Sensation and Perception

Sensation

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

Perception

The process by which our brain organizes and interprets sensory information, enabling us to recognize objects and events and meaningful.

Absolute thresholds

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

Difference threshold

Minimum stimulus difference a person can detect half the time.

Just-noticeable difference

The minimum amount of change in a physical stimulus required for a subject to detect reliably a difference in the level stimulation.

Weber’s Law

The principle that, to be perceived as difference, two stimuli must differ by a constant minimum percentage (rather than a constant amount). Two lights, for example, must be different in intensity by 8%.

Sensory adaptation

Diminished sensitivity as a consequence of constant stimulation. Ex: you may not notice a fan’s noise until its turned off.

Synesthesia

A phenomenon that causes sensory crossovers, such as tasting colors of feeling sounds.

Transduction

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

Cornea

THe eye’s clear, protective outer layer, covering the pupil and iris. Light enters here, and the cornea bends light to provide focus.

Iris

Ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening. Dilates or constricts in response to light intensity.

Pupil

Adjustable opening in the center of the eye through which light enters.

Lens

Transparent structure behind the pupil that changes shape to help focus images on the retina. Light hits it after passing through the pupil. Lens focuses light rays into an image on the retina.

Retina

Light-sensitive back inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual info.

Optic Nerve

Nerve that carries neural impulses from the eye to the brain.

Accomidation

Eye’s lens changes shape to focus images of near or far objects on the retina.

Rods

Retinal receptors that detect black, white, grey. Sensitive to movement; necessary for peripheral and twilight vision, when cones don’t respond.

Cones

Retinal receptors concentrated near the center of the retina and that function in day light or in well-lit conditions. Detect fine detail and give rise to other color sensations. 3 types of cones.

Blind spot

Area with no light-sensitive cells

Fovea

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

Ganglion cells

Have axons that twine together like strands of a rope to form the optic nerve. Neurons in retina and send visual info to brain.

Bipolar cells

Neurons in the retina that transmit visual info from photoreceptors to ganglion cells.

Visual transduction

1. Light hits the cornea.

2. gets refracted to the pupil

3. travels through the pupil to the lens

4. refracted/focused to the fovea

Nearsightedness (myopia)

If lens focuses the image on a point in front of the retina, you can see near objects clearly but not distant objects.

Farsightedness

Seeing distant objects better than near objects-occurs when the lens focuses the image on a point behind the retina.

Young-Helmholtz Theory (three color theory)

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

Opponent process theory

The theory that opposing retinal process (red-green, blue-yellow, white-black) enable color vision. For ex, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.

After-image

Visual illusion in which retinal impressions persist after the removal of a stimulus.

wavelength

The length of a wave from one peak to the next

Intensity

The strength or force of a stimulus, related to perceived brightness

Amplitude

The magnitude or strength of a reaction or of a stimulus.

Dichromatism

When only two cone types are functional

Monochromatism

When none or only one type of cone receptor is functional

Prosopagnosia

Face blindness; damaged brain visual cortex

Frequency

The number of complete wavelengths that pass a point in a given time.

Amplitude (sound waves)

Determines intensity, the brightness we perceive.

Pinna

Collects sound waves and channels them into the ear canal

Ear canal

Transports sound from outer ear to eardrum and protects itself

Middle ear

Concentrate the vibrations of the eardrum on the cochlea’s oval window

Eardrum

Seperates the outer ear from middle ear. When sound waves hit the eardrum it vibrates, then is transferred to tiny bones in the middle ear.

Ossicles (Hammer/Anvil/Stirrup or Malleus/Incus/Stapes)

Transfer and amplify air vibrations into the inner ear to be processed as sound

Oval Window

Transmits sound to the hair cells

Cochlea

Sound waves traveling through the cochlear fluid trigger nerve impulses.

Semicircular Canals

Help keep our balance, has fluid in it.

Auditory transduction

1. starts by converting sound pressure waves into vibrations of the eardrum and ossicles.

2. the vibrations get transmitted through the middle ear to the cochlea

3. vibrations converted into electrical signals by the hair follicles.

Sensorineural deafness

Caused by damage to the cochlea’s receptor cells or to the auditory nerve. Treated with hearing aid or cochlear implants.

Conductive deafness

Caused by damage to the mechanical system that conducts sound waves to the cochlea. Treated with a hearing aid

High amplitude impacting hearing

The louder the noise, the more quickly it can damage your hearing and can lead to hearing loss.

Place theory

Theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated. Presumes we hear different pitches because different sound waves trigger activity at different places along the basilar membrane.

Frequency theory

The rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch.

Volley principle

When high frequency sounds are experienced too frequently for a single neuron to adequately process and fire for each sound event, the organs of the ear combine multiple stimuli into a “volley”.

How do smell and taste interact

Information from taste buds travels to an area between the brain’s frontal and temporal lobes. It registers in an area not too far from where the brain receives information from our sense of smell, which interacts with taste.

Four basic touch sensations

Pressure, warmth, cold, pain

Touch

Pressure is detected by sensory receptors; sensory information is then sent from the skin to the spinal cord, then the thalamus, then the brain.

Gate-control theory

The theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain. The “gate” is opened by activity of pain signals traveling up small nerve fibers and closed by activity in large fibers or by information coming from the brain.

Phantom limb sensation

The brain creates pain. When it lacks the normal sensory input from a missing limb, the brain may interpret and amplify spontaneous but irrelevant central nervous system activity.

Vestibular sense

Our balance sense; our sense of body movement and position that enables our sense of balance.

Kinesthetic senses

Our movement sense- our system for sensing the position and movement of individual body parts

Bottom-up processing

Information processing that begins with the sensory receptors and works up to the brain’s integration of sensory information. Enables sensory systems to detect lines, angles, colors that form images.

Top-down processing

Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations. You interpret what your senses detect.

Perceptual Set

A mental pre disposition to perceive one thing and not another.

Gestalt psychology

It focuses on how people perceive objects, shapes, and forms as wholes rather than separate parts.

Figure-ground

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

Proximity

If there’s an image of six lines, but you see three sets of 2 lines.

Similarity

If you see circles of black and white, but they are perceived as two groups, color and no color

Selective attention

Focusing conscious awareness on a particular stimulus.

Cocktail party effect

Your ability to attend to only one voice within a room of many as you talk with a party guest.

Inattentional blindness

Failing to see visible objects when our attention is directed elsewhere.

Visual cliff experiment

A laboratory device for testing depth perception in infants and young animals.

Binocular cues

A depth cue, that depends on the use of two eyes

Retinal disparty

A type of binocular cue. By comparing retinal images from two eyes. the brain computes distance the greater the difference between the two images, the closer the object.

Convergence

A type of binocular cue. A cue to nearby objects’ distance, enabled by the brain combining retinal images.

Relative clarity

Monocular cue in which closer objects appear more clearly than distant ones.

Relative size

When a further person appears smaller than a person who stands closer.

Texture gradient

Monocular cue when you see texture of something up close but not far away.

Interposition

Monocular cue, when one thing blocks the object behind it, it seems closer than the object that’s blocked.

Linear perspective

Monocular cue, Parallel lines appear to meet in the distance as you get closer.

Perceptual constancies

Perceiving objects as unchanging even as illumination and retinal images change.

Perceptual adaptation

The ability to adjust to changed sensory input, including an artificially displaced or even inverted visual field. It helps us guide and maintain brain pathways that enable our perception.