AP Psychology Unit 3: Sensation and Perception

Sensory Adaptation

Decreasing responsiveness to stimuli due to constant stimulation

Sensory Habituation

Perception of sensations partially due to how focused someone is on them

Perception

What sensations activate senses + what a person is focused on

The process of understanding and interpreting sensations

Cocktail-Party Phenomenon

Brain focuses attention on a particular stimuli (usually auditory like having your name called in a crowded room)

Sensation

Process of activation of senses, perception: understanding sensations

Light intensity

The color the eye sees depends on this

Cornea

This is a protective covering that helps focus light when it enters the eye

Pupil

This part of the eye is like a camera shutter, and light enters it right after it goes through the cornea

Iris

This part of the eye is muscles that dilate or shrink depending on if there is more or less light

Lens

During the accommodation part of seeing, light is focused by this curved and flexible structure

Retina

Images are projected here, onto the back of the eye. It serves like a screen

Cones

In the eye: first cell layer that is activated by color

Rods

In the eye: first cell layer that is activated by black or white

Fovea

The very center of the retina: highest concentration of cones

Peripheral vision relies on rods and is black and white

Ganglion cells

The next layer of bipolar cells after rods and cones. Activated if enough rods and cones fire

Optic Chiasm

Where the parts of the optic nerve cross

Blind Spot

Where the optic nerve leaves the retina (no rods or cones there)

Trichromatic Theory

A theory of color vision:

(Oldest, simplest): 3 types of cones in the retina (blue, red, green) → activated in different combinations

• Cannot explain afterimages (white / blank space shows opposite of previous color), and color blindness

Dichromatic

This type of color blindness can’t see red/green or blue/yellow shades

Monochromatic

This type of color blindness can only see in shades of gray

Opponent-Process Theory

A theory of color vision:

Sensory receptors in retina come in red/green, blue/yellow, black/white (pairs)

• If one sensor is stimulated → the other is inhibited from firing

• Afterimages: if look at red: fatigue the real sensors → Switch gaze and the opposing ones fire with afterimage

  • Color blindness: if color sensors do not come in pairs or missing one pair

Amplitude

Height of a sound wave. Th

Frequency

The length of sound waves. Determines pitch of a sound (megahertz

Cochlea

The fluid inside this structure is lined with a basilar membrane, and hair cells inside are connected to the organ of corti

Place theory

A pitch theory:

Hair cells in the cochlea respond to different frequencies based on where they are located (some respond to high, some respond to low) and they move in different places

• Accurately describes upper, but not lower pitches

Frequency theory

A type of pitch theory:

 Lower tones are sensed by the rate at which cells fire → different firing rates = different frequencies

Conduction Deafness

This type of deafness is when there is something wrong when conducting sound to the cochlea

Nerve / Sensorineural Deafness

This type of deafness is when Hair cells in the cochlea are damaged (usually by loud noise)

• Hair cells do not regenerate → much more difficult to treat

Touch

This sense is activated when skin is indented or pierced and nerve endings respond to pressure or temperature

Gate control theory

A theory that states that some pain messages have higher priority than others

• A “gate” opens for higher priority but stays closed for lower priority pain, meaning that it is into felt

  • Endorphins swing the gate open/shut and control the amount of pain someone feels

Papillae

Bumps on one’s tongue, inside of cheeks, and the roof of the mouth that hold taste buds, which absorb taste (chemicals)

Olfactory bulb

This part in the smell / olfaction pathway gathers messages from the olfactory receptor cells and sends information to the brain

Vestibular Sense

This body position sense tells one how the body is positioned in space

• 3 semicircular canals in the inner ear give the brain feedback about body orientation (tubes with fluid)

• When the position of the head changes, the fluid moves, causing the sensors to move and the hair cells activate the neurons to the brain

  • Nausea + Dizziness: When the liquid becomes agitated from too much movement

Kinesthetic Sense

This body position sense gives feedback on the position and orientation of specific body parts

