = Headings