Sensation & Perception | AP Psychology

What is the difference between sensation and perception

Sensation is the receiving of stimuli from the outside environment whereas perception is the organizing and interpreting of sensory information.

Absolute threshold

The minimum stimulation needed to detect a particular stimulus 50% of the time

Example: You are letting your sister cut your shirt a shorter length. She cuts so little that you don't even notice a change. She needed to cut at least 2 inches for you to notice that the shirt looks different.

Difference threshold

the minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as a just noticeable difference (or jnd).

Weber's Law

the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount).

Sensory Adaptation

diminished sensitivity as a consequence of constant stimulation

(When we are constantly exposed to a stimulus that does not change, we become less aware of it because our nerve cells fire less frequently)

Why is sensory adaptation useful?

We get the freedom to focus on informative changes in our environment without being distracted by background chatter

Ex: Stinky or heavily perfumed classmates won't smell themselves "because they adapt to what's constant and detect only change" (We perceive the world not exactly as it is, but as it is useful for us to perceive it.)

What does sensory adaptation have to do with the movements of the eye?

Our eyes are always moving. This continual flitting from one spot to another ensures that stimulation on the eyes' receptors continually changes

Visual Stimulation

Our eyes receive light energy and transduce it into neural messages that our brain then processes into what we consciously see

Stimulus Input

When looking at a color, let's say red for example, what strikes your eyes is not the particles of the color red but pulses of electromagnetic energy that your visual system perceives as red. What we see as visible light is but a thin slice of the whole spectrum of electromagnetic energy, ranging from imperceptibly short gamma rays to the long waves of radio transmission.

Rods

Retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond

Cones

Retinal receptor cells that are connected near the center of the retina and that function in daylight or in well-light conditions. The cones detect fine detail and give rise to color sensations

Bipolar Cells

specialized cells which connect rods and cones to the ganglion cells of the optic nerve

Ganglion Cells

the specialized cells which lie behind the bipolar cells whose axons form the optic nerve which takes the information to the brain

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 Theory

the theory that the retina contains three different color receptors—one most sensitive to red one to green one to blue—which when stimulated in combination can produce the perception of any color.

Opponent-Process Theory

the theory that opposing retinal processes (red-green yellow-blue white-black) enable color vision. For example some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.

Afterimage

Sensations that linger after the stimulus is removed. Most visual afterimages are negative afterimages, which appear in reversed colors.

Color Constancy

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

How the process of perception is affected by selective attention

In a process traditionally known as sensation, our senses of vision, hearing, taste, smell, and touch detect physical energy from the environment and encode it as neural signals. Aided by knowledge and expectations, our brain perceives meaning in these signals. We selectively attend to, and process, a limited number of the data bombarding our senses and block out the others. This focused attention can result in inattentional or change blindness, and even choice blindness.

Figure-Ground Relationship

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

Proximity Grouping

We group nearby figures together. We see not six separate lines, but three sets of two lines

Continuity Grouping

We perceive smooth, continuous patterns rather than discontinuous ones.

Closure Grouping

We fill in gaps to create a complete, whole object. Such principles usually help us construct reality.

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.

Monocular cues

depth cues, such as interposition and linear perspective, available to either eye alone

Binocular cues

depth cues, such as retinal disparity, that depend on the use of two eyes

Visual cliff

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

Perceptual constancy

perceiving objects as unchanging (having consistent shapes, size, brightness, and color) even as illumination and retinal images change

Size constancy

We perceive objects as having constant size, even while our distance from them varies. (Seeing a tiny image of a car far away, but still knowing that it's big enough to carry people).

Shape constancy

We perceive the form of familiar objects as constant even while our retinas receive changing images of them. Our brain manages this feat thanks to visual cortex neurons that rapidly learn to associate different views of an object.

Color constancy

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

How does the perceived distance-size relationship operate in visual illusions?

There is a close relationship between perceived size and perceived distance. Knowing an object's size gives us clues to its distance knowing its distance gives clues about its size. This interplay sometimes misleads us, as when we misread monocular distance cues and reach the wrong conclusions, as in the Moon, Ponzo, and Muller-Lyer illusions

Understand the debate over the role of nature and nurture in perception, and what research findings on sensory deprivation and restored vision have contributed to this debate.

