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Psychology notes - Ch5 - Perception
57
Psychology
Undergraduate 1
12/04/2010

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Term
Importance of features
Definition
features play a central role in object recognition
Term
Feature detectors
Definition

neurons in the retina or brain that repsond to specific features of the stimulus (movement, orientation)

 

Term
What do we use  to organize our perception of visual stimuli?
Definition
Interpretation: features, interpretation, organization
Term
Gestalt psychology
Definition
school of pshychology that emphasized organization as an essential feature of all mental activity; emphasizes the role of organized wholes in perception
Term
Parse
Definition
separate a scene into individual objects, linking together the parts of each object that go together
Term
Principles of parsing: list
Definition
similarity, proximity, good continuation, subjective contours
Term
Similarity
Definition

principle of parsing

* principle in perception by which we tend to group  together figures  that resemble each other (blue dots w blue dots)

Term
Proximity
Definition
principle in perception by which we tend to group together figures that are closer together; the closer the figures are to each other, the more we tend to group them together perceptually ( we tend to see kids playing together in groups rather than individual)
Term

Good Continuation

Definition
principle in perception by which we tend to prefer organization in which contours continue smoothly along their original course (leash tangled still looks like one long continuous one rather than many)
Term
 Subjective Contours
Definition
perceived contours that do not exist physically; we tend to complete figures that have gaps in them by perceiving a contour as continuing along its original path; special case of good continuation
Term
 Figure Ground
Definition
separation of the visual field into a part (figure) that stands out against the rest (ground)/ allows you to focus on the figure/ usually the figure is perceived as being closer to the viewer than the background
Term
Reversible Figure
Definition
visual patterns that easily allow more than one interpretation, including figures that allow parsing such that what is initially perceived as figure becomes ground and vice versa
Term
Exampels of reversible figures
Definition
Necker cube, demonstrates that the visual organizaton of the stimulus is not specified by the stimulus itself, but is instead up to the perceiver
Term
Feature Nets
Definition
model of object recognition in which there is a hierarchy of detectors with detectors in each layer serving as the triggers for detection in the next layer/ activation of feature nets can flow from bottom up and top down simultaneously
Term
Bottom up activation of feature nets
Definition
processes move from detection of basic features through more complex detectors; data driven processes
Term
Top down activation of feature nets
Definition
knowledge driven processes guided by the ideas and expectations that the receiver brings to the situation
Term
Irving Biederman. Geons
Definition
primitive 3D geometric figures (cubes, cylinders,  pyramids) from which all other shapes are created through combinations. (30 geons)
Term
Visual Agnosia
Definition
some brain lesions can lead to this disorder, which impairs people's ability to recognize the objects they see; they can describe the object's structures and form, but can't name it or tell its function
Term
Irving Biederman
Definition
In object recognition, the perceiver must first identify its features and then use these features to determine which geons are present. then we use our visual memory to see if there's an object that matches up with what we've detected to determine what the objects are
Term
Problem in object recognition
Definition
visual agnosia
Term
Visual pathway
Definition
signals travel from the rods and cones to bipolar cells to the ganglion cellss which form the opic nerve, leaves the eyeball and travels to the brain
Term
Ganglion cells can be classified into 2 categ:
Definition
parvo and magno cells
Term
Parvo cells
Definition
smaller cells that blanket the entire retina; outnumber the magno cells; senstitive to hue and brightness differences; play a crucial role in perception of pattern and form
Term
Magno cells
Definition
larger cells found primarly in the retina's periphery; insensitive to hue differences but respond strongly to changes in brightness; play a central role in detection of motion and perception of depth
Term
Single cell recording technique
Definition
evidence for neural specializatio comes from single cell recording techniques - determine which specoific stimuli elicit a response from a cell and which don't
Term
Parallel processing in the Visual Cortex
Definition

=different cells and areas of the brain specialize in a particular kind of analysis, and these different analyses go on in parallel - some cells are analyzing form, other motion, color, etc

a) allow for greater speed

b) allows each system to draw info from the others and to help and influence each other

c) explains how feature detection depends on interpretation, and vice versa; ensures that our perception makes sense at both the larger scale and fine grained levels

Term
The "what" and "where" systems
Definition
in the inferotemporal cortex and parietal cortex
Term
"What" system
Definition

-occipital temporal pathway

- system of visual circuits and pathways leading from the visual cortex to inferotemporal cortex (temporal lobe); especially involved in object identification (i see a pen)

- damage leads to visual agnosia- unable to recognize visual objects and faces

Term
"Where" system
Definition

- occipital parietal pathway

- system of visual circuits and pathways leading from viaul cortex to parietal lobe

involved in spacial localization of objects and coordination of movement (pencil's lying to my right and i moved my hand to reach it)

- damage leads to having difficulty with visual orientation and reaching for objects but no problem identifying them

Term
Binding problem
Definition
how the nervous system manages to bind together elements that were initially detected by separate systems
Term
Neural synchrony
Definition

