PSYC 102 Exam 5/22 Flashcards
Akinetopsia
Blindness to motion
Attentional capture
Motion attracts attention to the moving object
How do we perceive things more rapidly and accurately? (related to movement)
Movement of objects or the observer’s movement through objects assists in perceiving things more rapidly and accurately because you are getting more information about the object
What are he two types of motion
Real motion and illusory motion
Real motion
An object is physically moving
What are the 3 types of illusory motion
Apparent movement, Induced motion, motion aftereffect
Apparent movement
Stationary stimuli are presented in different locations and it looks like movement, used in movies and TV
Induced motion
Movement of one object results in the perception of movement in another object. Eg: Moon and clouds. When the clouds drift it looks like the moon is moving
Motion aftereffect
When a stationary object or scene appears to move in the opposite direction after prolonged exposure to motion in one direction, eg: waterfall looks like it is flowing backwards even though it isn’t
The are of the brain utilized for real AND apparent motion is…
The same brain mechanism in the visual cortex
Movement creates an image that…
moves on the observer’s retina
Ecological approach to motor perception
Information is directly available in the environment for perception
Optic array
Structure created by surfaces, textures, and contours, which change as the observer moves through the environment
Global optic flow
Overall movement of optic array; Indicates that observer is moving and not the environment
Reichardt detectors
Neurons that fire to movement in one direction; Receptors of particular movement (light response) will activate and go to the final location, end of circuit
Corollary Discharge theory
Movement perception depends on 3 signals; Image displacement signal (IDS), Motor signal (MS), and Corollary Discharge Signal (CDS)
Image Displacement Signal (IDS)
Movement of image stimulating receptors across the retina (Eye is stationary, stimulus is moving)
Motor signal (MS)
Signal sent to eyes to move eye muscles
Corollary discharge signal (CDS)
Signal split from motor signal (carbon copy sent elsewhere)(Eye follows moving stimulus)
Movement is perceived when comparator receives input from…
Corollary discharge signal OR Image displacement signal
Movement is NOT perceived when comparator receives input from…
BOTH CDS and IDS
Real movement neurons in monkeys respond only when…
a stimulus physically moves not when eyes move
Motion perception (direction) in the brain happens in….
Medial temporal (MT) neurons; Respond to a specific direction when activated
The firing and coherence experiment by Newsome et al on monkeys
As coherence of dot movement increased (dots in the same direction) the firing of the MT neurons increased and so did judgement of movement accuracy
Aperture problem
Observation of a small portion of a larger stimulus leads to misleading information about direction of movement
Complex cortical cells respond preferentially to an oriented bar moving in a specific direction
Activity of a single complex cell does not provide accurate information about direction of movement
To solve the aperture problem
Responses of V1 neurons are pooled
Neurons in the striate cortex respond to movement of…
ends of objects
Biological movement
movement of a person or other living organism
Point light walker stimulus
Biological motion replicated by points of light in specific places (usually joints) on a person; structure-from-motion
Which parts of the brain are more active when perceiving biological motion
Superior temporal sulcus (STS) and Fusiform face area (FFA)
Transcranial magnetic stimulation
Applied to STS to detect biological motion better in a scramble of dots
Representational momentum
Motion responses to still pictures (Implied motion pictures); observers show that the implied motion is carried out in the observers mind
Implied motion
Still pictures that depict and action that involves motion
Areas of the brain responsible for motion fire in response to pictures of implied motion are…
MT and MST
Movement creates perceptual information
Optic flow to get more information about surroundings and elicit appropriate response
optic flow
appearance of objects as the observer moves past them
Gradient of flow
difference in flow as a function of distance from the observer (information from surroundings)
Focus of expansion
Point in distance where there is no flow (stays static)
Invariant information
Properties that remain constant while the observer is moving (usually in the focus of expansin)
Self produced information
Flow is created by movement of the observer; movement creates flow and flow provides information to further guide movement
Summersault (self produced information)
It is the same with and without vision BUT expert gymnasts use vision to correct their trajectory so they perform better with their eyes open, novice gymnasts do better with their eyes closed
The senses do not work in isolation
Vision is important for balance; with lack of vision other senses come into play to adjust the body (swinging room experiment)
Swinging room experiment
Movement of walls creates optic flow and makes children AND adults sway bac and forth, losing balance. Vision has a powerful affect on balance and even overrides other senses that provide feedback about body placement and posture
Navigation through the environment
simple lines and their direction = movement/optic flow neurons
Optic flow neurons
Neurons in the medial superior temporal area (MST) that respond to flow patterns
Monkey experiment by Britten and Van Wezel about optic flow neurons
Specific neurons like different types of movement, Stimulating those specific neurons made the monkeys shift their attention to the specific direction of flow patterns
Functions of color vision
classify and identify objects, evolutionary advantage for foraging food
Colors of objects are determined by…
Wavelengths of light that are REFLECTED
Chromatic colors or hues
Objects that preferentially reflect some wavelengths (Selective reflection); all of the color wavelengths are absorbed by the object and the color is the only thing reflected
Selective transmission
Transparent objects selectively allow wavelengths to pass through
Short wavelengths
Blue
Medium wavelengths
Green
Long + medium wavelengths
Yellow
Long wavelengths
Red
All wavelengths
White
Trichromatic theory of color vision
3 different receptor mechanisms are responsible for color vision; proved through a color matching experiment by adjusting 3 wavelengths in a comparison field. Results showed that observers need atleast 3 wavelengths to make the correct matches
Cone response to color perception
Color perception is based on 3 types of cones. Combinations of responses from all 3 cone types lead to perception of colors based on the color wavelength. Relationships between cones is important because more patterns of activity helps us perceive more information
One type of receptor cannot lead to color vision because…
1) Absorption of one photon causes the same effect, no matter what the wavelength is. 2) Any 2 wavelengths can cause the same response by changing the intensity, this isn’t possible with one type of receptor
Why are 3 receptors better than 2?
