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Tracking the identity of occluded objects requires binding an object’s features to its location to represent exactly which objects are located where, relying heavily on capacity-limited visual working memory. This dissertation aims to examine the capacity and stability of object working memory, and the complexity and fidelity of object working memory representations, in toddlers and young children. A series of four experiments used a novel task to examine 28- to 40-month-old toddlers’ and 5- to 6-year-old children’s visual working memory recall of specific objects in specific locations. I predicted capacity limits would vary with age, presentation/occlusion type, and complexity, and that older children would be able to monitor these limits successfully. Children observed arrays of featurally-distinct objects that were hidden from view either simultaneously (Chapter 2, Experiment 1 and Chapter 3, Experiments 1 & 2) or sequentially (Chapter 2, Experiment 2) and were asked to recall an object’s location. When objects were hidden simultaneously, toddlers showed a capacity of 3 feature-location bindings (Chapter 2, Experiment 1) and 5- to 6-year-old children showed a capacity of 4 feature-location bindings (Chapter 3, Experiment 1), and both showed capacity development, supporting the hypotheses. When objects were hidden sequentially, toddlers’ performance was impacted by whether they had the easier (set size 2) or harder (set size 3) block first, suggesting the structure of the task may have influenced how children divided attention between maintaining and encoding of representations in working memory. Additionally, in Chapter 3, the number of feature bindings that children had to maintain was varied. Children could remember more single-feature objects than multi-feature objects (limit of 4 vs. 3, respectively), suggesting that binding additional features to a representation taxes cognitive resources, as hypothesized. Finally, the study in Chapter 3 explored children’s ability to monitor the fidelity of their visual working memories by asking them to gauge their confidence by placing bets with tangible, at-risk resources. Children modulated their bets appropriately, betting more after providing correct answers and fewer after incorrect answers, as hypothesized. Together, these data help to inform our understanding of visual working memory for feature-location bound objects across early development.

No description available.

Edublox is an educational training facility with headquarters in Pretoria, with branches nationally and their programme marketing internationally. Their latest development was the Edublox Online Tutor (EOT) programme that claims to enhance cognitive functioning in children. This retrospective study thus seeks to establish whether exposure to the EOT programme has an impact on the cognitive functioning (specifically working memory - comprising of visual working memory, auditory memory, and logical reasoning) of primary school children. The conceptual structure for this study was formed using The Cognitive Information Processing Theory and Vygotsky’s Social Cognitive Theory. A convenience sampling method was chosen and comprised of grade 2 children (n=64) who formed 3 groups; 2 experimental groups (EOT and educational computer games) and a control group (usual schooling). A quantitative, experimental research design was adopted throughout the study and included pre-and post-assessments of cognitive performances. Varying data analysis techniques, such as mean plots, paired samples t-tests, and one-way repeated measures ANOVA tests were utilised. Overall, analyses revealed that exposure to the EOT programme significantly improved children's conceptual skills in one out of the 4 variables tested in cognitive performance. Other findings revealed that while there were overall improvements in mean post-test scores, there were no significant differences in mean post-test scores between the experimental groups and the control group. The differences in strength of changes between the pre-and post-test scores were influenced by the length of exposure, the type of intervention, the delivery environment, and the sample size, among other factors. It was recommended that the treatment period is lengthened, a multimodal approach is adopted, and the treatment environment is varied to investigate effect sizes and enhance the validity and comparability of this study. / Dissertation (MA (Research Psychology))--University of Pretoria, 2020. / Psychology / MA (Research Psychology) / Unrestricted

This study seeks insight into the use of visual aids in contemporary post-compulsory teaching. The importance of the study is linked to the large number of students who enter Higher Education; many of whom regularly receive lectures supported by visual displays which comprise textual summaries of a lecturer’s speech. This thesis comprises a two-part study and employs a mixed methods approach. The first part inquires into teachers’ and lecturers’ practice with regard to their visual aids, and the second compares the effectiveness of text, images and imagery displayed in support of a lecture. The investigation into lecturers’ practice found many post-compulsory teachers and lecturers had received no training in the design and use of visual aids during their initial teacher training. It is suggested this privation may underpin a de facto choice of projected text as a visual aid, the use of which is not clearly supported by contemporary models of memory and mental processing. In a comparison of visual modalities, an increase in learner engagement was recorded for the display of carefully designed images, and also for directed imagery. No positive impact was recorded for text summaries of 50-64 words displayed concurrently with speech, although recall was improved when text was restricted to five words or fewer. The conclusion is drawn that the display of this modality without temporal pauses may offer limited educational advantage to students, and a method of planned apportionment of speech and text is proposed in which contemporary theories of memory and processing are taken into account. These observations have significant implications for a lecture environment in which such text summaries are often relied upon for visual support. The findings of the thesis are combined to propose a principle of Visual Working Memory Utilisation (VWMU), upon which future research into visual aid design and use in post compulsory education might be based.

