The hippocampus plays a critical role in binding together information into an integrated memory, and memory for these arbitrary associations is important when learning new words. Recent studies have investigated a learning mechanism called fast mapping (FM), showing that rapid acquisition of novel arbitrary associations can be learned independent of the hippocampus. In the current study we examine word-learning across two conditions more and less likely to require information integration via the hippocampus in typically developing children and individuals with hippocampal dysfunction (e.g., Down syndrome). Individuals with Down syndrome (DS) manifest hippocampal dysfunction and display memory and learning difficulties, hence could potentially benefit from alternative learning strategies. The current study found no benefit of the FM condition in either group. Both groups performed similarly and above chance level across the two conditions and over a week's delay, but a delay by group interaction suggested that the typically developing children showed improvement across all conditions after 1 week whereas performance in DS stayed consistent. Given evidence for sleep deficits in DS we examined how sleep disturbance related to delayed word retention. Sleep efficiency did not appear to be driving maintenance in either group. Future studies investigating when an individual with DS sleeps after learning, could provide a better understanding of how sleep can influence the word learning process. Additionally, future studies in an older group of children can also provide information on when the hippocampus and sleep dependent learning may develop in childhood.

In order to learn a new word, a young child must extricate the correct object from multiple possible items in front of them, make an initial association between the specific word-form and the particular referent, robustly link the new word and referent and integrate the new word into their lexicon. Recent research suggests processes that focus attention on the most novel objects in a complex environment, as well as the child's own developing vocabulary play critical roles in this process. This thesis aims to understand the influence of novelty and prior vocabulary knowledge on referent selection and how the interaction of novelty and knowledge can lead to word learning. A series of empirical studies first probed the use of children's endogenous novelty bias in a referent selection task, and then explored how the use of novelty was related to retention of newly mapped word-referent pairs. A second set of studies explored children's use of vocabulary knowledge in ambiguous learning situations by varying the strength of knowledge for competing items present during novel word learning. Finally, a Hebbian Normalized Recurrent Network model was used to explore the underlying associative process of referent selection and retention in novelty- or knowledge-based word learning tasks. Counter to prior work, results here suggest that novelty can override knowledge and in fact, be a detriment to word learning. Children demonstrate a novelty bias across multiple contexts and tasks, but the dominant use of novelty does not translate to retention and does not appear to implicate the use of the child's lexicon. As novelty diminishes and vocabulary knowledge increases, some children can overcome this bias and demonstrate retention for new word-referent pairs. Moreover, the results also suggest that when disambiguation requires the use of weak prior knowledge, more cognitive processing is necessary. The increases in processing subsequently translate to retention for new word-referent pairs. The empirical and computational results together suggest potential limitations of these findings to word learning and suggest future directions exploring variability in object and word representations during learning.

