The present thesis was concerned with the possible constraints set by visual and attentional pre-orthographical factors on visual word recognition in dyslexic individuals. In a first study, we investigated the visual word recognition ability of MT, a young boy with surface dyslexia, by means of a paradigm that measures performance as a function of the eye fixation position within the word, known as the "viewing position effect" paradigm. In well-achieving readers, the viewing position effect is mainly determined by factors affecting letter visibility and by lexical constraints on word recognition. We further quantified MT's sensory limitations on letter visibility by computing visual span profiles, i.e. the number of letters recognizable at a glance. Finally, in an ideal-observer's perspective, MT's performance was compared with a parameter-free model combining MT's letter visibility data with a simple lexical matching rule. The results showed that MT did not use the whole visual information available on letter identities to recognise words. These results can be best accounted for by a reduction of the number of letters processed in parallel. Accordingly, there is growing evidence that some dyslexic children suffer from a deficit in simultaneously processing of multiple visually displayed elements. The aim of the remaining studies was to investigate possible cognitive impairments at the source of the multi-element visual processing deficit in dyslexic children. A computational model of the attentional involvement in multi-object recognition [TVA: Bundesen, C. (1990). A theory of visual attention. Psychological Review, 97(4), 523--47] served as framework for this investigation. In a second study, we used TVA to investigate multi-element processing in two young dyslexic participants, AB and PA. By combining psychophysical measurements with computational modelling, we demonstrated that this multi-element processing deficit stems from two distinct cognitive sources: a reduction of the rate of visual information uptake, and a limitation of the visual short-term memory capacity. These deficits were replicated in a third study, in which the multi-element processing was investigated in three dyslexic individuals, FA, LT and YC. The last study further demonstrated that the multi-element processing deficit observed in dyslexia is not simply due to a sluggish activation of items names, instead of visual processing difficulties. Finally, the generalisability of the multi-element processing deficit has been assessed by comparing report performance of letters vs colour patches. Unfortunately, the results were inconclusive. Taken together, the results of these different studies point to a reduced capacity of processing visual information in parallel (at least for letters), that might constrain visual word recognition.

No description available.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Hoje em dia, a quantidade de usuários que utilizam sites de comércio eletrônico para realizar compras está aumentando muito, principalmente devido à facilidade e rapidez. Muitos sites de comércio eletrônico, diferentemente das lojas físicas, disponibilizam aos seus usuários uma grande variedade de produtos e serviços, e os usuários podem ter muita dificuldade em encontrar produtos de sua preferência. Normalmente, a preferência por um produto pode ser influenciada pela aparência visual da imagem do produto. Neste contexto, os Sistemas de Recomendação de produtos que estão associados a Imagens (SRI) tornaram-se indispensáveis para ajudar os usuários a encontrar produtos que podem ser, eventualmente, agradáveis ou úteis para eles. Geralmente, os SRI usam o comportamento passado dos usuários (cliques, compras, críticas, avaliações, etc.) e/ou atributos de produtos para definirem as preferências dos usuários. Um dos principais desafios enfrentados em SRI é a necessidade de o usuário fornecer algumas informações sobre suas preferências sobre os produtos, a fim de obter novas recomendações do sistema. Infelizmente, os usuários nem sempre estão dispostos a fornecer tais informações de forma explícita. Assim, a fim de lidar com esse desafio, os métodos para obtenção de informações de forma implícita do usuário são desejáveis. Neste trabalho, propõe-se investigar em que medida informações sobre atenção visual do usuário podem ajudar a melhorar a predição de avaliação e consequentemente produzir SRI mais precisos. É também objetivo deste trabalho o desenvolvimento de dois novos métodos, um método baseado em Filtragem Colaborativa (FC) que combina avaliações e dados de atenção visual para representar o comportamento passado dos usuários, e outro método baseado no conteúdo dos itens, que combina atributos textuais, características visuais e dados de atenção visual para compor o perfil dos itens. Os métodos propostos foram avaliados em uma base de imagens de pinturas e uma base