While two receptors can help adjust the response to wavelengths three is better for perception of more colors
Monochromat
True color blindness, only needs one wavelength to match colors, world is black and white and have eyes that are sensitive to bright light. Tend to only have rods, without any functioning cones
Dichromat
Person who only needs two wavelengths to match any color
3 types of dichromatism
Protanopia, Deuteranopia, tritanopia
Protanopia
World perceived in blues, yellows, and greens. Missing the long-wavelength pigment
Deteranopia
World perceived in blues greens, and yellows but missing medium wavelength pigment
Tritanopia
Pinkish, reds and blues. Probably missing short wavelength pigment
Anomalous trichromat
Needs 3 wavelengths in different proportions than a normal trichromat
Unilateral dichromat
Trichromatic vision in one eyeand dichromat in another
Opponent-process theory of color vision
Color vision is caused by opposing responses generated by blue and yellow and by green and red. 3 mechanisms: red/green, blue/yellow, and white/black. the pairs respond in opposing fashion, positively and negatively for each color and result in chemical reactions in retina activity. Wavelengths either increase activity in bipolar and ganglion cells (Long/medium wavelengths) or decrease activity (short wavelengths)
Opponent neurons
Retina and LGN; respond in an excitatory manner to one end of the spectrum and an inhibitory manner to another
Color in the cortex
Opponent neurons: center surround and double opponent (orientation + color)
Color constancy
Perception of colors as relatively constant in spite of changing light source
Chromatic adaptation
Prolonged exposure to chromatic color leads to receptors adapting to a stimulus color and getting sensitive or tired to the wavelength. After prolonged exposure to a specific wavelength the wavelength in a different context looks muted.
Cue approach to depth perception
Information in the retinal image that is correlated with depth in the scene; occlusion; association between cue and depth
Oculomotor cues
Oculomotor cues are based on sensing the
position of the eyes and muscle tension
Convergence
Inward movement of the
eyes when we focus on nearby objects
Accommodation
change in the shape of
the lens when we focus on objects at
different distances
Monocular cues
Come from one eye; pictorial cues and motion produced cues
Pictorial cues
sources of depth information that come from 2-D images, such as pictures
Types of pictorial cues
Occlusion, Relative height, relative size, perspective convergence, familiar size, Atmospheric perspective, texture gradient, shadows
Occlusion
Whether one object partially covers another
Relative height
Objects below the horizon that are higher in the field of vision are more distant; Objects above the horizon and are lower
in the visual field are more distant
Relative size
when objects are equal size the closer one will take up more of the visual field
Perspective convergence
parallel lines appear to come together in the distance
Familiar size
distance information based on our knowledge of object size
Atmospheric perspective
distance objects are fuzzy and have a blue tint
Texture gradient
equally spaced elements
are more closely packed as distance increases
Shadows
Indicate where objects are located and enhance them as 3D
Types of motion-produced 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
Deletion and accretion
objects are covered or uncovered as we move relative to them
* Covering an object is deletion
* Uncovering an object is accretion
Binocular disparity
Difference in images from 2 eyes
Stereopsis
the impression of depth that
results from information provided by binocular
disparity; we need different input from both our eyes to better see objects in 3D
Strabismus
Eyes do not point in the same direction; lazy eye
Binocular depth cells/disparity selective cells
Neurons that best respond to binocular disparity; respond best to a specific degree of absolute disparity between
images on the right and left retinas.
Disparity tuning curve
At +1 disparity is when there is the highest neuron firing rate. Neurons with broad tuning curves are less specific and respond to a wider range of disparities, while neurons with narrow tuning curves are more selective and respond to a narrower range of disparities.
Alternating vision between two eyes reveals that
there is less activity of binocular neurons and we are unable to use binocular disparity to perceive depth
Distance and size perception are correlated
Visual angle depends on both the size of the object and the distance from the observer.
When given depth cues
Judgments of size were based on physical size.
When there is no depth information
Judgments of size were based on size of the retinal images.
Based on actual sizes of objects when there
is good depth information
When depth information is eliminated, visual
angle strongly influences size estimation
Size constancy
Perception of an object’s size remains relatively constant; this effect remains even if the size of the retinal image changes; size-distance scaling equation: S = R (Retinal images) X D (Distance) ; The changes in distance and retinal size balance each other
Cons of constancy
Inappropriate interpretations of physical reality
* Converging lines are corners -> Müller-Lyer illusion
* Linear perspective cues -> Ponzo illusion
* Rooms are rectangular -> Ames room illusion
Distance is
perceived as changing; Since the retinal images (R) are the same, the lines must be different sizes (S)
Ponzo illusion
Rectangular objects on a train track; The far rectangle appears larger than the
closer rectangle but both are the same size. One possible explanation is misapplied size-constancy scaling.
The Ames room
Two people of equal size appear very different in size in a normal-shaped room BUT The actual shape has the left corner twice as far away as the right corner, so the person looks small in the left. Explanation: size-distance scaling, Woman on the left has smaller visual angle
(R). Due to the perceived distance (D) being the same her perceived size (S) is smaller. OR Relative size explanation One woman fills the distance between the
top and bottom of the room. The other woman only fills part of the distance. Thus, the woman on the right appears taller
