Exam 2 - Psy 331

Divided Attention

paying attention to more than one thing at one time

Sustained Attention

ability to focus on a specific task for a continual amount of time

Selective Attention

focusing on specific objects and filtering out others

What are two ways attention is selected?

Endogenous (you choose) and exogenous (environment chooses)

What are two ways eye movements is measured?

Saccades and fixations

Saccades 

small, rapid eye movements 

Fixations

pauses in eye movements that indicate where a person is attending (three fixations per second)

Stimulus Salience

areas of stimuli that exogenously capture attention due to their properties (i.e. color, contrast and orientation)

Scene Schema 

prior knowledge about what is found in typical scenes (fixations are influenced by this knowledge) 

Inattentional blindness

a stimulus is not perceived even when a person is looking directly at it

Change blindness 

a change from one image to another is not noticed

Binding

process by which features are combined to create perception of coherent objects

Binding problem 

features of object are processed separately in different areas of the brain

Treisman and Gelade - Feature Detection Theory

Preattentive stage

features of objects are separated

Focused attention stage 

features are bound into a coherent perception (attention is solution to binding problem)

Conjunction Search 

finding target with 2 or more features (Where’s Waldo) 

Illusory Conjunctions

features that should be associated with an object become incorrectly associated with another

Balient’s Syndrome: patients with parietal lobe damage show lack of focused attention results in incorrect combinations of features 

Akinenotopsia

both sides of brain damaged (medial temporal area)

Attention capture 

motion attracts attention to the moving object 

movement of objects or the observer’s movement through object assists in organization of stimuli 

Real motion

an object is physically moving

Monkey and Dots Experiment 

As coherence of dot increased: 

1. middle temporal (MT)neuron activity for that direction increased 

2. Judgement of movement accuracy by monkeys increased 

3. MT context activated by specific direction

4. Monkey more likely to select artificially stimulated directions

1st Situation of Movement 

An object moves, and the observer is stationary. Movement creates an image that moves on the observer’s retina

2nd Situation of Movement

An object moves and the observer follows the object with their eyes. The image is stationary on retina

3rd situation of movement

An observer moves their eye. Image of environment moves across retina but environment is perceived as stationary

Corollary Discharge Theory 

Movement perception depends on three signals: motor, corollary discharge signal and image displacement signal 

*Motion perceived if CDS or IDS occurs, but not both at the same time

Motor 

signal sent to eyes to move eye muscles 

Corollary Discharge signal

split from motor signal (secondary signal)

Ex. Look at Dr. Miles. follow him as he moves

Image Displacement Signal

movement of image stimulating receptors across the retina

Ex. Stare at box, Dr. Miles move across from it (something move across eye)

An example of motion not perceived

Look at circle, move eyes to another area: IDS and CDS occurs

What do neurons in Extrastriate cortex in monkeys respond to? 

Responds when a stimulus moves and do not respond when eye moves 

Optic Array

structure created by surfaces, textures, and contours, which change as the observer moves through environment

Ex. Navigation

Global Optic Flow

overall movement of optic array and indicates observer is moving not environment

Ex. standing still while boat is moving or virtual reality

Moving forward 

vision expands 

Moving backward

vision implodes

Local disturbance in optic array

actual moving objects will cause a small area to “flow” differently than rest

Aperture (hole) problem 

Direction of a part of a moving object does not always provide enough information about how whole object is moving 

Solution to aperture problem

how ends of object move determines how you see parts moving (end-stopped cortical cells)

Biological motion

movement of person or other living organism

Ex. how a person is walking determines their emotions; walking fast = nervous

Point-light walker stimulus 

biological motion made by placing lights in specific places on a person

Motion aftereffect 

movement appears to occur in opposite direction from the original (sometimes called the waterfall illusion) 

Illusory motion

apparent movement between objects where stationary stimuli are presented in slightly different locations (looks like its moving)

The Phi Phenomenon

Ex. movies where still pictures are combined fast enough to create motion

Shortest Path Constraint 

Ex. hand going around the head instead of through the head 

Larson et al. (2006) experiment

Participant is scanned by an fMRI while viewing three displays

perception of motion in both cases is related to the same brain mechanism

Possible explanation for illusory motion 

Believed to involve motion sensitive cells and changes in contrast leading to similar activation as real motion and phi phenomenon (light and dark areas combined) 

Induced motion

movement of one object results in the perception of movement in another object

Ex. background moving makes it feel like Mario is moving forward but is actually just running in one place

Implied motion

imagining motions suggested by images 

pictures that are stationary depict an action that involves motion Re

Representational Momentum

observers show that the implied motion is carried out in observer’s mind (activity in medial temporal area)

Color

How we experience different wavelengths of color (400-700nm) out of all the electromagnetic spectrum field

Superimposition

different wavelengths of light at the same location don’t mix into one wavelength of light - they exist separately in the same location like a rainbow

Achromatic colors 

contain no hue (white, black and gray tones) 

Colors can be changed by:

hue, saturation, and intensity

Hue

changing wavelengths (short, medium, long)

Saturation 

adding white (all wavelengths) to a color results in less saturated color; purely one type of wavelength shows one color 

Ex. short wavelength = blue color or pink is desaturated long wavelengths 

Intensity

energy or amount of light (think of the color experience of black)

Additive Color Experience

mixing lights of different wavelengths

superimposing short and medium with long light waves leads to perception of white

What two wavelengths make what color? 