de imagens de roupas. Os resultados experimentais mostram que os métodos propostos neste trabalho possuem ganhos significativos em predição de avaliação e precisão na recomendação quando comparados ao estado-da-arte. Vale ressaltar que as técnicas propostas são flexíveis, podendo ser utilizadas em outros cenários que exploram a atenção visual dos itens recomendados. / Nowadays, the amount of users using e-commerce sites for shopping is greatly increasing, mainly due to the easiness and rapidity of this way of consumption. Many e-commerce sites, differently from physical stores, can offer their users a wide range of products and services, and the users can find it very difficult to find products of your preference. Typically, your preference for a product can be influenced by the visual appearance of the product image. In this context, Image Recommendation Systems (IRS) have become indispensable to help users to find products that may possibly pleasant or be useful to them. Generally, IRS use past behavior of users (clicks, purchases, reviews, ratings, etc.) and/or attributes of the products to define the preferences of users. One of the main challenges faced by IRS is the need of the user to provide some information about his / her preferences on products in order to get further recommendations from the system. Unfortunately, users are not always willing to provide such information explicitly. So, in order to cope with this challenge, methods for obtaining user’s implicit feedback are desirable. In this work, the author propose an investigation to discover to which extent information concerning user visual attention can help improve the rating prediction hence produce more accurate IRS. This work proposes to develop two new methods, a method based on Collaborative Filtering (CF) which combines ratings and data visual attention to represent the past behavior of users, and another method based on the content of the items, which combines textual attributes, visual features and visual attention data to compose the profile of the items. The proposed methods were evaluated in a painting dataset and a clothing dataset. The experimental results show significant improvements in rating prediction and precision in recommendation when compared to the state-of-the-art. It is worth mentioning that the proposed techniques are flexible and can be applied in other scenarios that exploits the visual attention of the recommended items. / Tese (Doutorado)

Dans plusieurs tâches de la robotique, la vision est considérée comme l’élément essentiel avec lequel la perception de l’environnement ou l’interaction avec d’autres utilisateurs peut se réaliser. Néanmoins, les artefacts potentiellement présents dans les images capturées rendent la tâche de reconnaissance et d’interprétation de l’information visuelle extrêmement compliquée. Il est de ce fait, très important d’utiliser des primitives robustes, stables et ayant un taux de répétabilité élevé afin d’obtenir de bonnes performances. Cette thèse porte sur les problèmes de localisation et de détection de fermeture de boucle d’un robot mobile en utilisant la saillance visuelle. Les résultats en termes de précision et d’efficacité des applications de localisation et de détection de fermeture sont évalués et comparés aux résultats obtenus avec des approches de l’état de l’art sur différentes séquences d’images acquises en milieu extérieur. Le principal inconvénient avec les modèles proposés pour l’extraction de zones de saillance est leur complexité de calcul, ce qui conduit à des temps de traitement important. Afin d’obtenir un traitement en temps réel, nous présentons dans ce mémoire l’implémentation du détecteur de régions saillantes sur la plate forme reconfigurable DreamCam. / In several tasks of robotics, vision is considered to be the essential element by which the perception of the environment or the interaction with other users can be realized. However, the potential artifacts in the captured images make the task of recognition and interpretation of the visual information extremely complicated. It is therefore very important to use robust, stable and high repeatability rate primitives to achieve good performance. This thesis deals with the problems of localization and loop closure detection for a mobile robot using visual saliency. The results in terms of accuracy and efficiency of localization and closure detection applications are evaluated and compared to the results obtained with the approaches provided in literature, both applied on different sequences of images acquired in outdoor environnement. The main drawback with the models proposed for the extraction of salient regions is their computational complexity, which leads to significant processing time. To obtain a real-time processing, we present in this thesis also the implementation of the salient region detector on the reconfigurable platform DreamCam.

