Sensation and Perception (Psych #6)

Sensation

The process by which sensory systems (eyes, ears, and other sensory organs) and the nervous system receive stimuli from our environment and bring it to our brain

Threshold

An edge or a boundary

Absolute Threshold

The minimum amount of stimulation needed to detect a particular stimulus

The absolute threshold is the amt of stimulus that a person can detect ___ % of time

50%

Signal Detection Theory

A theory that predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)

• Developed during the Cold War

Subliminal Stimulus

Stimuli that is below your absolute threshold

Difference Threshold

The minimum amount of different needed to detect that 2 stimuli are not the same

• Also called Just Noticeable Difference (JND)

Weber-Feshner’s Law

States that to perceive stimuli as different, two stimuli must be different by a minimum percentage, rather than by a set amt.

• ex. Weight is 2%

  • 100 lbs → JND needs to be 102+ or 98-

Transduction

Refers to sensory energy being converted/transformed into neural energy

Light

The stimulus that produces vision. Is made up on electromagnetic waves with various wavelengths and amplitudes called a visual spectrum

Wavelength

The distance between two adjacent peaks

Amplitude

The height of a wave

Electromagnetic energy

An energy spectrum that includes many different types of waves. A small portion of this spectrum includes light visible to the human eye.

Hue (Color)

The color of light as determined by the wavelength of the light energy (ROY G BIV)

• The eye can detect 7 million of these.

Amplitude (Color)

The brightness of light as determined by the height of the wave.

Cornea

The clear, curved bulge on the front of the eye that bends light rays to begin focusing them to a central point. Protects the eye.

Pupil

The adjustable opening in the center of the iris, which controls the amount of light entering the eye

In bright conditions…

the iris expands, making the pupil smaller

In dark conditions…

the iris contracts, making the pupil larger

Iris

A ring on muscle tissue that forms the colored portion of the eye and regulates the size of the pupil. A change in size allows more or less light to enter the eye.

Lens

A transparent structure behind the pupil in the eye that changes shape to focus images on the retina. Muscles that change the thickness of the lens, which changes how light is bent, thereby focusing the image.

Accommodation

The lens’ ability to focus on near or far objects on the retina.

Retina

The lights sensitive surface at the back of the eyeball. Contains cells that convert light energy to nerve impulses.

1. Receptor Cells

Specialized cells in every sensory system of the body that can turn other kinds of energy into action potentials (neural impulses) that the brain can process. Present in every sensory to change (transduce) some other form of energy into neural impulses.

Rods

Visual receptor cells located in the retina that can detect only black, white, and grey. Responds to less light than their counterparts, therefore giving us peripheral and night vision.

Rhodopsin

In rods; the photopigment that starts the process of sight.

Cones

Visual receptor cells located in the retina that can detect sharp details and color. Need more light than rods, many clustered in the fovea.

2. Bipolar Cells

Gather information from the rods and cones and pass it onto the ganglion cells. Form the middle layer in the retina

3. Ganglion Cells

Pass information from bipolar cells through their axons. Together, these cells form the optic nerve. Form the top layer of cells in the retina

Fovea

The central focus point of the retina, with a high concentration of cones. Allows us to see clearly, the spot where vision is the most detailed.

Optic Nerve

The nerve that carries visual information form the eye to the occipital lobes of the brain

Blind Spot

Is the point at which the optic nerve travels through the retina to exit the eye; the lack of rods and cones at this point creates a small blind spot.

Acuity

Sharpness and clarity of vision

Myopia

A type of acuity in which focus is in front of the retina

• Only can see near things clearly

Hyperopia

A type of acuity in which focus is behind the retina

• Only can see far things clearly

Glaucoma

Increased pressue on the optic nerve, causing vision loss

Parallel Processing

Our brain processes lots of information simultaneously.

(Color Processing) 1. Trichromatic Theory of Color VIsion

A theory of color vision that says that cones are sensitive to red, green, or blue (RGB) - the three colors that combine to create millions of color combinations.

(Color Processing) 2. Opponent-Process Theory

A theory of color vision that says color is processed by cones organized in opponent pairs (ex. red-green); light that stimulated on half of the pair inhibits the other half.

• Explains the afterimage effect

Dichromats (Color-blindness)

People who lack one of the three types of cones, usually the red-green receptors. Is inherited (via the female), and found more in males.

Monochromats

People who see no color

Sensory Adaptation

Is diminished sensitivity to constant and unchanging stimulation. Id a stimulus is constantly unchanging, eventually a person may fail to respond to it.

Dark Adaptation

a. Pupils enlarge to admit more light into the retina

b. Light sensitive chemicals increase in concentration to be more sensitive to light

Light Adaptation

a. Pupils constrict immediately, reducing the amount of light reaching the retina

b. Light sensitive chemicals fade out, reducing sensitivity to light

Hearing/Audition

Requires sound waves converted into neural energy; done in the ear.

• Ear is structured to capture sound waves in terms of wavelength and amplitude.

Sound

Vibration from the movement of air molecules.

Pitch

A sound’s highness or lowness, which depends on the frequency of the sound wave. Measured in Hertz (Hz)

Hertz (Hz)

A measure of the # of sound waves peaks per second; measures frequency.

• Determines the pitch of sound

Humans’s hearing range (Hz)

20 - 20,000 Hz

Decibel

A measure of the height of the sound wave. Determines the loudness of a sound. Sometimes called amplitude.

