Sensation and Perception Part 2

Object Constancy

correctly perceiving objects as constant in their shape, size, color, and lightness, despite raw sensory data that could mislead perception

4 constancies

• size constancy, shape constancy, color constancy, and lightness constancy

Size constancy

correctly perceiving sizes of objects in the world despite changes in retinal-image size created by changes in viewing distance

Shape constancy

correctly perceiving the shape of objects despite changes in retinal image caused by viewing angle

Lightness constancy

correctly perceiving brightness of object whether they are illuminated by dim light or strong sun

Color constancy

correctly perceiving the color of the object in different conditions

How are we able to construct 3-D mental representations from 2-D retinal image?

Binocular Cues and Monocular cues

Binocular Cues

• both eyes

• internal cue for how far away something is

Monocular cues

• each eye alone

• organizational information to infer depth

Retinal (binocular) disparity

each eye receives a different image

• different but overlapping

• use these images to compute distances

Stereoscopic vision (retinal binocular disparity)

ability to perceive depth based on disparities

Convergence (binocular cues)

eye muscles move inward to view close objects

• brain uses this info to infer distance

Texture (monocular cues)

closer items = clearer and sharper textures

Relative size (monocular cues)

if two objects have similar sizes, closer object will be “larger”

Linear perspective (monocular cues)

parallel lines converge as they move away from the perceiver and toward the horizon line

Occlusion (AKA interposition and monocular cues)

overlapping objects block the views of other objects

Motion

another distance and depth cue

Motion parallax

cue in which objects that are closer to us appear to move faster than objects further from us

Tabletop illusion

The role of interpretation in perception becomes clear from misinterpretations, resulting in illusions

Monster illusion

cue to depth makes monster on right appear larger/farther

Ames Box Illusion

first crafted in the 1940s by Albert Ames, a painter turned scientist

• Ames boxes’ rooms play with linear perspective and other distance cues to create size illusions

Ponzo Illusion

The two horizontal lines appear to be different sizes but are actually the same length

Audition

hearing; the sense of sound perception

Sound wave

a pattern of changes in air pressure during a period of time; it produces the percept of a sound

• a sound wave’s amplitude determines loudness; its frequency determines its pitch

• hertz - humans can detect sound waves with frequencies from about 20 Hz to about 20,000 Hz

Hearing pathway

sound waves arrive at the person’s outer ear and travel down the auditory canal to the eardrum

Eardrum

a thin membrane that marks the beginning of the middle ear; sound waves cause it to vibrate

Vestibular Sense

perception of balance determined by receptors in the inner ear

How the vestibular sense is used?

• uses information from receptors in the semicircular canals of the inner ear

• canals contain a liquid that moves when the head moves

• The bending of hair cells at end of canal, generates nerve impulses that inform us of the head’s rotation

Cochlear Implants

• severe hearing problems due to the loss of hair cells in the inner ear

• works by directly stimulating the auditory nerve; does not amplify sound

– When devices are implanted in children who were born deaf, the child’s hearing will be quite functional/normal speech

How do we taste and smell?

Gustation and Olfaction

Gustation

the sense of taste

Olfaction

the sense of smell

What does the gustation and olfaction factors have in common?

• external signals that trigger taste and smell are chemical in nature

• both taste and smell help us decide what to eat

Taste buds

sensory organs in the mouth that contain the receptors for taste

Experience of taste

taste buds send signals to the thalamus > frontal lobe of the brain

Five basic taste

sweet, sour, salty, bitter, and umami (Japanese for “savory” or “yummy”)

Basic process of olfaction

• Odorants pass into the nose and nasal cavity

• contact a thin layer of tissue embedded with smell receptors called the olfactory epithelium

Olfactory epithelium

a thin layer of tissue, within the nasal cavity, that contains the receptors for smell

Olfactory bulb

the brain center for smell, located below the frontal lobes

• Information about whether a smell is pleasant or unpleasant is processed in the brain’s prefrontal cortex.

• The intensity of a smell is processed in brain areas that are also involved in emotion and memory

Haptic sense

the sense of touch

• Touch is perceived through the skin, our largest sense organ

• touch is important for attachment formation

• touch is linked to both pleasure and pain

The skin contains sensory receptors for touch

anything that makes contact with our skin provides tactile stimulation

• for sensing temperature, there appears to be receptors for warmth and receptors for cold

• the integration of various signals and higher-level mental processes produces haptic experiences

Pain receptors exist throughout the body

pain is part of a warning system that stop you from continuing activities that may harm you

Two kinds of nerve fibers have been identified for pain

• fast fibers for sharp, immediate pain; activated by strong physical pressure and temperature extremes

• slow fibers for chronic, dull, steady pain; activated by chemical changes in tissue when skin is damaged