La dyslexie est un trouble neurodéveloppemental nuisant au développement normal de la fluidité en lecture. Certains processus de base à la lecture pourraient être atteints chez les dyslexiques et entraîner des répercussions touchant les représentations de haut niveau des mots en découlant : orthographique, phonologique et sémantique. Un de ces processus de base est le déploiement spatio-temporel de l’attention sur des séquences de stimuli multiples alignés à l’horizontale. L’efficacité de ce déploiement pourrait être étroitement liée à l’expertise en lecture chez les normo-lecteurs, et des irrégularités dans celui-ci pourraient être observées chez des dyslexiques. Malheureusement, la caractérisation de ce déploiement en contexte de reconnaissance de mots écrits, son implication dans la vitesse de lecture et (potentiellement) même dans certaines habiletés langagières demeurent largement sous-spécifiées. Le premier article de cette thèse vise à révéler les divergences du déploiement de l’attention dans le temps et dans l’espace pendant la reconnaissance d’un mot familier chez un groupe d’adultes dyslexiques par rapport à un groupe de normo-lecteurs. Les groupes sont appariés en termes d’âge et de fonctionnement intellectuel. Cet objectif est poursuivi avec la technique de sonde attentionnelle. Les résultats révèlent que les dyslexiques dirigent moins de ressources attentionnelles vers la première lettre d’un mot, ce qui est sous-optimal considérant que la première lettre d’un mot est particulièrement informative sur son identité. Le deuxième article de cette thèse vise à déterminer si les habiletés en lecture de texte et de traitement phonologique chez les dyslexiques peuvent bénéficier d’un entraînement attentionnel court. Un protocole utilisant un entraînement visuo-attentionnel (NeuroTracker) et un entraînement placebo chez une vingtaine d’adultes dyslexiques met en évidence des gains systématiques immédiatement après l’entraînement actif. L’ordre des entraînements (actif puis placebo, ou placebo puis actif) était contrebalancé entre deux groupes. Ces gains s’observent en vitesse de lecture, et même au niveau de la conscience phonologique. Le troisième article de cette thèse apporte finalement une contribution additionnelle significative pour l’évaluation de la vitesse de la lecture chez les adultes universitaires franco-québécois. L’utilisation des phrases-tests d’un outil existant (MNRead) a été intégrée à un protocole de présentation visuelle sérielle rapide pour l’évaluation de la vitesse de lecture. En plus de cet ensemble de phrases-test, quatre autres ensembles de phrases-test ont été normés. L’outil développé permet d’obtenir une mesure de la vitesse de lecture fiable chez un même individu à différentes reprises (Exp. 1) et il satisfait différents standards psychométriques (Exps. 1 et 2), en étant notamment sensible à la présence des difficultés en lecture retrouvées chez les dyslexiques (Exp. 2). En somme, il appert que certains processus visuo-attentionnels sous-tendent l’expertise en lecture et que ceux-ci pourraient présenter des irrégularités chez les dyslexiques. La caractérisation d’un déploiement attentionnel sous-optimal en reconnaissance de mots familiers tout comme les bénéfices obtenus en lecture et en traitement phonologique subséquents à un entraînement attentionnels mettent en lumière l’importance de ces processus de base en lecture. / Dyslexia is a neurodevelopmental disorder that affects the normal development of reading fluency. Deficits affecting basic reading processes may affect dyslexics and would thus alter high-level word representations: orthographic, phonological, and semantic. One of these basic processes is the attentional mechanism that is involved in the visual processing of horizontal multi-element strings such as words. The effectiveness of this mechanism could be closely related to reading expertise in normal readers and anomalies thereof could be observed in dyslexics. Unfortunately, it remains unclear how attention is deployed during visual word recognition and how it may impact on reading speed and potentially on certain language skills. The first article of this thesis aims to shed light on divergences in the deployment of attention through time and space during the recognition of familiar words in a group of adults with dyslexia in comparison to normal readers. These groups were matched in terms of age and intellectual functioning. This objective is pursued with the attentional probe technique. Results reveal that less attentional resources are directed to the first letter of a word in dyslexics, which is suboptimal considering that the first letter of a word has a higher diagnostic value than any other letter position. The goal of the second article is to determine if reading fluency and phonological awareness in dyslexics may benefit from a short attentional training. The effects of an active training using the NeuroTracker program and a placebo training in adults with dyslexia shows systematic gains immediately after active training. The order of the training (active then placebo, or placebo then active) was counter-balanced across two groups. These gains are observed on reading speed as well as on phonological awareness. The third article of this thesis finally brings a significant additional contribution to the evaluation of reading speed among Quebec university students. The use of test sentences from an existing tool (MNRead) has been incorporated into a rapid visual serial presentation protocol to assess reading speed. In addition to this set of test sentences, four other sets of test sentences have been standardized. The tool is reliable, as reading speed measurements are similar in the same individual at different times (Exp 1). Moreover, it meets different psychometric standards (Exps 1 and 2) while being particularly sensitive to the presence of the reading difficulties found in dyslexics (Exp.2). In sum, it appears that particular visual-attention processes underlie reading expertise and that these show anomalies in dyslexics. The characterization of a suboptimal attention deployment in visual word recognition as well as the benefits obtained in reading and phonological awareness subsequent to an attentional training highlight the importance of these basic processes in reading.