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Made available in DSpace on 2016-06-02T20:30:55Z (GMT). No. of bitstreams: 1 5022.pdf: 1889377 bytes, checksum: f804286a43c335f751c6d1742038211b (MD5) Previous issue date: 2013-02-25 / Universidade Federal de Minas Gerais / Exclusion responding has been considered one of the processes by which children learn to relate new words to objects. This pattern of responding is usually tested with a matching to sample task. The goal of the present experiment was to verify if exclusion responding also occurs with properties-object relations: dictated model stimuli were adjectives (/happy/, /sad/ and /anger/) and comparison stimuli were properties of objects (dolls facial expression). A second goal was to investigate the relation between the quantity of exclusion trials and a learning outcome. Phase 1 established a baseline of auditory-visual discriminations in a natural situation with dolls; Phase 2 established the baseline among dictated words and pictures of the doll (a girl) with a specific software presented with a notebook; Phase 3 consisted of exclusion probes in which the pseudo words /piva/ and /fobam/ were presented as models in different trials and a defined face (related to baseline words), an undefined face (not related to baseline words) and a mask (blank comparison) were presented as comparison. Selection of undefined face showed exclusion control. Phase 3 also consisted of presentation of learning probes. In Phase 4 experimental blocks presented as comparison stimuli figures of another doll (boy) expressing the same emotions of the doll of Phase 3. The purpose of Phase 4 was to evaluate generalization of the results obtained in Phase 3. Experiment was finished if the participant had responded correctly the three learning probes or if he or she had been exposed to 10 exclusion trials with each relation. Data was collected with 22 typically developing preschool children between 24 and 29 months of age. All participants responded by exclusion along the experiment. 11 of the 22 participants showed a learning outcome, responding correctly the three learning probes (100% of correct responses) with one of the taught relations in Phase 3 or with one of the tested relations in Phase 4. Data confirm and extend regularity of exclusion responding. The amount of exclusion trials necessary to obtain a learning outcome and the best learning probes to be used still needs to be investigated. / O responder por exclusão é considerado um dos processos pelos quais as crianças aprendem a relacionar palavras novas a objetos. A tarefa experimental típica é a de escolha de acordo com o modelo. Este estudo teve como objetivo verificar se o responder por exclusão ocorre no ensino de relações palavra-qualidade (adjetivos): os estímulos modelo ditados eram adjetivos (/feliz/, /triste/, /brava/) e os estímulos de comparação visuais eram faces estilizadas de um fantoche. Verificou-se também a relação entre a quantidade de tentativas de exclusão e a aprendizagem de novas relações palavra-qualidade. A Fase 1 consistiu no estabelecimento da linha de base de discriminações auditivo-visuais em uma situação natural. Na Fase 2, a linha de base foi estabelecida em um computador portátil. A Fase 3 consistiu na apresentação de tentativas de exclusão em que duas pseudopalavras /piva/ e /fobam/ eram ditadas como modelos em diferentes tentativas. Os estímulos de comparação eram uma face definida (relacionada à linha de base), uma face indefinida (não relacionada à linha de base) e um estímulo comparação vazio (máscara). A seleção da face indefinida evidenciaria o controle por exclusão. Durante a Fase 3 foram apresentadas também sondas de aprendizagem. Na Fase 4, os blocos experimentais apresentavam como estímulos de comparação bonecos do sexo masculino com as mesmas expressões faciais das do fantoche da Fase 3. Essa fase teve como objetivo verificar a generalização do padrão comportamental dos participantes na fase anterior. O procedimento era finalizado caso o participante acertasse as três sondas de aprendizagem ou após o máximo de 10 tentativas de exclusão com cada relação. Os participantes, 22 crianças pré-escolares, com desenvolvimento típico e idades entre 24 e 29 meses, responderam por exclusão em praticamente todas as sondas ao longo do experimento. Desses, 11 apresentaram desempenho correspondente com aprendizagem em pelo menos uma das novas relações ensinadas na Fase 3 e avaliadas na Fase 4. Os dados confirmam e estendem a regularidade do responder por exclusão. A quantidade de exposição a tentativas de exclusão necessárias para assegurar aprendizagem e a validade dos tipos de sondas de aprendizagem ainda devem ser verificadas experimentalmente.

Chez les enfants souffrant de troubles spécifiques du langage oral (TSLO), des déficits demémoire à court terme verbale et d’acquisition lexicale sont fréquemment décrits. Ces capacités sont évaluées par des tâches de répétition et plus généralement de production verbale, mettant en jeu demultiples composants susceptibles d’être altérés dans les TSLO. Dans ce contexte, l’objectif généralde cette thèse était l’examen de mécanismes de mémorisation verbale à l’aide du paradigme dumonde visuel. L’oculométrie consiste à analyser les mouvements oculaires des participants sur desimages, à la suite de stimulations verbales. La reconnaissance et la mémorisation à court terme demots parlés familiers ont été examinées à travers quatre études, auxquelles les participants avec etsans TSLO âgés de 5 et 6 ans, ont obtenu des résultats comparables. Seules des différences enfonction de l’âge ont été révélées, reflétant les changements développementaux du traitement lexical.Dans un second temps, le paradigme d’appariement rapide pour l’acquisition de nouveaux mots(« fast mapping »), nécessitant peu de présentations, a été proposé à trois groupes d’enfants. Leurscapacités d’acquisition lexicale ont à nouveau été évaluées via le paradigme du monde visuel à unetâche de reconnaissance de mots parlés. Les groupes TSLO présentant des déficits en répétitionverbale, ont néanmoins reconnu et apparié les nouvelles étiquettes lexicales aux images référentes,comme leurs pairs au développement typique. Les études menées ont permis de mettre en évidenceque le maintien à court terme de l'information verbale ainsi que l’encodage de nouvelles informationssont efficients chez les enfants avec TSLO, lorsque la production verbale n’est pas sollicitée. / In children suffering from specific language impairment (SLI), verbal short term memory disorders and lexical learning inability are frequently described. These skills are assessed through repetition tasks and more generally, with verbal output modality which variety of components can be impaired in SLI. In this context, the general aim of this research work was the examination of verbal memorization processes through visual world paradigm. This eye-tracking tasks consist in analyzing eye movements of participants on pictures, consecutively to verbal stimulations. Recognition and short term retention of familiar spoken words were investigated through four studies, in which participants aged 5 and 6, with and without SLI, shown similar patterns of result. Only age differences were revealed, suggesting developmental changing of lexical processing. In a second phase, the fast mapping word learning paradigm requiring few occurences of new words, was proposed to three groups of children. Their lexical learning abilities were again assessed within the visual world paradigm and a spoken word recognition task. SLI groups with poor performances in verbal repetition tasks, have nevertheless associated the new lexical label with referent picture, as their peers with typical development. These studies suggest that verbal information retention in short term memory and encoding of new information are efficient in SLI children, when the tasks do not require any verbal output.