Trichromatic Theory (Young and Helmholtz, 1800s)

three cone types that are sensitive to different ranges of wavelengths

combinations of responses across all 3 cones types lead to perception of all cones (*need to know what all 3 cone’s wavelength is to determine color) 

Metamers 

colors that are perceptually similar can be caused by different physical wavelengths 

Ex. yellow can be seen either be seen in one single long or medium wavelength or long and medium at the same time 

Subtractive Color mixing

starting with all wavelengths and then subtracting short, medium, or long

Ex. yellow takes away short wavelength (absorb short, reflect long and medium)

Selective reflectance

colors of objects are determined by the wavelengths that are reflected rather than absorbed

Opponent-Process Theory of Color Vision 

colors are discriminated by opposing responses generated by blue and yellow and by green and red 

Circuits located in retina and LGN (like a seasaw): tells the difference 

Respond in an opposing fashion, such as negatively to red and positively to green (the neuron fires more for green but fire less for red)

Behavioral evidence of Opponent-Process Theory 

color afterimage, simultaneous color, and color blindness 

Color Afterimage

Stare at blue for a while, neurons tire out for short wavelength cone and will see yellow instead

Simultaneous color contrast

you see yellow in gray X from blue box because blue is sending lateral inhibition to X, suppressing the blue and bleu is opposite of yellow

Monochromats

one (or no) types of cones, only rods, ability to perceive only in white, gray, and black tones

True blindness, poor visual acuity, very sensitive eyes to bright light

Dichromat 

two cone types (most common blindness) 

3 types: protanopes, deuteranopes, and tritanopes 

Protanopes

can’t tell the difference between red and green, long wavelength cone circuit cut

Deuteranope 

can’t tell the difference between red and green, medium wavelength cone circuit cut 

Tritanopes

yellow/blue color blindness

Trichromatic Theory vs. Opponent-Process

explains how you discriminate wavelengths of light vs. explains why colors look distinctive in your mind

Chromatic Adaptation 

adapting when the stimulus color selectively bleaches a specific cone pigment 

Ex. too much red (long wavelength), you become less sensitive to it

Effect of Surroundings

works best when an object is surrounded by many colors

Ex. Unred gray — cyan (brain does if there’s too much of the same colors, in this case, red and goes to opponent color) 

Memory and color

past knowledge impacts color perception

Lightness constancy

lightness perception under uneven illumination

Reflectance edge

edges where the amount of light reflected changes (changes in surface color, material, or texture) 

Illumination edges

edges where lighting of two surfaces changes (change in light intensity or direction)

Ex. hand and its shadows

Oculomotor Cues 

convergence and accommodation 

Convergence

inward movement of eyes when we focus on nearby objects (requires 2 eyes)

Accommodation

change in the shape of the lens when we focus on objects at different distances (requires 1 eyes only)

Monocular Cues (Pictorial)

occlusion, relative height, relative size, perspective convergence, familiar size, atmospheric perspective, texture gradient

Occlusion 

when one object partially covers another (an object is perceived as closer when it is in front) 

Relative height 

objects below the horizon that are higher are more distant (the higher an object is touching the ground, the farther it is away from you) 

Ex. point down = closer, point up = further (ground) 

Point straight up = closer, point up at an angle = further (sky) 

Relative size

when objects are equal size, the closer one will take up more of your visual field (object looks bigger, it is closer to you)

Perspective convergence

parallel lines appears to come together in the distance

Familiar size

distance information based on our knowledge of object size

Ex. spider is small but it only looks bigger b/c it is closer up on your face)

Atmospheric perspective

distance objects are fuzzy and have a blue tint

Texture gradient

equally spaced elements are more closely packed as distant increases

Ex. trees

Shadows

indicate where objects are located (enhance 3-D of objects)

Monocular Cues 

Motion parallax and deletion and accretion 

Motion parallax

close objects in direction of movement glide rapidly past but objects in the distance appear to move slowly

Ex. when driving, closer objects move fast across your sign (like a sign) but further objects like mountains move slowly across your eye

Deletion and accretion

objects are covered (deletion) or uncovered (accretion) as we move relative to them

the further two objects are apart, the faster an object is covered and uncovered

Binocular Depth Information 

horopter, corresponding retinal points, binocular disparity, absolute disparity, relative disparity 

Horopter

imaginary line through everything that is the same distance you are looking

Corresponding retinal points

matching points of the two retinas (everything on the horopter makes images with corresponding retinal points)

Binocular disparity 

anything a different distance away than where you are looking will have mismatching locations on the left and right away 

Absolute disparity (different)

difference from corresponding retinal points from an image

Ex. the difference from the location of both eyes (center and matched) looking at an object that is closer or further from the original object

Relative Disparity

the difference in absolute disparities between two image

Binocular Depth Cells

aka disparity selective cells

Responds best to specific degree of absolute disparity between images on the right and left retinas

Frontal eyes 

result in overlapping fields of view are necessary for binocular disparity