The visual sense has outstanding importance for humans’ interaction with the environment and visual attention is the key mechanism that bundles our limited cognitive resources in order to enhance the perceptual processing of the most relevant environmental features at a certain point in time. Eye-Tracking technology enables us to accurately observe peoples’ eye movement behavior i.e. overt attention. In the last decade, overt attention on real-world scenes gained increasing popularity in vision research. The higher ecological validity of such scenes in combination with a free-viewing task allows us to investigate human viewing behavior under natural conditions. In this context, the majority of previous studies focused on the impact of basal image properties, such as color and luminance differences, to quantify the extent to which our fixation behavior is guided by these so-called low-level image properties. However, in most experimental studies complex images are observed only one time, whereas we are continually confronted with repeated visual impressions in everyday life. Therefore, I introduce a repeated-presentation-design that allows scrutinizing the impact of low-level image properties and the power of scene types over time. Besides these low-level factors, I also address inter-individual differences in motivation as well as emotional components as so-called high-level factors in overt attention. Previous research on visual attention has widely neglected these factors, especially in the context of real-world images. On the basis of novel study designs and by means of various analysis techniques, I show how several low- and high-level factors influence overt attention on complex scenes, how they interact, and how eye movement parameters are interrelated. In addition to that, I provide a comprehensive review of the previous literature on emotions’ and personality traits’ impacts on visual attention. On the basis of the inconsistent understanding of core concepts in the literature, I describe how behaviorally oriented studies investigate these high-level factors in visual attention, how the interplay between emotion and attention is conceptualized from a neuroscientific perspective, and I derive several conceptual and practical recommendations for future research. Finally, I outline some new ideas and venues for future research in the general discussion of the present work, for example how eye-tracking might overcome some fundamental problems of classical testing in psychological diagnostics, or how the view of embodied cognition can help us to get a better understanding of high- and low-level factors in visual attention.

The video on demand streaming is raising drastically in popularity, bringing new challenges to the video coding field. There is a need for new video coding techniques that improve performance and reduce the bitrates. One of the most promising areas of research is perceptual video coding where attributes of the human visual system are considered to minimize visual redundancy. The visual attention only makes it possible for humans to focus on a smaller region at the time, which is led by different cues, and with deep neural networks it has become possible to create high-accuracy models of this. The purpose of this study is therefore to investigate how adaptive quantization (AQ) based on a deep visual attention model can be used to improve the subjective video quality for low bitrates. A deep visual attention model was integrated into the encoder x265 to control how the bits are distributed on frame level by adaptively setting the quantization parameter. The effect on the subjective video quality was evaluated through A/B testing where the solution was compared to one of the standard methods for AQ in x265. The results show that the ROI-based AQ was perceived to be of better quality in one out of ten cases. The results can partly be explained by certain methodological choices, but also highlights a need for more research on how to make use of visual attention modeling in more complex real-world streaming scenarios to make streaming content more accessible and reduce bitrates. / "Video on demand"-streamingen ökar kraftigt i popularitet vilket skapar nya utmaningar inom video kodning. Det finns ett behov av nya videokodningstekniker som ökar prestanda och reducerar bithastigheten. Ett av de mest lovade forskningsområdena är perceptuell videokodning där man tar hänsyn till synens egenskaper för att minimera visuell redundans. Det visuella fokuset gör att människan bara kan fokusera på ett mindre områden åt gången, lett av olika typer av signaler, och med hjälp av djupa neurala nätverk har det blivit möjligt att skapa välpresterande modeller av det. Syftet med denna studie är därför att undersöka hur adaptiv kvantisering baserat på en djupinlärningsmodell av visuellt fokus kan användas för att förbättra den subjektiva videokvaliteten för låga bithastigheter. En djup modell av visuellt fokus var integrerad i videokodaren x265 för att kontrollera hur bitarna ditribueras på bildnivå genom att adaptivt sätta kvantiseringsparametern. Den subjektiva videokvaliteten utvärderades genom A/B tester där lösningen jämfördes med en standardmetod för adaptiv kvantisering i x265. Resultaten visar att den visuellt fokus-baserade adaptiva kvantiseringen upplevdes ge bättre kvalitet i ett av tio fall. Detta resultat kan delvis förklaras av vissa metodval, men visar också på ett behov för mer forskning på hur modeller för visuellt fokus kan användas i mer komplexa och verkliga streamingscenarion för att kunna göra innehållet mer tillgängligt och reducera bithastigheten.

