click below
click below
Normal Size Small Size show me how
Semantic Networks
Lecture 13 & McClelland Reading
Question | Answer |
---|---|
semantic tasks are | those that require a subject to produce/verify semantic info about an object, a depiction of an object, or a set of objects indicated verbally by a word |
semantic info is | info that has not previously been associated with the particular stimulus object itself & which is not available more-or-less directly from perceptual input provided by the object/object description |
semantic task performance is thought to depend on a mediating process of categorization where there exists | a representation in memory corresponding to each of many concepts/categories & info about the concepts is either stored in the representations or is only accessible from it |
within model performance on semantic tasks depends on | access to relevant category representations |
categorization based approaches lie | implicitly/explicitly at the base of theorizing about semantic knowledge & its use in semantic tasks |
the 3 constructs that are frequently invoked in categorization based theories to explain empirical data are | hierarchical structure, privilege categories, category prototypes |
hierarchical structure.. | directs the sharing of info across related concepts at different levels of abstraction |
privileged categories contain | info that is accessed directly & not by means of spreading activation in the processing hierarchy |
category prototypes are | the means of computing similarity between individual instances & stored category representations |
the 3 constructs used in categorization based theories offer | an incomplete & in some ways paradoxical basis for accounting for relevant empirical phenomena |
for many natural domains there exists constraints on category membership | such that exemplars of one category must also be members of another & these class inclusion constraints can be described by a taxonomic hierarchy |
Quillian pointed out that a taxonomic hierarchy can provide an efficient mechanism for storying/retrieving semantic info with the key aspect being | the observation that category membership at each level entails a # of properties that are shared by the members of the more specific included categories |
Quillian proposed a spreading activation mechanism that | permitted the activation of a category representation to spread to taxonomically superordinate concepts & this model provided a mechanism for property inheritance & generalization of new knowledge |
the time it takes to verify category membership at various levels can often | violate the predictions of the taxonomic hierarchy model |
in neuropsychology Warrington accounts for | pattern of deficits in cases of progressing fluent aphasia or semantic dementia |
semantic dementia of fluent aphasia is | the progressive deterioration of semantic knowledge while other cognitive faculties remain relatively spared |
in semantic dementia what info is lost earlier in the progression of the disease? | info about specific categories at the bottom of the taxonomy |
studies by Cambridge group show that semantic dementia patients exhibit | relatively preserved general knowledge in a variety of semantic tasks |
the structure apparent in impair performance of semantic tasks reveals | the organizational structure of concepts in memory |
warrington suggested that categories located and the top of taxonomy are | the first to be activated during access & the first to be acquired in development |
Neil used children's responses to the judgement or propositions & their negations to construct predictability trees which | describe children's ontological distinctions |
concepts on predictability trees occupy the same node if | they can reasonably enter into same set of propositions |
the taxonomic structure is used to explain the | influence of general category membership on the processing of more specific category info |
info stored with more general representations can determine | the feature weights for more specific categorizations but the hypothesis doesn't explain why a given feature is important for some categories & not others or how the relevant knowledge was acquired in the 1st place |
illusory correlations are | a way general knowledge may influence the processing of more specific info |
studies show that people are not good at estimating | the frequency objects & properties co-occur across a particular set of events |
subjects persist in the belief that particular objects/properties have occurred together frequently even with | contrasting evidence & may discount/ignore co-occurrence of object-property pairs during learning |
children in Massey & German's experiment are able to | categorize objects at general level of animate/inanimate & attributed typical properties to unfamiliar stimuli |
2nd major influence on categorization based theories of semantic task performance stems from studies on | basic level of categorization |
subjects often perform best in semantic tasks requiring them to | identify objects at basic level |
Roach et al. demonstrated that at the basic level subjects | fastest to verify membership prefer to use the basic label in pic-naming tasks fastest to discriminate objects at the basic level show a larger effect of visual priming to basic level children first learn to name objects w/ their basic-level name |
basic-level advantages are observed because | the cognitive system exploits representations that correspond to into-rich bundles of co-occurring attributes in the environment |
basic categories tend to have | special statistical properties |
Murphy & Lassaline describe basic categories as | maximizing informativeness & distinctiveness |
more general categories are not very informative because | their exemplars have little in common |
