AP Psychology - Unit 4: Section 2

Wavelength

The distance from the peak of one light or sound wave to the peak of the next

Electromagnetic wavelengths vary from short blips of gamma rays to the long pulses of radio transmission

Short wavelength = High frequency (bluish colors), Long wavelength = Low frequency (reddish colors)

Amplitude

The height from peak to trough of a wave

Influences the brightness of colors: Large amplitude = Bright colors, Small amplitude = Dull colors

Cornea

The eye’s clear, protective outer layer that covers the pupil and iris

Pupil

The adjustable opening in the center of the eye through which light enters

Iris

A ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening

Lens

The transparent structure behind the pupil that changes shape to help focus images on the retina

Retina

The light-sensitive inner surface of the eye, containing the receptor rods and cones, as well as layers of neurons that begin the processing of visual information

Accommodation

The process by which the eye’s lens changes shape to focus near or far objects on the retina

Photoreceptors

Specialized cells in the retina of the eye that convert light into electrical signals, which are then transmitted to the brain for visual perception

The rods and cones of the retina

Rods

Retinal photoreceptors that detect black, white, and gray, and are sensitive to movement

Necessary for peripheral and twilight vision, as they are the primary photoreceptors for dim light

Cones

Retinal photoreceptors that are concentrated near the center of the retina and function in daylight or in well-lit conditions, as well as they detect fine detail and create color sensations

Optic nerve

The nerve that carries the neural impulses from the eye to the brain

AKA the “Visual nerve”

Bipolar cells

Cells that are activated by the chemical reaction of light energy triggering chemical changes and sparking neural signals

They then activate neighboring ganglion cells

Ganglion cells

Cells whose axons twine (thread) together like the strands of a rope to form the optic nerve

Fovea

The central focal point in the retina, around which the eye’s cones cluster

Functions in visual acuity (sharpness and focus)

Blind spot

The point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there

Young-Helmholtz trichromatic (three-color) theory

The theory that the retina contains three different types of color receptors (cones)—one most sensitive to red, one most sensitive to green, and one to blue—which, when stimulated in combination, can produce the perception of any color

Black and white are produced by the rods

Monochromatism (monochromatic vision)

The complete color-blindness in which all colors appear as shades of one color

Dichromatism (dichromatic vision)

The color-blindness in which only two of the three primary colors can be discerned

The type of color-blindness that cannot distinguish the difference between red and green

Afterimage

A visual illusion that occurs when an image continues to appear in your vision after the original stimulus is gone

Two types: 

• Positive afterimage: Have the same colors as the original image and fade quickly

• Negative afterimage: Have the complementary colors to the original image

Related to the Opponent-Process theory

Opponent-process theory

The theory that cone photoreceptors are paired together (red-green, blue-yellow, white-black); The theory that opposing retinal processes (red-green, blue-yellow, white-black) enable color vision

This theory focuses on how the brain perceives rather than how eye collects information

Activation of one color of the pair inhibits the activation of the other

Ex. Negative afterimage: Staring at green tires your green response. So when you stare at a white area after tiring your green response, only the red part of the red-green pairing is fired normally.

Feature detectors

Nerve cells in the brain’s visual cortex of the occipital lobe that respond to specific features of the stimulus (shape, angle, movement)

They receive information from individual ganglion cells in the retina and pass it to other cortical areas, where supercell clusters respond to more complex patterns

Parallel processing

Processing many aspects of a problem simultaneously

The brain’s natural mode of information processing for many functions, including vision

The brain delegates the work of processing motion, form, depth, and color to different areas

Frequency

The number of wave cycles (oscillations) that pass a fixed point in a given amount of time, typically measured in Hertz (Hz) which represents cycles per second

Gestalt

An organized whole

Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes

You might see more than what is actually there

As we look straight ahead, we cannot separate the perceived scene into our left and right fields of view; Our conscious perception is, at every moment, a seamless scene (an integrated whole)

Figure-ground

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

Making the distinction between a figure and the ground (surroundings)

Visual cliff

A laboratory device for testing depth perception in infants and young animals

A model of a cliff with a “drop-off” area that was actually covered by sturdy glass. Mothers tried to coax their offspring to crawl out onto the glass, but most refused to do so, indicating that they could perceive depth.

Binocular depth cues

A depth cue that depends on the use of two eyes

Used to judge the distance of nearby objects

2 types: Convergence and retinal disparity

Retinal disparity

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

A type of binocular depth cue

Grouping

The perceptual tendency to organize stimuli into coherent groups based on proximity, continuity (patterns), and closure

Convergence

The inward angle of the eyes focusing on a near object

A type of binocular depth cue

Monocular depth cues

A depth cue available to either eye separately

Types: Relative height, light and shadow, Relative size, interposition, and linear perspective

Interposition

Relies on an object partially blocking another object to determine which is closer

A type of monocular depth cue

Linear perspective

A depth perception clue that can be seen with just one eye; Occurs because parallel lines appear to converge (get closer together) as they recede into the distance, creating a sense of depth and distance

Ex. The edges of a road appear to get closer and closer together, converging to a single “vanishing point” as they extend into the distance in the horizon

A type of monocular depth cue

Perceptual constancy

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

A top-down process that recognizes objects without being deceived by changes in color, brightness, shape, or size

Perceptual adaptation

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

Proximity

A law that states that we group nearby figures together

A Gestalt law of grouping

Continuity

A law that states we perceive smooth, continuous patterns rather than discontinuous ones

A Gestalt law of grouping

Closure

A law that states we fill in gaps to create a complete, whole object

A Gestalt law of grouping

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

Ex. Visual cliff

Relative height

We perceive objects that are higher in our field of vision to be farther away than those that are lower; Lower = closer, Higher = farther

A type of monocular depth cue

Light and shadow

Nearby objects reflect more light into our eyes than more distant objects

Given two identical objects, the dimmer one appears to be farther away

A type of monocular depth cue

Relative size

If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away

A type of monocular depth cue

Stroboscopic movement

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

Ex. Cartoons, flipbooks

Phi phenomenon

To perceive two adjacent stationary lights blinking on and off in quick succession as one single light moving back and forth

Color constancy

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

Brightness constancy

Perceiving an object as having constant brightness even as its illumination varies

This perception of constancy depends on relative luminance (the amount of light an object reflects to its relative surroundings

Shape constancy

Perceiving an object as having an unchanging shape, even while our distance from it varies

Size constancy

Perceiving an object as having an unchanging size, even while our distance from it varies

Ex. We assume a car is large enough to carry people, even when we see its tiny image from two blocks away

Nearsightedness

A vision condition where distant objects appear blurry because the eyeball is too long or the cornea is too curved, causing light to focus in front of the retina instead of on it

Farsightedness

A vision condition where distant objects can be seen clearly, but near objects appear blurry because the eyeball is too short or the cornea is less curved, causing the light rays for near objects are focused behind the retina instead of on it

Prosopagnosia

A neurological disorder characterized by the inability to recognize familiar faces; An inability to recognize faces, despite having healthy vision, memory, and intelligence

For someone with prosopagnosia, seeing a person is a sensory experience without the perception of recognition, which can be caused by damage to the visual association cortex

AKA “face blindness”

Autokinetic effect

A visual illusion where a stationary point of light in a dark room appears to move

Occurs because the brain has no reference point and the eye’s tiny, involuntary movements (saccades) make the light seem to drift