Within the prefrontal cortex, the frontal eye field (FEF) and the inferior frontal junction (IFJ) are crucial regions that mediate attention, working memory, and cognitive control functions. I comprehensively reviewed the neuroimaging evidence on these regions, suggesting that they are specialized in the control of spatial versus non-spatial visual processing, respectively, and hypothesized that their connectivity fingerprints might underlie these roles. To accurately infer the localization of these regions in standard space, I carried out an activation likelihood estimation (ALE) fMRI meta-analysis using tasks that reliably engage these regions. Prosaccade and antisaccade tasks were included in the FEF sample, whereas oddball/attention, n-back, Stroop and task-switching experiments were included in the IFJ sample (n = 35 and 32, respectively). The ALE technique revealed the strongest convergence of activations at the junctions of the superior precentral sulcus and superior frontal sulcus for the FEF, and the inferior precentral sulcus and inferior frontal sulcus for the IFJ. I employed the resulting ALE peaks to perform a meta-analytic connectivity modeling analysis to uncover their whole-brain fMRI coactivations and decoded these patterns to infer significant associations with behavioral domains. The ALE peaks from a subsample of the previous meta-analysis were used to analyze 3T diffusion MRI data released by the Human Connectome Project from 56 unrelated subjects. Using a surface-based probabilistic tractography approach, I tracked streamlines ipsilaterally from the FEF and IFJ to regions of the dorsal and ventral visual streams on the native white matter surface parcellated using the atlas by Glasser et al. (2016). By contrasting their connectivity likelihood, I found predominant structural connectivity from FEF to regions of the dorsal visual stream (particularly in the left hemisphere) compared to the IFJ, and conversely, predominant structural connectivity from the IFJ to regions of the ventral visual stream compared to the FEF. These results were replicated when accounting for the distance between FEF, IFJ, and the target regions. The connectivity fingerprints of the FEF and IFJ provide converging evidence of their specialization in the control of spatial vs non-spatial processing, which is mediated by long-range white matter association pathways. The results presented in this dissertation overall support the view that the two-visual stream architecture extends to the human prefrontal cortex, as was originally hypothesized in the macaque based on tract tracing and neurophysiological evidence.

A European project is gradually replacing the current train control systems to a mutual control system called as the European Railway Traffic Management System (ERTMS). I Sweden they have implemented the new train control system on a few train-lines in the northern part of Sweden. There has been reported problems from train drivers that have used the new control system, the problems consist of both negative affects on train performance and railroad capacity. This study is part of a larger project conducted by The Swedish National Road and Transport Research Institute, with an aim to investigate how the attention is affected in the new train control system compared to the Automatic Train Control (ATC) system. Data collection through eye-tracking have shown significant results in the distribution of visual glances inside and outside the cabin of the train. Drivers tend to distribute more and longer glances inside the train with the ERTMS. Drivers also tend to miss information presented on the track, such as signs informing when to make a sound before an unattended level crossing. These results suggest that ERTMS could have a negative impact on the drivers situation awareness and also could have a negative affect on the drivers attention that impacts the ability to notice what is happening outside the cabin. / I dagsläget utförs ett projekt i Europa med syfte att ersätta nuvarande tågskyddssystem till ett gemensamt signalsystem kallat ERTMS (European Railway Traffic Management System). Detta nya system har implementerats på ett fåtal tåg-linjer i norra delen av Sverige. Olika problem har rapporterats från tågförare som använt det nya signalsystemet. Dessa problem innefattar negativ påverkan på prestation och järnvägens kapacitet. Denna studie är en del av ett större projekt hos Statens väg- och transportforskningsinstitut med ett syfte att studera hur uppmärksamhet påverkas i det nya tågskyddssystemet ERTMS jämfört med det nuvarande systemet ATC (Automatic Train Control). Data som samlades in via eye-tracking har visat signifikanta resultat i fördelning av visuella blickar inne i och utanför tågets kabin. Förare tenderar att fördela mer och även längre blickar inuti tågets kabin med ERTMS. Dessutom tenderar förare att missa information som presenteras ute på spåret, detta kan exempelvis vara information som påvisar att tuta innan ett obevakat övergångsställe. Dessa resultat föreslår att ERTMS kan ha en negativ påverkan på förares uppmärksamhet vilket kan påverka förarens förmåga att bli varse om vad som händer utanför kabinen, på spåret.

