Chapter 4: Sensation and perception

sensation

The process by which our sensory organs receive stimulus energies from the environment and transduce them into the electrical energy of the nervous system

transduction

The transformation of sensory stimulus energy from the environment into neural impulses

perception

The neural processing of electrical signals to form an internal mental representation inside your brain of what’s on the outside

psychophysics

The study of the relationship between the physical characteristics of environmental stimuli and our mental experience of them

absolute threshold

the minimum amount of stimulation necessary for someone to detect a stimulus half of the time

signal detection theory

An approach to measuring thresholds that takes into account both the intensity of the stimulus and psychological biases for a more accurate assessment

Difference threshold

the minimum difference required between two stimuli for an observer to detect a difference half the time

Weber’s law

The observation that the likelihood of perceiving a stimulus change is proportional to the magnitude of the stimulus

Adaptation

A phenomenon whereby an individual stops noticing a stimulus that remains constant over time, resulting in enhanced detection of stimulus changes

wavelength

• The distance between any two consecutive crests or troughs of a wave

1. Variations determine the quantity/hue/color we perceive

frequency

• The number of cycles per second of a wave

1. Relates to wavelength

2. Higher frequencies = shorter wavelength

amplitude

• The height of the crests of a wave

1. Variations determine the quantity/intensity/brightness of color

cornea

The transparent covering at the front of the eye

pupil

A hole in the iris where light enters the eye

iris

• The colored muscle circling the pupil

1. The iris can increase or decrease the size of the pupil to adjust how much light enters the eye.

lens

A membrane at the front of the eye that focuses the incoming light on the retina

accommodation

Adjustments of the lens’ thickness by specialized muscles to change the degree to which it bends

retina

A surface on the back of the eye that contains the photoreceptor cells, which contain photopigments that are sensitive to light

rod

A Photoreceptor cell that primarily supports nighttime vision

cone

A Photoreceptor cell that is responsible for high-resolution color vision

optic nerve

A bundle of axons that converge from the retina and transmit action potentials to the brain

blind spot

An area in the middle of the visual field where there are no photoreceptors and no information can be received

Myopia

Nearsightedness; involves faraway objects being projected too far in front of the fovea

hyperopia

Farsightedness; involves a near object overshooting the back of the eye, behind the fovea

Fovea

• A small pit in the center of the retina that is densely packed with cones

1. When seeing in daytime light, our eyes move to focus stimuli onto the fovea, which brings them into focus.

2. Most rods are in the rental periphery

trichromatic theory

A theory of color perception stating that three types of cone cells, each most sensitive to a specific wavelength of light, work together to produce our perception of a multicolored world

Opponent-process theory

• A theory of color perception stating that information from the cones is separated into three sets of opposing or opponent channels in the ganglion cell layer

• Colors on opposite sides of the color wheel are perceived as opposites 

1. Red/green

2. blue/yellow

3. black/white

featured detectors

specialized cells in the visual cortex that respond to basic features such as lines, edges, and angles

visual association cortex

The regions of the brain where objects are reconstructed from prior knowledge and information collected by the feature detectors

prosopagnosia

A visual disorder in which individuals are unable to recognize the identity of faces

phi phenomenon

A visual illusion in which the flashing of separate images in rapid succession is perceived as fluid movement

pitch

The perceptual quality of sound that makes a flute sound high and a tuba sound low

Outer ear (pinna)

designed to capture and funnel sound waves through the ear canal to the middle ear

Middle ear

• The portion of the ear containing the eardrum and ossicles 

 The eardrum, called the tympanic membrane, responds to sound waves by moving in and out with corresponding vibrational pressure changes

ossicles

Three tiny bones in the ear - the hammer, anvil, and stapes - that act as levers to amplify incoming sound waves

inner ear

The innermost part of the ear, where the cochlea resides

cochlea

A spiral structure in the inner ear where the basilar membrane, which contains auditory sensory neurons, is located

basilar membrane

A structure in the cochlea where the auditory cilia, auditory sensory neurons (hair cells), are located

oval window

Amplified sound waves are delivered to the cochlea by the ossicles through a membrane

frequency theory

• A theory of pitch perception stating that the brain uses the frequency of auditory sensory neuron firing to indicate pitch

1. Best explains the perception of low-pitched sounds

place theory

• A theory of pitch perception stating that different pitches arise from stimulation at different places along the basilar membrane

1. Best explains the perception of high-pitched sounds

primary auditory cortex

The region of the brain, located in the temporal lobe, where sound is processed

tonotopic organization

The arrangement of the auditory system such that nearby frequencies are processed near each other in the brain, resulting in a sound map