Chapter 3: Visual Perception

Difference between each eye's view of a stimulus; provides important information about distance relationships in the world.

binocular disparity

Cells that receive input from photoreceptors which excite the ganglion cells.

bipolar cells

Neurons that have a donut shaped receptive field.

center-surround cells (dot detectors)

How does light enter the eye?

light--> cornea--> lens--> retina

Parallel lines seem to converge as they get farther away from viewer (looking down a hallway).

linear perspective

When the muscle tightens, the lens bulges somewhat, creating the proper shape for focusing the images of ___________ objects. When the muscle relaxes, the lens returns to a flatter shape, allowing the proper focus for objects ____________.

nearby; farther away

Why is single-cell recording useful?

-allows us to see the frequency of firing -we can then vary the inputs to see what pattern of firing a stimulus produces

What are other receptor specializations when referring to receptive fields?

-angles -motion -direction of movement -corners

What are the different types of perceptual constancies?

-brightness constancy -size constancy -shape constancy

What are the 4 types of monocular cues?

-lens adjustment -pictorial cues -linear perspective -texture gradient

Describe the receptive field of edge detectors.

-some fire at highest rate when horizontal edge is present -others fire at highest rate when vertical edge is present -still respond to other orientations, but rate is slower the further the orientation is from the "preferred" orientation

Which elements help solve the binding problem?

-spatial position -neural synchrony -attention

What is an advantage of parallel processing?

-speed--> brain areas trying to discern the shape of the incoming stimulus don't have to wait until the motion analysis or color analysis is complete -all analyses go forward immediately -mutual influence among multiple systems

Describe the receptive field of center-surround cells.

-stimulus in center of receptive field leads to faster firing rates -stimulus in surrounding areas of receptive field leads to slower, below baseline firing rates -stimulus covering the entire receptive field has same effect as no stimulus

The primary visual projection area which is located in the occipital lobe.

Area VI

Which two neuropsychologists were awarded the Nobel Prize for their exploration of the mammalian visual field--> documented the existence of specialized neurons within the brain, each of which has a different receptive field.

David Hubel and Torsten Weisel

The ability to see fine detail.

acuity

What does damage to the what system lead to?

agnosia

People with this condition have otherwise normal vision, but can't perceive motion (unable to detect when an object changes location, only before and after conditions)

akinetopsia

The task of reuniting the various elements of a scene, elements that are initially addressed by different systems in different parts of the brain.

binding problem

There are neither rods nor cones at the retina's _____________, the position at which the neural fibers make up the optic nerve exit the eyeball.

blind spot

Being able to correctly perceive brightness of objects whether they are illuminated by dim light or strong light.

brightness constancy

How is light focused onto the retina?

by the cornea and lens

Gestalt principle in which an object is complete or a space is not completely closed; if enough of the shape is indicated, people will see the whole by filling in the missing information.

closure

Photoreceptors that are responsible for color vision, spatial resolution, and acute details.

cones

Perceivers correctly detect features present in visual display, but they make mistakes about how features are bound together.

conjugation errors

When we overload a perceiver's attention, they often make ___________.

conjunction errors

Lateral inhibition produces a ___________ (i.e. central square in figure is surrounded by dark squares and the contrast makes it look brighter).

contrast effect

Transparent covering over the eye that serves as a barrier between between the inner eye and the outside world.

cornea

What does damage to the where system lead to?

difficulties reaching for objects

Features of the stimulus that indicate an object's position.

distance cues

Neurons that fire at their maximum only when a stimulus containing an edge of just the right orientation appears within their receptive fields.

edge detectors

Lateral inhibition gives rise to ____________, which is when cells in the visual system give exaggerated responses to the edges of surfaces.

edge enhancement

Explain the process of lateral inhibition.

eye--> photoreceptors--> bipolar cells--> optic nerve--> lateral geniculate nucleus--> area VI

The lens will focus images perfectly on this small indentation in the back of the eye.

fovea

Where are cones concentrated?

fovea

Cells that spread across the entire retina and whose axons converge to form the optic nerve.

ganglion cells

Gestalt principle in which continuaton occurs when the eye is compelled to move through one object and continue to another object, preferring to see a single continuous figure rather than separate lines (we perceive the simplest path).