Summaries in Afrikaans and English / Text in Afrikaans / Die waarde van visueel-perseptuele skoling of terapie vir visueel-perseptueel gestremde leerlinge as 'n subgroep van leergestremdheid, is reeds vir dekades 'n omstrede aangeleentheid. Hierdie omstredenheid is ondersoek aan die hand van sewe internasionaal erkende psigometriese toetse. Die interne konsekwentheidskoeffisiente van hierdie toetse het vir die huidige studie van 0,62 tot 0,95 gestrek. 'n Faktorontleding van die toetsinterkorrelasies het 'n gemeenskaplike faktor blootgele. Ses toetse was primer visueel-perseptueel, en Goodenough <1926> se skaal is vir die bepaling van intelligensie gebruik. Bykomend hiertoe, is leerlinge se prestasies in hul eerste taal, wiskunde en skrif gebruik om die effek van terapie te bepaal. Proefpersone is as visueel-perseptueel gestremd gediagnoseer deur 'n opvoedkundige sielkundige en 'n visuele skolingsentrum in Pretoria, waar eksper imentele leerlinge terapie ontvang het. Hierdie diagnoses is deur die Test for Visual Analysis Skills wat beduidend tussen normale en visueelperseptueel gestremdes onderskei, bevestig. Die toets se geldigheid vir Suid-Afrikaanse omstandighede is in 'n voorstudie bepaal. Honderd en ses, ses- tot negejarige proefpersone (82 seuns en 24 dogters>, van normale intelligensie, gesigskerpte en gehoor, is betrek. Drie en vyftig het die eksperimentele groep gevorm wat onderverdeel is in 32 wat terapie voltooi het, en 21 wat nie het nie. Hierdie leerlinge is individueel afgepaar met kontroleleerlinge van dieselfde geslag, ouderdom, huistaal, sosio-ekonomiese status en skoolstanderd. Eksperimentele leerlinge het visuele terapie in n breer groepsverband vir een uur per week ontvang. Terapieperiodes het van 4 tot 15 maande gewissel. Die eksperimentele ontwerp was 'n voortoets-natoets-tweegroepontwerp. t-Toetse vir afhanklike (afgepaarde) groepe is uitgevoer op die verskille tussen voor- en natoetstellings, asook tussen die eksperimentele en kontrolegroepe. Geeneen van die primer visueel-oerseptuele meettegnieke het beduidende resultate opgelewer nie. Dit is aanduidend van die ondoeltreffendheid van visueel-perseptuele terapie om die tekorte waarop dit gemik is, reg te stel. Die waarde van visueel-perseptueie terapie is inteendeel beperk tot 'n oorhoofse verbetering in konseptualisering en intellektuele ryping by die groep wat terapie voltooi het. Skrif was die enigste vak wat by dieselfde groep beduidend verbeter het. Hierdie resultaat is egter twyfelagtig vanwee beoordelingstekorte. / The value of visual perceptual training or therapy, to visually perceptually impaired pupils as a subgroup of the learning disabled, has been a controversy far decades. This controversy was investigated by means of seven internationally recognised psychometric tests. The internal consistency coefficients of these tests for the present study ranged from 0,62 to 0,95. A factor analysis of test intercorrelations revealed a common factor. Six tests were primarily visual perceptual, whilst the Goodenough (1926) scale determined intelligence. Additionally, pupils' performance in their first language, mathematics and writing, was used to assess the therapeutic effect. Subjects were diagnosed as visually perceptually impaired by an educational psychologist and a visual training centre in Pretoria where experimental pupils received therapy. These diagnoses were confirmed by the Test for Visual Analysis Skills, which significantly differentiates between the normal and visually perceptually impaired. This test's validity for South African circumstances was determined in a prestudy. One hundred and six, six to nine year old subjects <82 boys and 24 girls>, of normal intelligence, visual acuity and hearing, were involved. Fifty three formed the experimental group which was subdivided in 32 who completed therapy, and 21 who did not. These pupils were individualiy matched with controls of similar sex, age, home language, socio economic status and school standard. Experimental pupils received visual therapy within a broader group context for one hour per week. Therapy periods fluctuated between 4 and 15 months. The experimental design was a pretest-posttest two group design. t-Tests for dependant <matched) groups were conducted on the differences between pre and oosttest scores, as well as between the experimental and control groups. None of the primarily visual perceptual tests revealed significant results. This signifies the inefficiency of visual perceptual therapy to rectify the deficits at which it is directed. The value of visual perceptual therapy is, on the contrary, restricted to an overall improvement in conceptualization and intellectual maturation within the group which completed therapy. Writing was the only subject which improved significantly within the same group. However, this result is dubious, due to evaluation deficits. / Psychology / D.Litt. et Phil. (Psychology)