Le processus de vieillissement humain est un processus complexe qui varie grandement d’une personne à l’autre. Malgré l’ampleur des recherches faites sur le sujet, il reste encore beaucoup à explorer et à comprendre. Cette thèse propose trois expériences qui nous permettent d’améliorer notre compréhension des changements qui s’opèrent dans la mémoire de travail visuelle et l’attention visuospatiale avec la prise en âge. La première expérience propose d’examiner les changements dans les capacités de mémoire de travail visuelle entre des jeunes adultes, des adultes âgés sains et des personnes atteintes de trouble cognitif léger (TCL). De plus, grâce à un suivi fait avec les personnes ayant un TCL, nous avons pu examiner si des différences existaient au niveau comportemental entre les âgés qui ont déclinés vers un type de démence et ceux dont l’état est resté stable. Plusieurs techniques peuvent être utilisées pour étudier les effets du vieillissement sur le cerveau. Les tests neuropsychologiques et les tâches comportementales présentées dans la première expérience en sont un exemple. La neuroimagerie peut aussi s’avérer particulièrement utile. En effet, certaines mesures électrophysiologiques, aussi appelées potentiels reliés aux évènements (PRE), sont associées à des fonctions cognitives précises. Ces composantes nous permettent de suivre ces processus et d’observer les modulations causées par les caractéristiques des stimuli ou l’âge par exemple. C’est le cas de la N2pc (négativité 2 postérieure controlatérale) et de la SPCN (sustained posterior contralateral negativity), des composantes électrophysiologiques liées respectivement à l’attention visuospatiale et la mémoire de travail visuelle. On connait bien ces deux composantes ainsi que les facteurs qui les modulent, or elles sont peu utilisées pour les changements qui occurrent dans l’attention et la mémoire de travail visuelle dans le cadre du processus de vieillissement. Les deuxième et troisième expériences proposent d’utiliser une tâche de recherche visuelle (nombre d’items de couleur et identification d’une relation spatiale entre deux items de couleur) afin d’explorer les changements observables sur ces composantes électrophysiologiques. La deuxième expérience examine l’efficacité d’un paradigme à présentations multiples (‘multiple frame’) afin de mesurer la N2pc et la SPCN chez de jeunes adultes. La troisième expérience a pour but d’examiner les effets du vieillissement normal sur l’amplitude et la latence de la N2pc et la SPCN en utilisant le même type de tâche de recherche visuelle. / Human ageing is a complex process that varies a lot from one person to the other. Despite the scope of research of that subject, there is still a lot to explore. This thesis proposes three experiments that will help increase our understanding of the many changes in visual working memory and visuospatial attention seen in ageing. The first experiment assesses the changes in visual working memory capacities between young adults, healthy older adults, and persons with MCI. Furthermore, we were able to do a follow-up with the persons with MCI and determine which ones remained in a stable cognitive state and the ones that decline toward mild dementia, providing us with the opportunity to test for potential behavioral differences allowing us to distinguish between them. Many techniques, such as neuropsychological tests and behavioral tasks, can be used to study the effects of ageing on the brain. Neuroimaging techniques can be particularly useful. In fact, many electrophysiological measures, called event-related potentials (ERPs), are linked to specific cognitive functions which allow us to follow those processes and observe the modulations caused by stimuli characteristics or ageing for example. This is the case of the N2pc (negativity 2 posterior contralateral) and the SPCN (sustained posterior contralateral negativity), two ERPs linked to visuospatial attention and visual working memory. While they are both well-known in the literature, not many studies are using them as a way to examine the changes appearing in the visuospatial attention and the visual working memory during the normal ageing process. The second and third experiment use a visual search task (including 2 conditions: counting the number of items presented and identify a specific spatial relation between 2 coloured items) to explore the changes seen on those ERPs. The second experiment wants to assess the efficiency of a multiple frame paradigm to measure the N2pc and the SPCN with young adults. The third experiment wants to examine the effects of normal ageing on the amplitude and the latency of the two components using the same type of visual search task.

