Speaker identification is a challenge for cochlear implant users because their prosthesis restricts access to the cues that underlie natural voice quality. The present thesis examined speaker recognition in the context of spectrally degraded sentences. The listeners of interest were child implant users who were prelingually deaf as well as hearing children and adults who listened to speech via vocoder simulations of implant processing. Study 1 focused on child implant users' identification of a highly salient speaker—the mother (identified as mother)—and unfamiliar speakers varying in age and gender (identified as man, woman, or girl). In a further experiment, children were required to differentiate their mother's voice from the voices of unfamiliar women. Young hearing children were tested on the same tasks and stimuli. Although child implant users performed more poorly than hearing children overall, they successfully differentiated their mother's voice from other voices. In fact, their performance surpassed expectations based on previous studies of child and adult implant users. Even when natural variations in speaking style were reduced, child implant users successfully identified the speakers. The findings imply that person-specific differences in articulatory style contributed to implanted children's successful performance. Study 2 used vocoder simulations of cochlear implant processing to vary the spectral content of sentences produced by the man, woman, and girl from Study 1. The ability of children (5-7 years and 10-12 years) and adults with normal hearing to identify the speakers was affected by the level of spectral degradation and by the gender of the speaker. Female voices were more difficult to identify than was the man's voice, especially for the younger children. In some respects, hearing individuals' identification of degraded voices was poorer than that of child implant users in Study 1. In a further experiment, hearing children and adults were required to provide verbatim repetitions of spectrally degraded sentences. Their performance on this task greatly exceeded their performance on speaker identification at comparable levels of spectral degradation. The present findings underline the importance of ecologically valid materials and methods when assessing speaker identification, especially in children. Moreover, they raise questions about the efficacy of vocoder models for the study of speaker identification in cochlear implant users.

L'activité cérébrale, reliée spécifiquement à la rétention d'information en mémoire à court-terme tactile, a été investiguée à l'aide de l'enregistrement des champs magnétiques produits par l'activité neuronale générée durant la période de rétention par une tâche de mémoire tactile. Une, deux, trois ou quatre positions, sur une possibilité de huit sur les phalangines et les phalangettes, de la main gauche ou droite, lors de blocs d'essai différents, ont été stimulées simultanément. Le patron de stimulation tactile devait être retenu pendant 1800 ms avant d'être comparé avec un patron test qui était, soit identique, soit différent par une seule position. Nos analyses se sont concentrées sur les régions du cerveau qui montraient une augmentation monotone du niveau d'activité soutenu durant la période de rétention pour un nombre croissant de positions à retenir dans le patron de stimulation. Ces régions ont plus de chance de participer à la rétention active de l'information à maintenir en mémoire à court-terme tactile. Le gyrus cingulaire (BA32), le gyrus frontal supérieur droit (BA 8), le precuneus gauche (BA 7, 19), le gyrus postcentral gauche (BA 7), le gyrus precentral droit (BA 6), le gyrus frontal supérieur gauche (BA 6) et le lobule pariétal inférieur droit (BA 40) semblent tous impliqués dans un réseau mnésique qui maintient les informations sensorielles tactiles dans un système de mémoire à court-terme spécialisé pour l'information tactile. / Brain activity specifically related to the maintenance of information held in tactile short-term memory was investigated, using recordings of magnetic fields from a whole-head magnetometer. This neuronal activity was measured during the retention interval of a tactile memory task. One, two, three, or four locations on distal and intermediate phalanges, out of eight positions, were simultaneously stimulated on the left or right hand in different blocks of trials. The tactile stimulation pattern was held in memory for 1800 ms before being compared with a test pattern that was either the same or different by one location. Our analyses focused on regions in the brain that showed a monotonic increase of the sustained activity levels during the retention interval with an increasing number of stimulated locations in the to-be-remembered pattern. These regions are the most likely to participate in the active retention of the information to be held in tactile sensory memory. The right cingular gyrus (BA 32), the right superior frontal gyrus (BA 8), the left precuneus (BA 7, 19), the left postcentral gyrus (BA 7), the right precentral gyrus (BA 6), the left superior frontal gyrus (BA 6) and the right inferior parietal lobule (BA 40) all appear to be involved in a memory system that maintains tactile sensory input in a short-term memory system specialized for tactile information.