If all aspects of visual perception were entirely inborn, people who were born blind but regained sight after surgery should have normal visual perception. They do not. After cataract surgery, for example, adults who had been blind from birth are able to distinguish figure from ground and to perceive colors, but they lack the experience to recognized shapes, forms, and complete faces. Further evidence comes from animals reared with severely restricted visual input, who suffered enduring visual handicaps when their visual exposure was returned to normal. Clinical and experimental evidence indicated that there is a critical period for some aspects of sensory and perceptual development. Without the stimulation provided by early visual experiences, the brain's neural organization does not develop normally.

What does the use of distorting goggles tell us about the adaptability of perception?

When people are given glasses that shift the world slightly to the left or right, or even turn it upside down, they are initially disoriented, but they manage to adapt to their new context and, with practice, to move about with ease. This research demonstrates our ability to adjust to an artificially altered visual field and coordinate our movements in response to that new world.

How does experience, assumptions, expectations, and context affect our perception?

- Our sensory input bounces off our experiences, learned assumptions, and beliefs. Because our learned concepts prime us to organize and interpret ambiguous stimuli in certain ways, our perceptions reflect our version of reality. Thus, some of "see" monsters, faces, and UFOs or "hear" messages that others do not.

- In perceiving a give stimulus that we could interpret by means of several different schemas, we scan the immediate context for information. Connect creates expectations that guide our perceptions. Emotional context can color our interpretation of other people's behaviors- and our own. Perceptual set and context effects interact to help us construct our perceptions.

- Perception is influenced by our experience and sensory input as shown by demonstrations of perceptual set and context effects. ideas stored in memory help us interpret stimuli. our expectations influence our views on ESP

Why are most research psychologists skeptical of claims of ESP?

ESP is one form of purported paranormal phenomena. The three most testable forms of ESP are telepathy, clairvoyance, and precognition. Most research psychologists' skepticism focuses on two points. First, to believe in ESP, you must believe the brain is capable of perceiving without sensory input. Second, parapsychologists have been unable to replicate ESP phenomena under controlled conditions.

Sensation

the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment

Perception

the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

bottom-up processing

analysis that begins with the sensory receptors and works up to the brain's integration of sensory information

top-down processing

information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations

Selective attention

the focusing of conscious awareness on a particular stimulus

Inattentional blindness

failing to see visible objects when our attention is directed elsewhere

Change blindness

failing to notice changes in the environment

Transduction

conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret.

(Stimulus energies to neural impulses)

Examples: - light energy to vision

- Chemical energy to smell and taste

- Sound waves to hearing

- Pressure to touch

Psychophysics

the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them

absolute threshold

the minimum stimulation needed to detect a particular stimulus 50 percent of the time

Signal detection theory

a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes that there is no single absolute threshold and that detection depends partly on a person's experience, expectations, motivation, and alertness.

Subliminal

below one's absolute threshold for conscious awareness

Priming

the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response

Difference Threshold

the minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as just a noticeable difference (or jnd).

Weber's law

the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)

Sensory Adaptation

diminished sensitivity as a consequence of constant stimulation

Perpetual Set

a mental predisposition to perceive one thing and not another

Extrasensory Perception (ESP)

the controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition

parapsychology

the study of paranormal phenomena, including ESP and psychokinesis

Wavelength

the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission

Hue

the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth

Intensity

the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude (height). The higher the wave the more intense the light is

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 plus 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

Optic Nerve

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

Fovea

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

Feature detectors

nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement

parallel processing

the processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving.

Gestalt

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

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

Retinal Disparity

a binocular cue for perceiving depth by comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object.

Phi phenomenon

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

Perceptual adaptation

in vision, the ability to adjust to an artificially displaced or even inverted visual field

Cocktail Party Effect

ability to listen to one voice among many

What energy do we use to see?

Light energy

What happens when you add monochromatic light to color?

It makes them less saturated

How do we perceive color?

- the ways light waves are absorbed and/or reflected by the material around them

- the ways the light waves are absorbed and processed by our eyes

- the ways the information transmitted from our eyes is analyzed by our brains

Visual Capture

the tendency for vision to dominate the other senses

Motion Perception

We perceive motion incredibly well. We judge mostly by the size of the object