Cognitive Psychology: Chapter 3: Visual Perception

Vision

From what sense do we receive most of our perceptual input?

Monocular Cues

Needs only one eye

Convergence

The eyes turn inwards to focus on closer (than farther) objects.

Agnosia

a severe deficit in the ability to perceive sensory information.

viewer-centered representation

an individual stores the way the object looks to him or her.

Recognition-by-components (RBC) theory

the belief that we quickly recognize objects by observing the edges of objects and then decomposing the objects into geons.

Geons

"geometrical ions"

Visual object alphabet

36 geons make up the visual alphabet. Objects are made by combining geons at their edges (like LEGO).

Pattern Recognition

A process of identifying a stimulus by recognizing a correspondence between the stimulus and information in long term memory. It is a stage between low-level sensory input and high-level cognition, and it is affected by both bottom-up and top-down processing.

Size Constancy

A tendency for objects to appear the same size regardless of their size projected onto the retina. We take into account an object's apparent distance when judging its size.

Interposition

Also referred to as occlusion: A closer object hides part of a more distant object.

Edge Grouping by Collinearity

An early stage of processing where edges of objects are derived.

Akinetopsia

Associated with damage to the V5 area. Patients with this condition cannot perceive motion visually

Recognition-by-Components (RBC)

Assumes a hierarchy of detectors. The first level detects curves, lines, corners, edges, etc. These feed into the next level that detects geons, which then feed into the next level that detects geon assemblies, which allows specification of relations among geons.

Ganglion cells

Collect information from the retina and combine together to form the optic nerve.

Patterns

Complex and orderly configurations of sensory signals. Sequences of sounds are recognized as words, music, or other noises. Visual features are recognized as objects with color, depth, and motion

Top-Down Processing

Conceptually driven processing. When the interpretation is ambiguous, or when it is possible to parse the features in multiple ways, we use context to guide the parsing mechanism.

Shading

Depth cue concerning the fact the 2D objects do not cast shadows and the assumption that light comes from above our head

Texture Gradient

Details become less clear as you look into the distance.

Structural Description

During this stage, individuals gain access to stored knowledge about the structure (i.e., visual appearance) of objects.

Distinctive Features

Features that distinguish one stimulus from another

Figure-ground separation

Gestaltists claimed that the figure is perceived as having a distinct shape or form and the ground lacks form. This suggests that figure perception and ground perception may be governed by different processes.

Collinearity

Having a common line

by first recognizing the simpler components or elements of the pattern, and then combining the elements into the complex pattern.

How are complex patterns recognized?

Category-Specific Deficit

Impaired for living things but intact for non-living things. Impaired for man-made things (though much less common).

Oculomotor Cues

Kinesthetic, depend on sensations of muscular contraction of the muscles around the eye. Includes convergence and accommodation. Can only provide depth information one object at a time and only work for objects in relatively close distance.

Aerial Perspective

Light scatters as it travels through the atmosphere. More distant objects lose contrast and become hazy.

Feature Binding

Object features that have been extracted during the edge grouping stage and the feature detection stage are combined to form shapes.

Apperceptive agnosia

Object recognition is impaired because of deficits in perceptual processing.

Linear Perspective

Parallel lines pointing away appear progressively closer as they recede into the distance

Associative agnosia

Perceptual processes remain intact but object recognition is impaired because of difficulties in accessing relevant knowledge about objects from memory.

Bottom-Up Processing

Perceptual, data-driven, processing. Objects are recognized by their parts and combined or parsed to create the whole.

Object Discrimination (What)

Pick the correct shape (triangle or rectangle) for a reward. Monkeys with a brain ablasion of the temporal lobe were unable to perform this task

Landmark Discrimination (Where)

Pick the shape closer to the cylinder for a reward. Monkeys with a brain ablasion of the parietal lobe were unable to perform this task

The lateral geniculate nucleus (LGN)

Receives information directly from the retina and sends projections to the primary visual cortex. In addition, it receives many feedback connections from the primary visual cortex.

Featural Processing

Recognition of simple parts and the assembly of those parts into larger wholes.

Binocular Cues

Stereopsis depends on the differences in the images projected on the retina of the two eyes. Only useful for nearby objects

Multiple View Account

Suggests that we store a few prototypical views of an object in our mind and match what we see with those stored views. When an object appears at a viewpoint that does not match what you have stored in memory, your object recognition speed should slow down.

Binocular Vision

The brain combines the discrepancy of images from the left and right eye to provide some information about depth. Actually plays a small role in depth perception.

Visual Agnosia

The impairment of visual object recognition in people who possess sufficiently preserved visual fields, acuity and other elementary forms of visual ability to enable object recognition, and in whom the object recognition impairment cannot be attributed to... loss of knowledge about objects... [The] impairment is one of visual recognition rather than naming, and is therefore manifest on naming and non-verbal tasks alike

The right side

The left hemisphere of the brain receives visual information from what side of the visual field?

Corpus Callosum

Transmits information in between the left and right hemisphere of the brain

Aphasia

Unable to comprehend/produce language

Prosopagnosia

Unable to recognize faces.

Object Agnosia

Unable to recognize objects

Accomodation

Variation in optical power produced by the thickening and thinning of the lens.

Color and form

What are areas V1 and V2 responsible for?