Quelle est la nature des représentations que se font les gens des catégories apprises? Il est généralement accepté que le type de tâche d’apprentissage a une influence sur la réponse à cette question. Ceci étant dit, la majorité des théories portant sur les processus de catégorisation élaborées durant les dernières décennies a porté presqu’exclusivement sur des tâches de classifications d’exemplaires. Le mémoire présenté ici avait quatre objectifs principaux. Le premier était de vérifier si une tâche d’apprentissage de catégories implicites par classifications mène davantage à l’intégration de dimensions diagnostiques qu’un apprentissage par inférences. Le deuxième était de vérifier si une tâche d’apprentissage de catégories implicites par inférences entraine davantage l’intégration de dimensions typiques qu’un apprentissage par classifications. Le troisième était d’évaluer si un effet de rehaussement du prototype (« prototype enhancement effect ») pouvait être observé dans le cadre d’un apprentissage par inférences. Le quatrième était de clarifier quelle est la mesure de tendance centrale qui présente réellement un effet de rehaussement du prototype : le mode, la médiane ou la moyenne. Suite aux résultats obtenus, les implications pour trois théories portant sur les processus de catégorisation sont discutées. Les trois théories sont celles des prototypes, des exemplaires et des frontières décisionnelles. / What is the nature of the representations people form of the categories they learn? It is generally accepted that the type of learning task has an influence on the answer to that question. That being said, most of the categorization theories elaborated during the last decades have focused almost exclusively on classification-learning tasks. The master thesis presented here had four objectives. First, to verify if a classification-learning task leads to the integration of more diagnostic dimensions than an inference-learning task in the context of implicit categories. Second, to verify if an inference-learning task leads to the integration of more typical dimensions than a classification-learning task, once again in the context of implicit categories. Third, to evaluate if a prototype enhancement effect can be observed in an inference-learning task. Fourth, to clarify which central tendency measure really presents a prototype enhancement effect: the mode, the median or the mean. Given the results obtained, implications for three categorization theories are discussed. The three theories are prototype theory, exemplar theory and decision-bound theory.

This thesis investigated the testing effect, which is the tendency of testing to enhance learning and memory retention. Specifically, the thesis examines the extent to which test-induced retention benefits extend to the questions as well as the answers; are these benefits symmetrical? The results in the laboratory experiment (Experiment 1) demonstrated that the symmetry in retention benefits is highly dependent on the accuracy in the initial test. For the items students answered correctly in the initial test, the retention benefit was found to be symmetrical across the questions and answers supporting the retrieval hypothesis of the testing effect. However, for initially incorrect items, the retention performance was substantially better for the questions than the answers suggesting an asymmetrical effect from testing, a result that is also consistent with the retrieval hypothesis. These results were replicated using educationally-relevant materials with a delay up to five and a half months in two hybrid studies combining actual classroom experiences with controlled assessments in the laboratory (Experiment 2A & 2B). A series of follow-up studies were conducted to examine the difference in retention performance of the questions and the answers for the initial incorrect items. Particularly, the experiments focused on investigating various factors that might contribute to or eliminate the difference in retention performance, including prior study (Experiment 3), verification feedback (Experiment 4A & 4B) and answer feedback (Experiment 5). The thesis also touched upon various issues related to the temporal dimension of the testing effect. The previous notion that testing slows down forgetting rate is not supported by the data. Instead, testing seems to provide a short-term insulation against immediate forgetting, but then memory for the tested materials decays in the same way as the non-tested materials.

This thesis is divided into three texts. The first is a compendium, which situates the major themes of the second text (a fictitious novel) into a scholarly context and delves into the broader academic questions that arise from it regarding the treatment and care of people with special needs. Those themes are put into a context that enables special education teachers to expand thier notions about communicating with and understanding their autistic and special needs students. It not only examines my own autobiographical connection to the novel (by the fact that I have a sister with a combination of Down Syndrome and autism) but also extends the themes into a broader context, and looks at typical expectations in families with mentally handicapped members and the various methods and approaches of communicating with them. The third text elaborates on specific aspects of these themes in an endnote format.

This thesis is divided into three texts. The first is a compendium, which situates the major themes of the second text (a fictitious novel) into a scholarly context and delves into the broader academic questions that arise from it regarding the treatment and care of people with special needs. Those themes are put into a context that enables special education teachers to expand thier notions about communicating with and understanding their autistic and special needs students. It not only examines my own autobiographical connection to the novel (by the fact that I have a sister with a combination of Down Syndrome and autism) but also extends the themes into a broader context, and looks at typical expectations in families with mentally handicapped members and the various methods and approaches of communicating with them. The third text elaborates on specific aspects of these themes in an endnote format.