more specific categories are informative but not particularly distinctive because | they have few distinguishing characteristics |
objects from same basis category tend to | share many properties with each other& few with contrasting categories & are considered to be particularly useful |
Rosch proposed that cognitive faculties develop to take advantage of the basic level structure by | forming summary representations of maximally listing & informative categories of objects |
what constitutes the basic level reflects | shared/distinctive properties as these are known within a particular culture |
the basic level has advantage for | typical members but not atypical |
"basic level" concept representations constitute the | entry point into a taxonomic processing hierarchy |
a given stimulus directly activates | only its basic category representation |
info stored at other levels of abstraction | must be retrieved by means of spreading activation in the taxonomy |
privileged access theories introduce | a distinction between semantic info retrieved directly by means of categorization & indirectly through reference to stored class-inclusion links |
basic-level phenomena are observed because | info stored at more general/specific levels of abstraction is only accessible through the prior activation of base-level concept representations |
Jolicoeur et al. stipulated that entry-level categories don't need to | reside at same level of taxonomic specificity for all exemplars & might be found at a more specific level of the hierarchy for atypical instances |
basic-level advantages can shift with | increasing expertise in a domain which suggests that such effects are in part constrained by experience |
experts prefer to name at the | subordinate level in their domain & novices prefer to name at basic-level |
experts in a given domain may derive somewhat different conceptions about how | items in the domain are similar to one another depending upon the kind of expertise they have acquired |
the processes by which we construct semantic representations are sensitive to | the details of the experience we have within the categories |
evidence that a level of category structure intermediate between between the most specific & most general has | primacy over the most general level |
Roach argued natural categories have a tendency to share | family resemblances |
attributes have a tendency to | occur in clusters |
the cognitive system exploits such discontinuities by | forming summary representations of categories that correspond to clusters of correlated attributes in the environment |
membership in most natural categories is | graded (some objects are better examples of categories than others) |
poor/atypical members of a category take longer to | verify than good/typical members |
Roach & Mervis: semantic system may store summary category representations as | a prototypical set of descriptors that are generally, but not necessarily, true of the category's exemplars |
time taken to classify a given instances is inversely proportional to | the # of attributes it shares with a prototypical category members |
prototype theory | natural categories are represented by summary descriptions that are abstracted through exposure to instances in the environment |
novel instances are compared to stored summary descriptions & are assigned to | the category with the closest match under some measure of similarity |
in prototypes theory the time taken to perform assignment depends upon | feature overlap between novel instance, correct category, & competing categories |
Mervis extended prototype theory to account for | data from lexical acquisition |
child-basic category prototypes include | a small # of properties relative to adult category prototypes |
category prototype representations may be used to explain | effect of typicality on reaction times in category & property-verification tasks over-extension of familiar names to inappropriate but related objects in lexical acquisition & dementia & inappropriate restriction during early word learning |
similarity-based models that attempt to do away with taxonomic processing structure will have difficulty explaining | how more general category membership can influence categorization processing at more specific levels |
hierarchically organized processing models will have difficulty explaining | the strong influence of typicality on semantic judgements |
categorization-based theories face further challenges from | the theory-theory approach |
basic tenet of theory-theory approach is that | semantic cognition is constrained to a large extent by the naive domain knowledge ( a "theory") that people hold about casual relations that exist between entities in a domain |
it is difficult to characterize just what | "nice theories" are |
the key function of the theory-theory approach is to | explain/predict observed events in the environment & it serves this function with reference to stored knowledge about the casual properties of & relations between objects |
in the TLC model a node inherits | the properties of its "parents" and "grandparents" |
the TLC model cannot account for | reverse distance effects typicality effects basic level effects |
the original TLC model is hierarchical with all links the same length while the revised TLC model is | not s strict hierarchy because concepts can be associated via a direct link & connections vary in length |
in the revised TLC model the length of the link corresponds to | the strength of the relationship |
properties in the original TLC are given by | walking up the links to inherit the properties |
in the revised TLC model the properties are inherited by | spreading activation |
being semantically primed means that | a person is faster to respond to a lexical decision task if it was preceded by a related word |