The ability to locate symbols on a visual display forms an integral part of the effective use of AAC systems. Characteristics of display design and perceptual features of symbols have been shown to influence rate and accuracy of symbol location (Thistle&Wilkinson, 2009; Wilkinson, Carlin,&Jagaroo, 2006). The current study endeavoured to compare the use of two colour-coded organisational strategies (alphabetical order and categorisation) for their effectiveness in symbol location and to investigate if some bottom-up features influenced the performance of the participants in these tasks. 114 learners in Grade 1 to 3 in a mainstream school were randomly divided into two groups. Both of the groups were exposed to two visual search tests in alternating order. The tests involved searching for 36 visual targets amongst 81 coloured Picture Communication Symbols on a computer screen in one of two colour-coded organizational methods, namely alphabetical order or categorisation. The data from the research task was collected through computer logging of all mouse selections. Findings showed that locating symbols on a computer screen with a categorisation strategy was significantly faster and more accurate than with an alphabetical strategy for the Grade 1 to 3 participants. The rate and accuracy of target symbol location in both the strategies decreased significantly as grade increased, as did the differences between rate and accuracy of target location when using the two strategies. It was also found that although the tests in this study placed heavy top-down processing demands on the participants, there was still evidence of bottom-up factors influencing their performance. Implications for display design in AAC clinical practice were discussed. / Thesis (PhD)--University of Pretoria, 2012. / Centre for Augmentative and Alternative Communication / unrestricted

THIS THESIS IS IN THE EXAMINATION PROCESS The ability to locate symbols on a visual display forms an integral part of the effective use of AAC systems. Characteristics of display design and perceptual features of symbols have been shown to influence rate and accuracy of symbol location (Thistle&Wilkinson, 2009; Wilkinson, Carlin,&Jagaroo, 2006). The current study endeavoured to compare the use of two colour-coded organisational strategies (alphabetical order and subcategorisation) for their effectiveness in symbol location and to investigate if some bottom-up features influenced the performance of the participants in these tasks. 114 learners in Grade 1 to 3 in a mainstream school were randomly divided into two groups. Both of the groups were exposed to two visual search tests in alternating order. The tests involved searching for 36 visual targets amongst 81 coloured Picture Communication Symbols on a computer screen in one of two colour-coded organizational methods, namely alphabetical order or subcategorisation. The data from the research task was collected through computer logging of all mouse selections. Findings showed that locating symbols on a computer screen with a subcategorisation strategy was significantly faster and more accurate than with an alphabetical strategy for the Grade 1 to 3 participants. The differences between the rates and accuracy of target symbol location using the two strategies decreased significantly as grade increased. It was also found that although the tests in this study placed heavy top-down processing demands on the participants, there was still evidence of bottom-up factors influencing their performance. Implications for display design in AAC clinical practice were discussed. / Thesis (PhD)--University of Pretoria, 2012. / Centre for Augmentative and Alternative Communication (CAAC) / Unrestricted

En raison de l’hétérogénéité et de l’extravagance de leur contenu, les lapidaires ont souvent été délaissés et restent, encore à ce jour, très peu considérés dans les études sur la littérature médiévale. Le nombre important de manuscrits répertoriés attestent pourtant de leur grande popularité et de la place qu’occupaient les pierres précieuses dans la société et la littérature médiévales. Le lapidaire anonyme tanscrit par le manuscrit Paris, BnF, fonds français, 2007, un lapidaire en prose daté du XVe siècle, n’est à ce jour abordé que dans une seule étude, celle de Barbara Geromel, qui s’est intéressée surtout à un autre témoin (le Turin, Biblioteca Reale, Varia 110) dont le contenu – même s’il est incomplet – correspond en tout point à celui du manuscrit de Paris. Ce lapidaire en prose s’inscrit dans une histoire longue et riche, celle des pierres précieuses depuis l’Antiquité, mais s’en démarque également par son organisation complexe de la matière, puisqu’il adopte de manière partielle et imparfaite le paradigme alphabétique, jusqu’alors très peu employé dans les encyclopédies dû aux tensions qu’il incarnait vis-à-vis l’ordre théologique. Témoin matériel d’une sphère plus considérable encore – celle de l’encyclopédisme médiéval –, ce lapidaire participe à la compilation du savoir de jadis et invite à une étude plus approfondie, à la fois de la matière qu’il recèle, de ses sources, issues d’une quantité importante de traditions manuscrites, et de son classement alphabétique. / Regarding the heterogeneity and extravagant nature of their content, the lapidaries have too often been put aside from studies concerning medieval literature, and, still to this day, only a few of them have been studied by scholars. However, the very high number of known manuscripts of such texts does tell us a lot about the popularity and the role played by precious gems within medieval society and litterature. The prose lapidary copied in ms Paris, BnF, fonds français, 2007, a prosaic lapidary dated from the XVth century, has yet only been mentioned once, in a study by Barbara Geromel, who was mostly interested by another manuscript – albeit incomplete – of the same text : ms Turin, Biblioteca Reale, Varia 110. The content remaining in this manuscript corresponds precisely to the one found within the Paris manuscript. This manuscript written in prose represents one single step in a long and rich history (the tradition of describing precious stones dating back to the Antiquity). Nervertheless, it also differs from this tradition by its complex inner organisation of the subject, since it puts to use to this effect an imperfect and incomplete alphabetical paradigm as a mean of classification, an unpopular paradigm at the time, as it embodied elements difficult to correlate with the theological order. This lapidary, a material witness of an even larger intelectual context – the world of mediaeval encyclopedism –, participates to the compilation of knowledge from older times, and calls for deeper studies of its general content, sources (themselves coming from varied manuscript traditions) and usage of an alphabetical classification.