Age-related declines in hearing abilities are common and can be attributed to changes in the peripheral and central levels of the auditory system. Although central auditory processing is enhanced in younger musicians, the influence of lifelong musicianship on age-related decline in central auditory processing has not yet been investigated. Therefore, the purpose of this dissertation was to investigate whether lifelong musicianship can mitigate age-related decline in central auditory processing. In the first experiment, age-related declines on four hearing assessments were compared between musicians and non-musicians. Speech-in-noise and gap-detection thresholds were found to decline at a slower rate in musicians, providing an increasing advantage with age. Furthermore, musicians had a lifelong advantage in detecting a mistuned harmonic, although the rate of age-related decline was similar for both musicians and non-musicians. Importantly, there was no significant effect of musicianship on pure-tone thresholds, suggesting that lifelong musicianship can mitigate age-related decline in central but not peripheral auditory processing. To test this hypothesis, a second experiment compared auditory evoked responses (AERs) between groups of older and younger musicians and non-musicians. Results indicated that exogenous neural activity was enhanced in musicians, but that age-related changes were similar between musicians and nonmusicians. Furthermore, endogenous, attention-dependent neural activity was enhanced in older adults, suggesting a compensatory cognitive strategy. Importantly, endogenous activity was preferentially enhanced in older musicians, suggesting that lifelong musicianship enhanced cognitive processes related to auditory perception. In the final experiment, the ability to segregate simultaneous sounds was tested in older and younger musicians and non-musicians by using a mistuned harmonic paradigm, where AERs to harmonic complexes were compared to AERs when one of the harmonics was mistuned. Results indicated that musical training in older adults has little effect on early automatic registration of the mistuned harmonic. In contrast, late attention-dependent activity, associated with the perception of the mistuned harmonic as a separate sound, was influenced by musical training in older adults, suggesting that lifelong musicianship preserves or enhances cognitive components of concurrent sound segregation. In summary, musical training was found to reduce age-related decline in hearing abilities due to enhanced central processing of auditory information.

The dentate gyrus is a region that hosts most of the hippocampal cells in mammals. Nevertheless, its role in spatial memory remains poorly understood, especially in light of the recently-studied phenomenon of adult hippocampal neurogenesis and its possible role in aging and chronic brain disease. We found that chronic over-expression of transforming growth factor beta1 (TGFbeta1), a cytokine involved in neurodegenerative disease, results in several modifications of brain structure, including volumetric changes and persistent astrogliosis. Furthermore, TGFbeta1 over-expression affects the generation of new neurons, leading to an increased number of neurons in the dentate gyrus and deficits in spatial memory acquisition and storage in aged mice. Nonetheless, reducing neurogenesis via pharmacological treatment impairs spatial memory in juvenile mice but not in adult or aged mice. This suggests that the addition of new cells to hippocampal circuitry, and not the increased plasticity of these cells, is the most relevant role of neurogenesis in spatial memory. We tested this idea by modifying proliferation in the dentate gyrus at several ages using multiple techniques and evaluating the incorporation of newborn neurons into hippocampal circuitry. We found that all granule neurons, recently generated or not, have the same probability of being incorporated. Therefore, the number of new neurons participating in memory circuits is proportional to their availability. Our conclusion is that adult-generated cells have the same functional relevance as those generated during development. Together, our data show that the dentate gyrus is important for memory processing and that adult neurogenesis may be relevant to its functionality by optimizing the number of neurons for memory processing. The equilibrium between neurogenesis and optimal dentate gyrus size is disrupted when TGFbeta1 is chronically increased, which occurs in neurodegenerative pathologies, leading to cognitive impairment in aged animals.

A study by Ophir, Nass & Wagner found that younger adults who are heavy media multitaskers (HMM) perform worse on cognitive measures assessing inhibitory control. Previous findings indicated no benefit to being an HMM, however extrapolating from the aging literature wherein older adults can use distraction beneficially, the authors hypothesized that HMMs might show parallel gains. Two tasks (Reading with Distraction, and the Flanker task) are reported with regard to trait media multitasking preference in undergraduates. As expected, LMMs generally outperformed HMMs, but less consistently than predicted. The hypothesis was not proven; media multitaskers, while 4x more likely to recognize the implicit nature of the task, were not more likely to use previously distracting information suggesting that a different mechanism is operating in HMMs than older adults who readily use this information.

Despite years of research in residential energy conservation, means of inducing conservation behaviour through feedback are not well understood. In this thesis I take a novel approach to feedback design by addressing temporal inconsistencies that may hinder individuals from forming an intention to conserve. To help understand conservation compliance strategies, I proposed a visual framework to categorize interventions. I present two design heuristics that were inspired by temporal construal theory (Liberman & Trope, 2003). They were the impetus for the design of three feedback display prototypes, which were examined. Due to methodological limitations, significant improvements to compliance were not found. However, evidence suggests that comparative feedback may have supported reasoning about conservation rather than supporting conservation compliance directly. Future work includes refinement of feedback displays to avoid direct comparisons, exploring the use of nature imagery, and the study of a possible interaction between environmental values and comparative feedback on compliance.