Actual Perception Final

Sensation

Ability to detect stimulus and turn the detection into a private experience

Perception

Act of giving meaning to detected sensation

Materialism

The only thing that exists is matter and all things, mind and consciousness, results from interactions of matter

Psychophysics

The science of defining quantitative relationships between physical and psychological events

Just Noticeable Difference (JND)

Smallest detectable difference between two stimulus or minimum change that can be correctly judged

Absolute threshold

Minimum amount of energy to just detect stimulus or 50% of the time, just beyond chance

Method of constant stimulus

Many stimulus rarely to almost always perceptible at one time

Method of adjustment

Observer controls strength of stimulus until criteria is matched

Magnitude of estimation

Participant assigns values according to perceived magnitudes of stimulus

Cross-modality matching

Matches intensity of stimulus with intensity of different sensation

Signal detection theory

Response to presentation of signal in presence of noise

Hit

Got out of shower, phone ringing

Miss

Did not get out of shower, phone ringing

Correct rejection

Did not get out of shower, phone not ringing

False alarm

Did get out of shower, phone not ringing

Criterion

Internal thresholds set by observer

Sensitivity

Value that defines ease that observer can tell difference between presence and absence of stimulus or difference between stimulus 1 and stimulus 2

Fourier analysis

Mathematical procedure where signal is broken down into many different sine waves

Spatial frequency

Number of white and black stripes per square inch

Doctrine of specific nerve energies

Hitting your head and seeing stars or light, mechanical input or visual input = nerve activated

Synapse

Junction between neurons that allows info transfer

Neurotransmitter

Chemical substance used in neuronal communication at synapses

EEG

Electrodes on scalp, electrical activity from many neurons

fMRI

Blood oxygenation change with activated neurons

Psychophysics founder

Fechner

Signal detection theory uses

Both signal and noise

Reflection

Hits surface and comes back

Absorption

Hits and does not come back

Refraction

Hits and is altered

Aqueous humor

Watery fluid in anterior chamber

Vitreous humor

Gel-like fluid, fills large chamber, holds eye shape

Pupil

Dark circular opening in center of Iris

Iris

Colored muscle, expands or contracts pupil

Lens

Focus image into back of eye

Retina

Light sensitive membrane, contains rods and cones at back of eye

Myopia

Nearsightedness, long eye

Transduction

Process of light energy turning into electrical energy in photoreceptors

Rods

Night vision, no color

Cones

Daytime vision, fine visual acuity, color vision

Fovea

Very high resolution spot in vision, for focus

Lateral inhibition

Antagonistic interaction of adjacent areas of the retina

Ganglion

Retinal cells, axons leave eye through optic nerve

ON-Center ganglion cells

Spot of light in center, dark ring around

Off-Center ganglion cells

Ring of light, dark in center

P ganglion cell features

More sensitive to color, small

M ganglion cell features

Less sensitive to color, large

Highest number of cells in eye

Rods

Light and dark adaptation

Changes in photoreceptor concentration and pupil constriction/dilation

Contrast

Difference in illumination between figure and its background

Acuity

Smallest spatial detail resolved at 100% contrast, good in fovea, bad in periphery

Visual angle

Size an object takes on retina

Contrast sensitivity

Function of how spatial frequency and contrast interact to make grading more/less visible

Lateral Geniculate nucleus (LGN)

Axons of retinal ganglion synapse to either, have two

Topographical mapping

Orderly mapping of the world in LGN and Visual cortex

Orientation tuning

Tendency of neurons in V1 or striate cortex to respond optimally to some orientations but not others

Complex cells

Neurons WITHOUT clearly defined excitatory or inhibitory regions

Simple cells

Neurons WITH clearly defined excitatory or inhibitory regions

Hypercolumn

1 mm chunk on V1 with two sets of columns with cells that cover all orientations, 1 prefers left and 1 prefers right

Adaptation

Diminishing response in sense organ to sustain stimulation

Strabismus

Misalignment of both eyes

Amblyopia

Reduced spatial vision in healthy eye

Neurons in LGN

Magnocellular, Parvocellular, Koniocellular

Other visual cortex names

Area v1, primary visual cortex, striate cortex, area 17

What does 20/20 vision mean? 20/500?

At 20 ft away you can see an image that a standard observer can see at 20 ft away. At 20 ft away you can see an image that a standard observer can see at 500 ft away

Left eye = ? visual cortex

Right

Right eye = ? visual cortex

Left

Grandmother cell

Cell that responds best to one specific object person (grandma/Jennifer Aniston)

Agnosia

Failure to recognize objects even though you can physically see them

Feed-forward process

Process that carries computation sequentially without need for feedback from later stage

Illusory contours

Gestalt psychology theory

Perceptual whole is greater than sum of its parts

Gestalt principle common region

Things in same area appear visually grouped together

Gestalt principle synchrony

Things that change at the same time are grouped together

Bayesian theory

Prior knowledge of world plus current stimulus

FFA: fusiform facial area

Process faces more than other objects

PPA: parahippocampal place area

Process places like a picture of a house

EBA: Extrastriate body area

Process body parts

Geons

Object representations according to structural model of object recognition like cylinder cone pyramid wine glass

Structural model of recognition

Recognize objects by breaking things down into subunits (geons)

Template model of recognition

Stored pattern for everything in the whole world at every angle and size

Prosopagnosia

Inability to identify faces but can identify other objects

Re-entrant process

Process in brain that sends signals back downstream to earlier areas in processing higher to lower

Process _____ features in image before _____ features

Global; local

Photopic lighting

Day

Scotopic lighting

Night

Principle of Univariant

Infinite combinations of wavelength and intensity that give same response if looking at one photoreceptor

Metamers

Different mixtures of wavelengths that look identical

Number of lights needed to match any color humans can see

Three lights = three types of photoreceptor

Cone opponent cells

Cells in LGN that compute chromatic differences

Opponent color theory

Theory that perception of color is based on the output of three cones, each an opponent of two colors

Color opponent pairs

Red-green, yellow-blue, black-white

Where double opponent cells are first found

Visual cortex

CIE diagram

Representation of color used as standard for paint and plastic makers, way of categorizing color numerically

Hue

What color something is

Saturation

How vivid is color

Brightness

How dark or light is color

Deuteranope

Colorblind person due to absence of M cones

Additive color mixing

Shining lights together to make one color, end up with white

Subtractive color mixing

Mixing paint, end up with black

Rod Monochromat

Someone with no cones