Sensation and Perception

Sensation

The stimulation of sensory receptors and transmission of sensory information to the central nervous system

Where are sensory receptors located?

Eyes, ears, skin, etc

Where does stimulation come from?

Sources of energy, light and sound (automatic processes)

Perception

Process where sensations are organized and interpreted to form inner representations of the world

Absolute Threshold (Gustav Fechner)

Weakest amount of stimulus that a person can distinguish from no stimulus at all

Pitch

Highness or lowness of a sound

Difference Threshold

Minimum difference in magnitude of two stimuli required to tell them apart

Weber's Constant (Ernst Weber)

The perceived difference in the intensity of light (2% or 1/60th)

Just noticeable difference

Minimum difference in stimuli that a person can detect (2% or 1/50th)

Signal Detection Theory

View that perception of sensory stimuli involves the interaction of physical, biological and psychological factors

Light

Visible light that triggers visual sensation

Hue

Color of light, determined by wavelength

Cornea

Transparent tissue forming the outer surface of the eyeball

Iris

Muscular membrane whose dilation regulates the amount of light that enters the eye

Pupil

Black looking opening in the center of iris through which light enters

Lens

Adjusts/accomodates to the image by changing its thickness and focuses image on the retina

Photoreceptors

Cells that respond to light

Bipolar Cells

Neurons that conduct neural impulses form rods and cones to ganglion cells

Ganglion Cells

Neurons whose axons form the optic nerve

Optic Nerve

Nerve that transmits sensory information from the eye to the brain

Retina

Inner surface of eye that consists of cells called photoreceptors

Rods (125 Million distributed across retina)

Rod shaped photoreceptors that are sensitive only to the intensity of light and allow you to see in black and white

Cones (6.4 Million distributed across retina)

Cone shaped photoreceptors that transmit sensations of color that provide color vision

Visual Acuity

Sharpness of vision (strongest in retina)

Presbyopia

Condition characterized by brittleness of lens

Dark Adaptation

Process of adjusting to condition of lower lighting by increasing the sensitivity of rods and cones

Complementary

Descriptive colors of the spectrum that when combined produce white or nearly white light

Red is complementary to

Green

Purple is complementary to

Yellow

Blue is complementary to

Orange

Additive Process

Mixture of lights

Subtractive Process

Mixture of pigments

Afterimages

Lingering visual impression made by a stimulus that has been improved/Persistent sensations of color are followed by perception of the complementary color when the first color is removed

Trichromatic Theory

Theory that color vision is made possible by three types of cones, some of which respond to red light, some to green and some to blue

Opponent-Process Theory

Theory that color vision is made possible by three types of cones, some of which respond to red or green light, some to blue or yellow and some to the intensity of light

Trichromat

Person with normal color vision

Monochromat

Person who is sensitive to black and white only (colorblind)

Dichromat

Person who is sensitive to black-white and either red-green or blue-yellow and hence partially colorblind

Closure

Tendency to perceive a broken figure as being complete or whole

Visual Perception

Process is the process by which we organize or make sense of the sensory impressions caused by the light that strikes our eyes

Gestalt

Perception of the whole, has parts that organize into a whole which is different from sum of parts

transposition

Rubin Vase

Correlates to the figure-ground perception that created reversible figures and contours

Proximity

Nearness, perceptual tendency to group together to group together objects that are near one another

Similarity

Perceptual tendency to group together objects that are similar in appearance

Continuation

Tendency to perceive a series of points or lines as having unity

Common Fate

tendency to perceive elements that move together as belonging together

Top Down Processing

The usage of knowledge to organize parts of a pattern

Bottom Up Processing

Organization of parts of a pattern to recognize

Illusions

Sensations that give rise to misperceptions

Stroboscopic Motion

Illusion in perception of motion which uses presented stationary images in a rapid succession

Monocular Cues

Cues that can be perceived by only one eye

Perspective

Cue for depth based on the convergence of parallel lines as they recede into the distance

Texture Gradient

(monocular)Cue based on perception that closer objects appear to have rough surfaces

Motion Parallax

Cue for depth based on perception that nearby objects move more rapidly than our own motion

Illusions of Magnitude

deals with people misperceiving how big something is, happens to anybody

(Vertical Horizontal Illusion, Progondorf Illusion, Worthimer Illusion of Kind (formed psychology of gestalt)

Decibal

Measures sound

Kohler

Formed laws of organization on perception

Perceptual Constancy

points to instances where our perception of something remains the same (even if stimulus has changed)

Examples of this are: brightness constancy, color, shape, orientation, size

Convergence

Binocular cue based on inward movement and focus of eyes as an object draws nearer

Accommodation

When our lens focuses the incoming light when hitting our retina

Binocular Cues

Involves simultaneous perception by both eyes

Cochlea

Inner ear, contains basilar membrane and organ of corti

Basilar Membrane

Lies coiled inside cochlea

organ of Corti

Receptor for hearing that lies on basilar membrance

Auditory Nerve

Axon bundle that transmits neural impulses from organ of Corti to brain

Five Basic Dimensions of Taste

Sourness, saltiness, sweetness, bitterness, umami (richness)

Smellen Chart

Measures visual activity

Retinal Disparity

Proves that one image is different to one eye compared to the other when distance is involved