Divisions of the Ear

Sound travels through three sections of the ear (Outer, Middle, Inner)

Auditory Canal (Ear Canal)

The opening through which sound waves travel as they move into the ear for processing. Ends at the eardrum.

Tympanic Membrane (Eardrum)

The tissue barrier that transfers sound vibration from the air to the tiny bones of the middle ear.

• Can be damages by objects in the ear or exceptionally loud noises.

Ossicles

Three tiny bones that transfer sound waves from the eardrum to the cochlea

Which is not one of the three bones of the middle ear?

Nail

Oval Window

The point on the surface of the cochlea which receives the sound vibration from the ossicles

• As the oval window vibrates, the fluid in the cochlea vibrates

Semicircular Canals

Parts in the inner ear used in sensing body orientation and balance.

• Relies on fluids in the canals spinning in circles

Veritgo

A disturbance of the fluids in the semicircular canals, causing a sensation of being dizzy and unbalanced

Cochlea

The major organ of hearing; a snail-shaped, bony, fluid-filled structure in the inner ear where sound waves are changed into neural impulses.

Hair cells

The receptor cells for hearing; these are located in the cochlea and are responsible for changing sound vibrations into neural impulses.

• Similar to rods and cones within the eye

Basilar Membrane

Thin strip of membrane within the cochlea that contains the hair cells.

Auditory Nerve

The nerve that carries sound information from the ears to the temporal lobes of the brain.

Conductive Hearing Loss

Hearing loss in which waves don’t make it to the cochlea

• Caused due to a punctured eardrum, loss of vibration ability, and/or damage to the tiny bones of the middle ear.

How can Conductive hearing loss be fixed?

Hearing Aid

Sensorineural/Nerve Hearing Loss

Hearing loss due to old age, or damage to the hair cells.

• Caused due to damage to the cochlea, basilar membrane or hair cells in the inner ear. Likely due to loud noise.

How can Sensorineural/Nerve Hearing Loss be fixed?

Bionic Ear/Implants

Taste

Is a chemical sense

Gustation Receptor Cells

Located primarily on the tongue in the mouth.

• Five different types of taste

  • Salty, sweet, sour, bitter, umami

Damaged taste receptors (taste buds) are replaced…

Every few days

Touch

We feel sensations through touch receptors on the skin.

• Four basic types:

  • Pain, pressure, warmth, cold

Is spicy touch or taste?

Touch

Smell/Olfaction

Is a chemical sense

• Olfactory cells in upper nasal passage detect molecules in the air

• Does not recover after damage

• 10,000+ detectable smells

_____ is the only sense that directly transmits information to the temporal lobe, bypassing the thalamus

Smell

Flavor is…

Taste and Smell combined

Olfactory Cells

The chemical receptor cells for smell

McClinkok Effect

Menstrual cycle of close friends/roommates coincides (pheromones)

Kinesthetic Sense

The system for sensing the position and movement of individual body parts

• Relies on receptor cells from the muscles and joints

Vestibular Sense

The system for sensing body orientation and balance, which is located in the semicircular canals of the inner ear.

• Relies of fluids in the canals.

Perception

The process of organizing and interpreting incoming sensory information from sensory organs.

• We may all see the same information, but we perceive it differently

Figure-Ground

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

• The figure is the object(s) that stand out or draw one’s attention

  • Ground is the background

Selective Attention

Focusing conscious awareness on a particular stimulus to the exclusion of others

• The ability to focus on one stimulus at a time

• Allows a person to function in a world filled with many stimuli

Gestalt

The whole, or the organizational patterns that we tend to percieve

• By breaking experiences into their basic parts, something important is lost.

Grouping

The perceptual tendency to organize stimuli into understandable units. 4 types.

Grouping - Similarity

The tendency to place items that look similar into a group

Grouping - Proximity

The tendency to place items that are physically close into a group

Grouping - Continuity

The tendency to perceive that movement of an object continues once it appears to move in a particular direction

Grouping - Closure

The tendency to look at the whole by filling gaps in a perceptual field

Feature Analysis

Detecting specific elements parts or movements

Feature Detectors

Nerve cells in the brain that respond to specific features of the stimulus, such as lines, shapes, angles, or movement.

Top-Down Perceptual Processing

Information processing that draws on expectations and experiences to interpret incoming sensory information

Bottom-Up Perceptual Processing

Information processing that analyzes the information coming from your senses

Depth Perception

The ability to see in 3D and to judge distance. Needs 2 eyes.

Visual Cliff

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

• Many animals (including infants) are reluctant to crawl to the “edge” of the “cliff”, suggesting that to an extent, depth perception is inborn.

Binocular Cues

Depth cues that require the use of both eyes

Retinal Disparity

A binocular depth cue resulting from slightly different images produced by the retina of the left eye and the retina of the right eye

Convergence

A binocular depth cue related to tension in the eye muscle, when the eyes track inwards to focus on objects closer to the viewer.

• The more tension in the eye muscle, the closer the object.

Monocular Cues

Visual signals that allow a single eye to perceive certain aspects of depth, distance, and form

Monocular Depth Cue - Relative Size

Using the perceived size of a familiar object to determine depth. The larger the object appears, the closer the object is to the viewer

Monocular Depth Cue - Interposition

Method of determining depth by noting that closer objects partially obstruct the more distant objects. Also called “overlap”

Monocular Depth Cue - Texture Gradient

Method of determining depth by noting that distant objects have a smoother texture than nearby objects