good continuation

Example of neural synchrony.

if neurons detecting a vertical line are firing in synchrony with those signaling movement, then these attributes are interpreted as belonging to the same object

Blocking of your view of one object by some other object tells you the object in front is closer.

interposition

The colored part of the eye; connected to muscles that control the size of the pupil.

iris

What is the significance of the spatial position?

it allows you to overlay the map of which forms are where on top of the map of which colors are where to get the right colors with the right forms, and likewise showing which motion patterns are where

How does attention help solve the binding problem?

it plays a key role binding together the separate features of a stimulus

Part of the thalamus and is the first top in the brain for visual information from they eyes.

lateral geniculate nucleus

A pattern in which cells, when stimulated, inhibit the activity of neighboring cells.

lateral inhibition

The curved, transparent structure that is used to focus images.

lens

Muscles adjust shape of lens to produce a sharply focused image in the retina.

lens adjustment

When light levels are ______, the pupil will become dilated, or expanded, to allow more light to enter the eye. When light levels are _______, the pupil will constrict, or become smaller, to reduce the amount of light that enters the eye.

low; high

Depth cues that depend only on what each eye sees by itself.

monocular distance cues

Distance cue in which whenever you move your head, images projected by objects in your view move across your retinas (projected images of nearby objects move more than those of distant ones).

motion parallax

The visual areas processing features of the same object fire in synchronous rhythm with each other.

neural synchrony

As you move toward or away from an object, pattern of stimulation across entire visual field changes.

optic flow

Carries information from eyeballs to the brain.

optic nerve

The visual system relies on ______________, with many different steps/analysis going on simultaneously.

parallel processing

The ability to perceive constant object properties (sizes, shapes, etc.) even though sensory information about these attributes changes when viewing circumstances change.

perceptual constancy

Where are rods concentrated?

periphery of the retina--> allows you to see dim light better in your peripheral vision

Specialized neural cells that respond directly to incoming light.

photoreceptors

Patterns that can be represented on a flat surface to create the sense of a 3D object or scene.

pictorial cues

Gestalt principle in which we group closer together elements, separating them from those farther apart (rows of dots with spaces between them).

proximity

The small opening in the eye through which light passes (size changes with light levels as well as emotional arousal).

pupil

Using single-cell recording allows researchers to map out the ______________, which is the size and shape of the area in the visual world to which the cell responds.

receptive field

Visual stimulus that has more than 1 interpretation, but only one can be seen at a time.

reversible (ambiguous) figures

Long, narrow photoreceptors that are sensitive to low levels of light, contribute to your sense of brightness, and allow you to see basic shapes and forms.

rods

The two types of photoreceptors found on the retina.

rods and cones

Parallel processing is usually contrasted with __________, in which steps are carried out one at a time.

serial processing

Being able to correctly perceive an object's shape despite changes in the retinal image.

shape constancy

Gestalt principle in which similar elements are visually grouped, regardless of their proximity to each other (rows of red dots and rows of green dots).

similarity

Gestalt principle in which our minds perceive everything in the simplest forms.

simplicity

A technique that can record, moment-by-moment, the pattern of electrical charges within a neuron.

single-cell recording

Being able to correctly perceive an object's size despite changes in retinal-image size created by changes in viewing distance.

size constancy

The visual areas processing features like shape, color, and motion each know the ___________ of the object.

spatial posititon

Changes in texture can give clues about distance and spatial arrangements.

texture gradient

How do Gestalt psychologists view perception?

the perceptual whole is often different than the sum of its parts (perception of stimuli goes "beyond the information given")

The idea Helmholtz proposed in which you achieve constancy through assumed steps that allow you to take one aspect of a visual scene, like distance, into account in judging another aspect, like judging object size.

unconscious intererence

Pathway in parallel processing that connects the occipital lobe and inferotemporal cortex. -aids in identification of visual objects

what system

Pathway in parallel processing that connects the occipital lobe and the posterior parietal cortex. -aids in perception of an object's location

where system

How does the necker cube demonstrate gestalt views on perception?

your perception goes beyond the information given in the drawing by specifying an arrangement in depth (example of a reversible (ambiguous) figure)