Week 2 Object Recognition Flashcards
bottom-up processing
A sequence of events that is governed by the stimulus input itself. Often contrasted with top-down processing.
top-down processing
A sequence of events that is heavily shaped by the knowledge and expectations that the person brings to the situation. Often contrasted with bottom-up processing.
visual search task
An often-used laboratory task in which research participants are asked to search for a specific target (e.g., a shape, or a shape of a certain color) within a field of other stimuli; usually, the researcher is interested in how quickly the participants can locate the target.
tachistoscope
A device that allows the presentation of stimuli for precisely controlled amounts of time, including very brief presentations.
mask
A visual presentation that is used to interrupt the processing of another visual stimulus.
priming
A process through which one input or cue prepares a person for an upcoming input or cue.
repetition priming
A pattern of priming that occurs simply because a stimulus is presented a second time; processing is more efficient on the second presentation.
word-superiority effect
The data pattern in which research participants are more accurate and more efficient in recognizing letters if the letters appear within a word (or a word-like letter string) than they are in recognizing letters appearing in isolation.
well-formedness
A measure of the degree to which a string of symbols (usually letters) conforms to the usual patterns (for letters: the rules of spelling); for example, the nonword “FIKE” is well formed in English, but “IEFK” is not.
feature nets
Systems for recognizing patterns that involve a network of detectors, with detectors for features serving as the initial layer in each system.
activation level
A measure of the current status for a node or detector. Activation level is increased if the node or detector receives the appropriate input from its associated nodes or detectors; activation level will be high if input has been received frequently or recently.
response threshold
The quantity of information or activation needed to trigger a response in a node or detector, or, in a neuroscience context, a response from a neuron.
bigram detectors
Hypothetical units in a recognition system that respond, or fire, whenever a specific letter pair is in view.
local representation
A mode of representation in which information is encoded in a small number of identifiable nodes. Local representations are sometimes spoken of as “one idea per node” or “one content per location.” Often contrasted with distributed representation.
distributed representation
A mode of representing ideas or contents in which there is no one node (or specific group of nodes) representing the content and no one place where the content is stored. Instead, the content is represented via a pattern of simultaneous activity across many nodes within a network. The same nodes will also participate in other patterns, so those nodes will also be part of other distributed representations. Often contrasted with local representation.
inversion effect
a pattern typically observed for faces in which the specific face is much more difficult to recognize if the face is presented upside-down; this effect is part of the evidence indicating that face recongition relies on processes different from those involved in other forms of recongition
excitatory connection
A link from one node, or one detector, to another, such that activation of one node activates the other. Often contrasted with inhibitory connection.
prosopagnosia
A syndrome in which individuals lose their ability to recognize faces and to make other fine-grained discriminations within a highly familiar category, even though their other visual abilities seem intact.
recognition by components (RBC) model
A model of object recognition. In this model, a crucial role is played by geons, the (hypothesized) basic building blocks out of which all the objects we recognize are constructed.
inhibitory connection
A link from one node, or one detector, to another, such that activation of one node decreases the activation level of the other. Often contrasted with excitatory connection.
geons
Basic shapes proposed as the building blocks of all complex three-dimensional forms. Geons take the form of cylinders, cones, blocks, and the like, and they are combined to form “geon assemblies.” These are then combined to produce entire objects.
holistic perception
A process in which the ability to identify an object depends on the whole, or the entire configuration, rather than on an inventory of the object’s parts. In holistic perception, the parts do play a role—but by virtue of creating the patterns that are critical for recognition.
reversible (or ambiguous figure)
Drawings that can be readily perceived in more than one way. Classic examples include the vase/profiles, the duck/rabbit, and the Necker cube.
unconscious inference
The hypothesized steps that perceivers follow in order to take one aspect of the visual scene (e.g., viewing distance) into account in judging another aspect (e.g., size).
shape constancy
The achievement of perceiving the constant shape of objects despite changes in the shape of the retinal image that result from variations in viewing angle.
brightness constancy
The achievement of perceiving the constant brightness of objects despite changes in the light reaching the eye that result from variations in illumination.
size constancy
The achievement of perceiving the constant size of objects despite changes in the size of the retinal image that result from variations in viewing distance.
gestalt principles
A small number of rules that seem to govern how observers organize the visual input, grouping some elements together but perceiving other elements to be independent of one another.
perceptual constancy
The achievement of perceiving the constant properties of objects in the world (e.g., their size, shape, and color) despite changes in the sensory information we receive that are caused by changes in our viewing circumstances.
visual features
The elements of a visual pattern—vertical lines, curves, diagonals, and so on— that, together, form the overall pattern.
figure/ ground organization
The processing step in which the perceiver determines which aspects of the stimulus belong to the central object (or “figure”) and which aspects belong to the background (or “ground”).
necker cube
One of the classic reversible (or ambiguous) figures; the figure is a two-dimensional drawing that can be perceived as a cube viewed from above or as a cube viewed from below.
parallel processing
A system in which many steps are going on at the same time. Usually contrasted with serial processing.