•Linear perspective • Aerial perspective • Texture gradient •Interposition • Shading • Motion parallax

What are the six types of monocular cues?

1) Geons can be recognized from any angle (except accidental angles). 2) Geons are the alphabet of objects. Color and texture are not important for object recognition.

What are two assumptions of RBC?

Showing that different neurons in the visual system specify in detecting different kinds of visual properties

What did David Hubel and Torsten Wiese win the Nobel prize for?

Form, but not color

What is area V3 responsible for?

Color and line orientation

What is area V4 responsible for?

Visual motion

What is area V5 (aka area MT) responsible for?

Patients with damage to the MST have normal low-level motion perception (direction discrimination and speed judgement on a 2D surface), but have difficulty with 3D motion tasks.

What is associated with damage to the MST?

Navigation and to indicate movement of objects relative to the viewer

What is the MST (medial superior temporal) area responsible for?

Lateral Inhibition

When cells are stimulated (activated, excited), they inhibit the activity of neighboring cells. It is an edge enhancement mechanism.

Motion Parallax

When the observer moves sideways, closer objects appear to travel across the visual field faster than more distant objects. Motion parallax is the change of angular position of two stationary points relative to each other as seen by a moving observer.

Our perception of faces are specifically built to detect featural details (and to decode spatial relation among the features) from an upright position. When a face is inverted, that ability is lost.

Why is it difficult to perceive faces from an inverted position?

Ganglion cells

a kind of neuron usually situated near the inner surface of the retina of the eye; receive visual information from photoreceptors by way of bipolar cells and amacrine cells; send visual information from the retina to several different parts of the brain, such as the thalamus and the hypothalamus.

Retina

a network of neurons extending over most of the back (posterior) surface of the interior of the eye. The retina is where electromagnetic light energy is transduced— that is, converted—into neuralelectrochemical impulses

Fovea

a part of the eye located in the center of the retina that is largely responsible for the sharp central vision people tentative hypotheses regarding language, based on their inherited facility for language acquisition and then testing these hypotheses in the environment

View normalization

allows a viewpoint-invariant representation to be derived. This is a controversial idea, because evidence generally suggests that successful object recognition does not require viewpoint-invariant representations.

Horizontal cells

along with amacrine cells, they make single lateral connections among adjacent areas of the retina in the middle layer of cells

Amacrine cells

along with horizontal cells, they make single lateral connections among adjacent areas of the retina in the middle layer of cells

Gestalt approach to form perception

based on the notion that the whole differs from the sum of its individual parts.

Binocular depth cues

based on the receipt of sensory information in three dimensions from both eyes

Direct perception

belief that the array of information in our sensory receptors, including the sensory context, is all we need to perceive anything.

Monocular depth cues

can be represented in just two dimensions and observed with just one eye.

Figure perception

characterized by detail analysis and high resolution

Ground perception

characterized by low resolution and insensitivity to phase information

Photopigments

chemical substances that absorb light, thereby starting the complex transduction process that transforms physical electromagnetic energy into an electrochemical neural impulse; rods and cones contain different types of photopigments; different types of photopigments absorb differing amounts of light and may detect different hues.

Bottom-up theories

data-driven (i.e., stimulus-driven) theories

top-down theories

driven by high-level cognitive processes, existing knowledge, and prior expectations.

Object-centered representation

he individual stores a representation of the object, independent of its appearance to the viewer.

Templates

highly detailed models for patterns we potentially might recognize.

Optic ataxia

impaired visual control of the arm in reaching out to a visual target

Rods

light-sensitive photoreceptors in the retina of the eye that provide peripheral vision and the ability to see objects at night or in dim light; rods are not color sensitive.

Bipolar cell

make dual connections forward and outward to the ganglion cells, as well as backward and inward to the third layer of retinal cells

Perceptual constancy

occurs when our perception of an object remains the same even when our proximal sensation of the distal object changes.

Cones

one of the two kinds of photoreceptors in the eye; less numerous, shorter, thicker, and more highly concentrated in the foveal region of the retina than in the periphery of the retina than are rods (the other type of photoreceptor); virtually nonfunctional in dim light, but highly effective in bright light and essential to color vision.

Feature-matching theories

suggest that we attempt to match features of a pattern to features stored in memory.

law of Prägnanz

tendency to perceive any given visual array in a way that most simply organizes the disparate elements into a stable and coherent form.

Depth

the distance from a surface, usually using your own body as a reference surface when speaking in terms of depth perception.

Context effects

the influences of the surrounding environment on perception.

Optic nerve

the nerve that transmits information from the retina to the brain. Carries the information to the lateral geniculate nucleus (LGN) and then the primary visual cortex (V1).

Constructive perception

the perceiver builds (constructs) a cognitive understanding (perception) of a stimulus; he or she uses sensory information as the foundation for the structure but also uses other sources of information to build the perception.

Perception

the set of processes by which we recognize, organize, and make sense of the sensations we receive from environmental stimuli

Photoreceptors

the third layer of the retina contains the photoreceptors, which transduce light energy into electrochemical energy.

Figure-ground

what stands out from versus what recedes into the background.

Hierarchical model of object recognition

•Edge grouping by collinearity •Feature binding into shapes •View normalization •Structural description •Semantic system