Sensory Processes Exam 2

Fixation

brief pause occurring between eye movements as a scene is scanned

Saccade

rapid eye movements occurring as the eye moves to a new fixation spot

overt attention

looking directly at the attended object

covert attention

attention without looking

measuring engagement

eye movement and fixation

visual salience

areas of stimuli that attract attention due to their properties (color, contrast, and orientation). highest visual salience = attentional capture

saliency map

determined by analyzing color, contrast, and orientation in a scene

attentional capture

occurs when stimulus salience causes an involuntary shift of attention (movement)

picture meaning

helps our brains prioritize important elements in a scene

observer knowledge

structures into schemas involve our prior knowledge about what is typically in scenes

fixation influence

observer knowledge and picture meaning

enhancement effect

attention is spread across attended object, not just cued location. observed for non-target locations within the same object

binding

process by which features are combined to create a unified perception of an object. Integrates separate features into a single coherent perception, the process involves feedback from higher to lower visual areas to refine and integrate sensory input

binding problem

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

feature integration theory

explains how an object is broken down into features and how these features are recombines to result in a perception of the object

pre-attentive

stage in which a stimulus is decomposed into individual features

focused attention

stage of processing in which features are combined

illusory conjunction

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

balint’s syndrome

lack of focused attention and ability to shift attention with multiple objects in a scene. due to damage in parietal lobe

conjunction search

searching for a combination of two or more features in the same stimulus. needs top--down focused attention with conjunction or small differences

inattentional blindness

where an individual fails to perceive an unexpected stimulus in plain sight because their attention is engaged on another task, event, or object

change blindness

failure to notice something different about a display

task irrelevant stimuli

any sensory input unrelated/unnecessary for the completion of a specific task

optical flow

appearance of objects as the observer moves past them

gradient of flow

difference in flow as a function of distance from the observer

focus of expansion

point in distance where there is no flow

invariant information

properties that remain constant while the observer is moving

self produced information

sensory feedback that individuals generate as a result of their own actions (visual, auditory, or proprioceptive cues)

visual direction strategy

observers keep body pitned toward target and correct heading based on movement

blind walking experiment

people can navigate without any visual stimulation from the environment

wayfinding

navigating to a target location using memory of routes and landmarks

landmarks

objects on route that serve as cues indicating where to turn

path integration

estimates current position, providing direction and distance for a return journey

wayfinding experiment

greatest activation for objects at decision points in the parahippocampal gyrus

cognitive map

mental representation of the spatial layout and relationship of one’s environment. formed by 3 types of cells (place, head direction, and grid cells)

place cells

specific hippocampal neurons that activate when an animal reaches a particular location

head direction cells

neurons in the entorhinal cortex that turn-on when facing a specific direction

grid cells

neurons that fire in a grid like pattern for spatial coordination/when moving a specific distance

affordances

what objects are used for, indicate a potential for action,

brain damage - affordances

even if they cannot name objects they can still describe how they are used/pick them up/ use them

monkey handgrip experiment - Fattori

parietal reach region was targeted. shows distinction of dorsal and ventral pathway. dorsal - placement of fingers and hands. ventral - responsible for object identification

mirror neurons

respond when monkey grasps an object at the same time as an experimenter. can help to understand another animals actions and react to them appropriately. can also help imitate observed actions. may help link sensory perceptions and motor actions

audiovisual mirror neurons

respond to action and accompanying sound

JJ Gibson

argues that traditional laboratory approaches fail to capture how we perceive our environment while moving through it, resulting in ecological approach

attentional capture

motion attracts attention to the moving object

akinetopsia

motion blindness or inability to discern movement or direction of movement

real motion

object is phsically moving

illusory motion

perception of motion when there actually is none

apparent movement

stationary stimuli presented in slightly different locations, basis of movement in movies and TV

induced motion

movement of one object leads to the perception of movement in another object

motion aftereffect

looks at movement for 30-60s and then looks at stationary object, the movement appears in the opposite direction from the original motion