Les potentiels reliés aux événements (PRÉ) sont très couramment utilisés comme méthode de mesure de l’attention visuelle. Certaines composantes PRÉ comme la N2pc et la P3 sont largement considérées comme marqueurs du déploiement de l’attention. Afin d’investiguer s’il est possible de déterminer la localisation sur laquelle l’attention est dirigée ou encore la présence ou non de l’attention à une localisation donnée, une tâche d’indiçage spatial a été utilisée. L’indice indiquait l’une de quatre localisations sur laquelle les participants devaient diriger leur attention. L’indice spatial utilisé était de nature exclusivement symbolique, impliquant que l’attention devait être déplacée de façon volontaire. L’analyse des signaux ÉEG captés alors que les participants réalisaient la tâche a été effectuée en faisant usage d’une technique d’apprentissage machine. Un classificateur de type SVM (Support Vector Machine) a ainsi été utilisé afin de prédire la présence ou l’absence d’attention à une localisation en utilisant le signal ÉEG associé aux cibles et aux distracteurs. Un taux de précision de 75% (p < 0,001) a été obtenu lors de cette classification, le niveau du hasard se trouvant à 50%. Un classificateur de type DSVM (SVM à dendrogramme) a été utilisé afin de prédire le locus précis de l’attention en utilisant le signal ÉEG relié aux cibles uniquement. Dans ce problème de classification, un taux de prédiction exacte de 51,7% (p < 0,001) a été obtenu, le niveau du hasard étant de 25%. Les résultats indiquent qu’il est possible de distinguer le locus attentionnel à partir des PRÉ dans un espace de +/- 0,4 degrés d’angle visuel et ce, avec des taux de précision dépassant largement le niveau du hasard. / Event related potentials (ERP) are commonly used as a method of measuring visual attention. ERP components such as N2pc and P3 are largely considered as markers of attention deployment. In order to investigate the possibility of predicting the locus and the presence or absence of attention, a spatial cueing task was used. A cue indicated one of the four locations on which subjects had to direct their attention. The spatial cue was exclusively symbolic, implying that attention had to be oriented voluntarily. The analysis of the EEG signal which was measured as subjects carried out the task was performed using machine learning. An SVM (Support Vector Machine) classifier was used to predict the presence or absence of attention at one location, using the EEG signal associated with targets and distractors. A decoding accuracy of 75% (p < 0,001) was achieved for this classification, with a chance level of 50%. A DSVM (Dendrogram SVM) was used to predict the precise locus of attention using the EEG signal linked to targets only. In this classification problem, a decoding accuracy of 51,7% (p < 0,001) was achieved, with a chance level of 25%. These results suggest that it is possible to distinguish the locus of attention from ERPs in a +/- 0,4 degrees of visual angle space with decoding accuracies considerably above chance.

A standard Neurofeedback approach to mitigate the working memory decline in some fragile groups (elderly, subjects affected by stroke or Alzheimer's disease) can be suboptimal for some patients. The goal of this research is to investigate which visual stimulus (among colour, geometrical shape, direction, and symbol) is the most suited for each of the six healthy participants and which brain areas are the most discriminative, during the maintenance of a presented stimulus in a retro-cue-based working memory experiment. In order to identify the most discriminative stimulus, the single-trial classification accuracies of some Support Vector Machines, trained on the theta, alpha and beta electroencephalography power bands, have been compared; while, in order to identify the most involved brain regions, three machine learning feature reduction techniques have been explored: the first based on a massive univariate analysis, the second based on multivariate filtering and wrapping, and the last one based on Frequency-based Common Spatial Pattern. The results have shown that the univariate approach, more than the others, managed to clearly identify for each participant at least one preferential type of stimulus and a brain region of discriminative electrodes during the maintenance of the stimulus. These promising results can be interpreted as a further step to optimize the Neurofeedback working memory enhancement through a personalised approach.

