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Unformatted text preview: 94-100, 104-106The past tense in English•Most verbs form past tense by adding ‘-ed’ to the end of present tense but there are some irregular verbs that can be categorized into 3 classes:oIdentity: they keep same form in present and past (hit/hit)oVowel change: change the vowel (come/came)oArbitrary: (go/went)•Children are correct on irregular past tense, then show overgeneralization, and then eventual correct performance – U shaped effect•Classical theory says that you memorize a list of exceptions in addition to the rule that specifies adding an ‘ex’. Then, successful retrieval of irregular form would block application of the rule. Temporary overgeneralization errors could be cause by still imperfect memory of irregulars•Connectionist models: where present tense presented as input and past tense must be predictedoFirst model: U shaped effect could be obtained by manipulating the type and token frequencies of regular and irregular verb form in accordance with their actual frequencies in spoken EnglishType is a class and a token is an instance of it – ‘ran’ is a type but a particular instance of ‘ran’ is a tokenEnglish verbs are low in type frequency and high in token (there are only few of them and they are used a lot)When training patterns constructed accordingly, along with a gradual expansion of vocabulary, BP networks with hidden units capture the U shaped effectAs learning progressed, many errors see – identity verbs (hit/hit) were often regularized (hit/hitted). Past tense of regular verbs were created by identity (walk/walk), irregular vowel-change verbs were regularized...
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- Fall '10
- neural network