reichardt detectors

neurons that fire to movement in one direction

ecological approach

focuses on specifying the information in the environment used for perception, emphasizing the study of moving observers to determine how their movement results in perceptual information that both creates perception and guides further movement

optic array

structure of light created by surface textures and contours. changes as observer moves through environment

local disturbance in optic array

objects move relative to background. parts of background are covered/uncovered

global optic flow

overall movement of optic array. indicated observer is moving, not the environment

eye fixation

stabilizing gaze direction during movement

corollary discharge theory

explains motion perception as being determined both by movement of the image on the retina and by signals that indicate movement of the eyes

when is movement not percieved

when the comparator perceives both the CDS and IDS simultaneously

image displacement signal

movement of an image across the retina that stimulates receptors

motor signal

command sent to eye muscles to move the eye

corollary discharge signal

copy of the motor signal sent to other brain areas, AKA efference copy

Motion perception - Newsome

varied coherence of dots moving. MT neurons measured, monkeys judge direction of dot movement. → increased coherence of dot movement leads to increased MT neuron firing and movement accuracy judgements

aperture problem

being misled about direction of movement when observing a small portion of a larger stimulus

biological motion

movement of a person or other living organism that can be observed through apparent motion in point-lighted displays

point-light walker stimulus

biological motion is made and can be studied by placing lights in specific places on a person

where biological motion is processed

STS (superior temporal sulcus) and FFA (fusiform face area)

striate cortex motion perception

direction of motion across small receptive fields

middle temporal area motion perception

direction and speed of object motion

medial superior temporal area motion perception

processing optic flow; locating moving objects; reaching for moving objects

superior temporal sulcus motion perception

perception of motion related to animals and people (biological motion)

implied motion

still pictures that depict an action that involves motion

representational momentum

motion depicted in a still picture continues in an observer’s mind

spectral colors

colors that appear in the visual spectrum

non-spectral colors

colors that do not appear in the spectrum because they are mixtures of other colors

saturation

the relative amount of whiteness and achromatic colors, the less white the more saturated

value

the light to dark dimension of color

Short wavelength reflected or transmitted

blue

medium wavelength reflected or transmitted

green

long and medium wavelength reflected or transmitted

yellow

long wavelength reflected or transmitted

red

long, medium, and short wavelength reflected or transmitted

white

additive color mixing

mixing lights of different wavelengths

subtractive color mixing

mixing pigments results in fewer wavelengths being reflected

trichromatic theory of color vision

observers with normal color vision need 3 wavelengths to make color matches, those with color deficiencies only need 2 wavelengths

visual pigment receptor maximals

S - 419nm

M - 531nm

L - 558nm

metamers

colors that are perceptually similar (530+620nm = 580nm)

behavioral evidence for opponent-process theory of color vision

color afterimages and simultaneous color contrast show opposing pairings

types of color blindness are red/green and blue/yellow

opponent neurons

located in retina and LGN; respond in an excitatory manner to one end of the spectrum and an inhibitory manner to the other end

trichromatic theory

explains the responses of the cones in the retina

opponent-process theory

explains neural response for cells connected to the cones further in the brain

color in the cortex

no single module for color perception, cortical cells in V1&4 respond to some wavelengths or have opponent responses; also respond to forms and orientations. cortical cells that respond to color may also respond to white

double opponent neurons

excited by certain types of light in the center and inhibited by others in their surrounding area, they are able to detect color contrast better than single-opponent neurons.

double opponent neurons function

enhancing color boundaries, improving color constancy, and supporting fine color discrimination

color constancy

relatively constant color perception despite changing light sources

chromatic adaptation

occurs when prolonged exposure to chromatic color leads to adapting (stimulus color bleaches a specific cone pigment) and decreasing in sensitivity to that color

achromatic colors

perceived as remaining relatively constant; color without hue

perception of lightness

unrelated to amount of light reflected by an object, is related to the percentage of light reflected by an object

ratio principle

when two areas that reflect different amounts of light look the same if their ratios of intensities are the same. this works when objects are evenly illuminated

reflectance edges

edges where the amount of light reflected changes between two surfaces