= different groups of neurons firing in synchrony with each other; brain uses these patterns to identify which sensory elements belong with witch

a) uses the timing of the firing by these groups of neurons if the neurons are firing at the same time, seems to indicate that the messages from the neurons are bound together

b) for ex, if neurons detecting a vertical line are firing at the same time as the neurons signaling movement, then these attributes are registered as belonging to the same object

- if the neurons aren't firing together, the features are registered as belonging to separate objects

Term
Perceptual constancy
Definition
size, shape, brightness
Term
 Perceptual constancy
Definition
the constant attributes of a distal object (size shape) that we are able to perceive despite differences in the proximal stimulus; we perceive the constant properties of objects, even though the sensory information we receive about these attributes changes whenever our viewing circumstances change
Term
Size constancy
Definition
the tendency to perceive objects as retaining their shapes, despite the increase or decrease in the size of the  image projected on the retina by moving closer to or farther from the objects
Term
Shape constancy
Definition
the tendency we perceive objects as retaining their shapes, despite changes in our viewing angle that produce changes in the image projected on the retina
Term
Brightness constancy
Definition
the capacity to perceive an object as having an unchanging brightness, despite the fact that changes in illumination cause a change in how much light refelcts off the object and reaches the eye
Term
Unconscious inference
Definition

these perceptual constancies seem to be achieved by making inferences unconsciously, taking our viewing circumstances into account in a way that allows us to perceive the constant properties of the visual world

* process proposed by Helmholtz to explain how we accomplish size constancy by using distance calculation w/o consciously doing so

Term
How is size constancy achieved?
Definition

a) unchaging relationships: relationships between size within retinal image stay the same as we move closer or farther away

b) distance info - Helmholtz inverse relat b/in distance and retinal image size: size of image * distance

Term
Distance cues
Definition

= features of the stimulus that indicate an object's position; sources of info that signal the distance from the observer to the distal stimulus

- binocular and monocular cues

Term
Binocular cues
Definition

cues for distance that involve using both eyes

- binocular disparity (3D movies)

Term
Monocular cues
Definition

cues for distance that only involve using one eye

- pictorial cues - used by artists to create an impression of depth on a flat surface

- interposition and linear perspective

Term
Interposition
Definition
Monocular distance cue  in which an object that is blocked by another object is viewed as farther away  than the object that's blocking our view of it
Term
Linear Perspective
Definition
a monocular cue for distance in which parallel lines seem to converge as they get farther and farther away from the viewer; this cue is based on the fact about optics that distant objects produce a smaller retinal image than do nearby objects of the same size
Term
Motion parallax
Definition
depth cue provided by the fact that as an observer moves, the images cast by nearby objects move more rapidly on the retina than images cast by objects that are farther away
Term

Optic flow

Definition
a depth cue provided by the fact that, as an observer approaces an object, the object's retinal images enlarges, whereas when an observer retereats from the objects, the retinal image of the object shrinks; this cue gives us crucial info about depth and plays a large role in coordination of our movements
Term
Role of redundancy
Definition

different distance cues become important in different circumstances, for example:

a) binocular disparity is used when objects are relatively close (closer than 30ft)

b) motion parallax and optic flow are used only when we're moving

c) texture gradients are used only if there's an uniform texture in view

Term
Motion detectors
Definition
cells in the visual cortex that are sensitive to an image moving across the retina; these cells are direction specific
Term
Direction specific
Definition
motion detectors in the visual cortex fire if a stimulus moves across their receptive field from a particular direction only; other motion detector cells fire if the motion is from another direction
Term
Apparent movement
Definition
perception of movement by stimuli that are stationary but flash on and off at apropriate positions and at appropriate time intervals; can be indistinguishable from real movement (movies)
Term
Position constancy
Definition
we perceive an object as having an unchanging position in space, despite the fact that changes in the viewer's position cause a change in the spatial position of the retinal image cast by the object
Term
Cancelling out theory
Definition
the theory that explains the position constancy-it states that we take our own movements into account by computing the shift in the retinal image that our own motion will produce and cancelling out the amount of movement in interpreting the visual input; we can compare the anticipated shit due to our movements with the shift that actually occurs- if they match, then all movement is due to our movement and there's no movement in the environment
Term

Induced motion

Definition
movement is perceived in a stationary stimulus that's enclosed by a moving framework
Term
Correspondence problem
Definition
in a moving display, a pattern in which surrounding objects are in fact moving but are perceived as stationary, and in which the self (not moving) is perceived as moving
Term
How do we pay attention to some inputs but not to others?
Definition
orienting, conjunction search, priming
Term
Orienting
Definition
tendency of an organism to shift its attention and sensory machinery (turn heads, etc) to inspect a novel, unexpected, or otherwise interesting stimulus; there are physical adjustments in selecting what we pay attention to, which includes moving parts of our body to better perceive the stimulus
Term
Conjunction search
Definition
search in which the target is defined by a combination of features, such as looking for a red circle among a display of red verticals and yellow circles; involves mental adjustments in selecting what we pay attention to
Term
Priming
Definition
a warming up of certain detectors so they're better prepared to respond than they otherwise would be; helps to focus our attention and avoid distracters, but may hinder our perception of anything else; seems to influence how we allocate our rpcessomg resources affecting our internal selection process
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