• Receptors in muscles and joints send information to the brain about limbs 

• Visual feedback helps also to keep track of the body

  • Provides feedback on where your body parts are in relation to other ones

Absolute threshold

 Smallest amount of stimulus a person can detect 50% of the time

• Stimuli below this are called subliminal

Subliminal

Stimuli below the absolute threshold

Difference threshold

How much a stimulus needs to change before a difference is noticed

• Just-Noticeable Difference: Smallest amount of needed change

Just-Noticeable Difference

The smallest amount of needed change to notice a difference

Weber’s Law

 change needed is proportional to the original intensity of stimulus

• More stimulus = more change is required to be noticed

  • Each sense varies by a constant (ie hearing is 5% (100 decibels need to change to 105 to be noticed. 8% for vision)

Signal Detection Theory

A perceptual theory that states the following:

Effects of distractions and interference experienced when perceiving the world

• Tries to predict what will be perceived when stimuli are competing → predict perceptual mistakes

• False Positive: Think we perceive a stimulus that isn’t there (ex: think friend is there but it’s actually a stranger)

• False Negative: Not perceiving a present stimulus (ex: not reading directions on a test)

False Positive

False perception of an absent stimulus

False negative

Not perceiving a present stimulus

Top-Down Processing

This perceptual theory states the following:

Perceive by filling in gaps in what is sensed (like looking at clouds)

• Experiences create schemata: mental representations on how we expect the world to be

• Can create a perceptual set: predisposition to perceiving something in a certain way

• * Use background knowledge (schemata) to perceive the missing information

• Parent groups in the 1970s were concerned about backmasking: hidden messages in music played backwards

  • Expected to hear threatening message (schemata of evil music) which led them to hear false messages

Schemata

mental representations on how we expect the world to be

Perceptual Set

• predisposition to perceiving something in a certain way

Bottom-Up Processing / Feature Analysis

This perceptual theory states the following

Using only features of the object itself to build a complete perception

• Start at the bottom with individual characteristics and put together into a final perception

• Hard to imagine because it’s an automatic process

• Feature detectors in the visual cortex perceive basic features (ines, curves, motion)

  • Mind builds a picture from bottom → up

  • Longer but more accurate

Gestalt Rules

Principles that govern how people perceive groups of objects

• Normally, images are perceived as groups instead of individual elements

• Proximity: Objects close together -- likely a group

• Similarity: : Objects similar in appearance -- likely a group

• Continuity: Objects in a particular line or curve (trail or figure) -- group

Closure: Similar to top-down processing (objects making a recognizable image)

Constancy

Ability to maintain a constant perception of an object despite changing angle or light

Size Constancy

 objects closer to the eyes create a bigger image in the retina, however the human mind takes instance into account when estimating size

Shape Constancy

 Objects from different angles look as if they are different shape. Mind knows that the shape is constant (depending on familiarity)

Brightness Constancy

 Perceive objects as constant color even if the light and reflection changes

Depth Cues

These help humans perceive the world in three dimnsions

Stroboscopic Effect

 Movies and flipbooks → still images changing at a certain speed appear to be moving

Phi Phenomenon

Holiday lights: series of lights turned on / off at a particular rate make it seem as if they are a moving singular light

Autokinetic Effect

Spot of light projected in dark room → appears to move

Visual Cliff Experiment

An experiment by Eleanor Gibson

 Do human infants perceive depth? 

• Constructed a “cliff” covered with glass

  • Infant does not go off the visual cliff → meaning it can perceive depth (at 3 months old)

Monocular Cues

These depth cues do not rely on someone having two eyes

Binocular Cues

Depth Cues that rely on someone aving two eyes

Convergence

• As an object gets closure to the face, eyes move toward each other to keep focus 

  • The more the eyes converge, the closer the object is

Extrasensory Perception / ESD

Claiming to perceive a sensation “outside” of normal senses

• Psychologists are skeptical because no reliable evidence outside our 5 senses

• Usually it’s explained by deception, magic tricks, or coincidence