AP Psych Sensation and Perception

Sensation

your “window” to the world; taking in information

Perception

interpreting what comes in your “window”; interpreting/understanding information taken in

Vision

• Visual Information Processing

• Color Vision

Hearing

• The Stimulus Input: Sound Waves

• The Ear

• Hearing Loss and Deaf Culture

Bottom-up

• Begins with sense receptors and works UP to the brain

• Associated with Sensation

• Can be thought of as “first” of the two

Top-down

• Information processing guided by “higher level” mental processes

• Associated with Perception

• Can be thought of as “second” of the two

Absolute Threshold

Minimum stimulation needed to detect a particular stimulus 50% of the time.

Difference Threshold

Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND).

Weber’s Law

• Computes the "Just Noticeable Difference".

• The change needed is proportional to the original intensity of the stimulus

• Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Weber fraction: k = δI/I.

• Light constant is 8% difference, weight 2%, and tone is 3%

Subliminal Messages

Stimuli below our absolute threshold.

Signal Detection Theory

• Predicts how and when we detect the presence of a stimulus

• Assumes that “absolute threshold” is dependent on context/situation

Sensory Adaptation

Diminished sensitivity as a consequence of constant stimulation.

Selective Attention

• focus 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 a visual change when our attention is directed elsewhere

Perceptual Set

• Set of mental tendencies and assumptions

• Affects what we see

Context Effect

A given stimulus may trigger radically different perceptions, partly because of different schemas, but also because of immediate context.

Visual capture

When vision competes with our other senses, vision usually wins

Gestalt Psychology

• emphasizes our tendency to integrate pieces of information into meaningful wholes

• Whole is greater than sum of parts

Form Perception (figure ground)

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

Proximity 

group objects that are close together as being part of same group

Similarity

objects similar in appearance

Continuity

objects that form a continuous form

Connectedness

objects that are uniform and linked are perceived as single units

Closure

we fill gaps to create a whole or complete image

Depth Perception

____ _____ enables us to judge distances. Gibson and Walk  (1960) suggested that human infants (crawling age) have depth perception. Even newborn animals show depth perception.

Binocular Cues

• Two eyes! Inches apart…

• Retinal Disparity - as an object comes closer to us, the differences in the images for our eyes becomes greater.

  • “finger sausage”

  • 3-D movies

• Convergence  - as an object comes closer, our eyes have to come together

Retinal Disparity

• as an object comes closer to us, the differences in the images for our eyes becomes greater.

  • “finger sausage”

  • 3-D movies

Convergence

as an object comes closer, our eyes have to come together

Monocular Cues

• You really only need one eye to use these.

  • Linear Perspective

  • Interposition

  • Relative Size

  • Texture Gradient

  • Light / Shadowing

Interposition

Objects that occlude (block) other objects tend to be perceived as closer.

Relative Clarity

Because light from distant objects passes through more light than closer objects, we perceive hazy objects to be farther away than those objects that appear sharp and clear.

Texture Gradient

Indistinct (fine) texture signals an increasing distance.

Relative Height

We perceive objects that are higher in our field of vision to be farther away than those that are lower.

Relative motion

Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction.

Linear Perspective

Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance.

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.

Motion Perception

Objects traveling towards us grow in size and those moving away shrink in size. The same is true when the observer moves to or from an object.

Phi Phenomenon

When lights flash at a certain speed they tend to present illusions of motion. Neon signs use this principle to create motion perception.

Stroboscopic Effect

a rapid series of slightly varying images perceived as moving images (flip book, “old” movies)

Autokinetic effect

illusion of movement of a still spotof light in a dark room

Perceptual Constancy

Perceiving objects as unchanging even as illumination and retinal images change. Perceptual constancies include constancies of shape and size.

Sensory Transduction

• Transforming stimulus energy into neural impulses

• Senses to thalamus, then to various brain parts

Pupil

adjustable opening in the center of the eye

Iris

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

Lens

transparent structure behind pupil that changes shape through accommodation to focus images on the retina

• Accommodation

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

Retina

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

Optic nerve

nerve that carries neural impulses from the eye to the brain

Blind Spot

point at which the optic nerve leaves the eye, creating a “blind spot”

Fovea

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

• Rods

peripheral retina 

• detect black, white and gray

• twilight or low light

Cones

• near center of retina 

• fine detail and color vision

• daylight or well-lit conditions

Color-Deficient Vision

• People who suffer red-green blindness have trouble perceiving the number within the design

• They lack functioning red- or green- sensitive cones, or sometimes both

Opponent-Process Theory

opposing retinal processes enable color vision

Color  Processing

_____ ____ occurs in two stages:  (1) the retina’s red, green, and blue cones respond in varying degrees to different color stimuli, as the trichromatic theory suggests, (2) then their signals are processed by the nervous system’s opponent-process cells, en route to the visual cortex.

Parallel Processing

The processing of several aspects of an object simultaneously, like colors, motion, form, and depth

Audition

the sense of hearing

Frequency

the number of complete wavelengths that pass a point in a given time

Pitch

• a tone’s highness or lowness

• depends on frequency

• Long waves have low frequency and low pitch 

• Short waves high frequency and high pitch

The cochlea vibrates.

• coiled, bony, fluid-filled tube in the inner ear where hair cells are located through which sound waves trigger nerve impulses 

• Cochlea is lined with mucus called basilar membrane

Place Theory

• Different pitches stimulate different parts of the cochlea’s basilar membrane 

• Best explains high pitch

Frequency Theory

• All hairs vibrate but at different speeds

• the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone

• Best explains low pitch

Conduction Deafness

• Something goes wrong with the mechanical/vibration process in hearing.

• Hearing aids to help.

Nerve (Sensorineural) Deafness

• The hair cells in the cochlea get damaged.

• Loud noises can cause this type of deafness.

• NO WAY to replace the hairs.

• Cochlear implant is possible.

“Gate-Control Theory” of Pain

• spinal cord blocks or allows pains signals to pass to brain

• small nerve fibers “open” the gate

• large nerve fibers “close” the ga

Sensory Interaction

principle that one sense influences others

Kinesthetic Sense

• tells us where our body parts are

• uses receptors located in our muscles, joints, and tendons

• sense of our body parts’ position and movement

Vestibular Sense

• tells us where our body is oriented in space.

• our sense of balance.

• located in our semicircular canals and vestibular sacs of the inner ear.