Anxiety disorders are among the most commonly diagnosed class of mental illness in the United States, and often involve abnormally high levels of stress and social fear. Despite high lifetime prevalence rates, social anxiety disorder (SAD) has remarkably low diagnosis and treatment rates. Furthermore, while individuals with other specific psychiatric disorders tend to exhibit significant neuropsychological deficits, neuropsychological functioning in individuals with SAD remains largely untested. A majority of the few existing studies concerning neuropsychological performance in SAD samples focus on specific functions, and their limited results are highly mixed. The primary objective of this investigation was to provide a more thorough, broad assessment of both auditory and visual working memory as related to psychometrically-defined social anxiety disorder. In addition, this study aimed to help clarify as to whether such deficits are related to the construct of social anxiety, or whether any potential deficits are better explained by generalized state and/or trait (in-the-moment) anxiety. The implications of a deficit in the visual and/or auditory working memory domains are multifaceted. For example, such a deficit may lead to the inability to detect visual cues in social situations. The inability to process these social cues has the potential to exacerbate some SAD- related symptoms, such as fear of humiliation and judgment. Twenty-nine college students completed both phases of this study, including an assessment of state and trait anxiety as well as social phobia and a four-part working memory battery. An analysis of the Phase II data indicates that individual scores on the four measures of both visual and auditory working memory did not relate to trait and/or state anxiety or psychometrically-defined social anxiety.; Thus, it appears that social, generalized trait, and generalized state anxiety do not relate to a neuropsychological deficit in either type of working memory in this sample population. However, we did find a statistical trend suggesting that as social anxiety increased, there was a relative decrease in visual vs. auditory working memory. This statistical trend remained after covarying for state and trait anxiety respectively. Therefore, future research in this area should examine the discrepancy in performance between the auditory and visual working memory domains as it relates to both diagnosed social phobia and psychometrically-defined social anxiety.

In den letzten Jahren wurde es dank der Entwicklung moderner Bildgebungsverfahren möglich, die neuronalen Korrelate kognitiver Arbeitsprozesse teilweise aufzudecken und immer besser zu verstehen. Durch diese Fortschritte ist es heute möglich, diese identifizierten Systeme im Rahmen der Erforschung psychiatrischer Erkrankungen auf Dysregulationen zu untersuchen. Dabei wird seit einigen Jahren der Suche nach Endophänotypen eine tragende Rolle zuteil. Endophänotypen befinden sich dabei intermediär zwischen dem klinischen Phänotyp und dem für die Krankheit kodierenden Genotyp. Ihre Identifizierung soll in Zukunft dazu beitragen, das nach neuesten Erkenntnissen nicht mehr aktuelle psychiatrische Klassifikationssystem zu reformieren und damit eine krankheitsgerechtere Einteilung der einzelnen Diagnosegruppen zu gewährleisten. In diesem Rahmen wurden in der hier vorliegenden Arbeit drei verschiedene neuronale Systeme, die dem Belohnungssystem, dem verbalen sowie visuell-räumlichen Arbeitsgedächtnis und den Aufmerksamkeitsprozessen zugrunde liegen, in Bezug auf ihre Relevanz als potentielle Endophänotypen getestet. 20 erstgradige Angehörige von schizophrenen Patienten unterzogen sich in diesem Zuge einer etwa einstündigen fMRT- Untersuchung, während der sie Aufgaben zur Aktivierung dieser neuronalen Netzwerke lösen sollten. Die dabei gemachten Funde indizieren Dysregulationen verschiedener neuronaler Areale während aller Aufgaben. In Bezug auf vorherige Studien zu Endophänotypen sowohl mit Angehörigen als auch mit Schizophrenen konnten diese Funde in den wissenschaftlichen Hintergrund eingeordnet werden. Dabei konnten einige vielversprechende Beobachtungen festgehalten werden. Es ergaben sich potentielle Endophänotypen in Bereichen neuronaler Hirnstrukturen, die der Verarbeitung von kognitiven Kontrollprozessen zugrunde liegen. Des Weiteren konnte eine Dysregulation vor allem des rechten anterioren Thalamus konstatiert werden. Auch Hyperaktivierungen in Arealen des PFCs und im prämotorischen Kortex konnten ebenfalls durch Funde anderer Studien bestätigt werden. Zusammenfassend stehen die wissenschaftlichen Forschungen zur Endophänotypenfrage wohl noch am Anfang eines langen, jedoch sehr vielversprechenden Weges, der die aktuellen Klassifikationssysteme in Zukunft revolutionieren könnte. Die ersten Schritte sind getan und müssen nun in weiteren, umfangreicheren und möglicherweise auch präziseren Studien fortgeführt werden.