Bibliography: leaves 351-362 / xxiii, 362 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Psychology, 1983

How should we account for our ability to entertain simple, vision-based demonstrative thoughts about particular objects (that is, our ability to entertain thoughts about particular objects simply on the basis of seeing them)? In this thesis I propose an account of this ability that accords with the common-sense view that seeing an object puts one in a position to single it out by visually attending to it, and that this provides one with the ability to entertain demonstrative thoughts about it. An account of this type requires that we account for what it is to see a particular object and to visually attend to it without appealing to particular demonstrative abilities. However, it has been argued that a notion of seeing an object, and similarly a notion of attending to an object, which is accounted for in this way is unsuitable for accounting for demonstrative abilities. I argue that there is no real problem: what we need is a notion of experiential content which is concept-dependent only in a general manner. That is, the account of the relevant notion of experiential content requires appeal to the subject's conceptual abilities, but the account is not given in terms of specific conceptual abilities (especially, not specific demonstrative abilities). I then characterize a notion of attention to a seen object which can be accounted for without appeal to particular demonstrative abilities, and explain how attending to an object in the relevant sense provides the subject with the ability to think about the object demonstratively. It is widely agreed that spatial location plays a central role in an account of demonstratives. I explain this role in terms of the role played by location in visual attention to the object and the subject's grasp of the fact that he attends to the object.

Bibliography : leaves 246-257 / v, 257 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Psychology, 1990

Many tasks in the real world require simultaneous processing of mental information alongside physical activity. Most of researchers have studied the impact of physical activities on simple cognitive tasks, but have neglected other important influences (such as different attentional resource pools, as well as gender). Therefore, this thesis proposes a new model that investigates the combined impact of physical and mental workload on different attentional resources (visual and auditory, verbal and spatial). This thesis presents three experimental studies that examined the effects of physical and mental workload interactions, as well as gender, on visual tasks performance and auditory tasks. This thesis uses different methods to evaluate the impacts of workload interactions on task performance: performance measure, physiological parameters and brain activity (Near-Infrared Spectroscopy (NIRS) method) and subjective assessment tools. Finally, this thesis translates the experimental studies setting into a field study to validate the model. Based on the experimental results, this research creates a new theoretical model that illustrates in general that physical activity is beneficial for performance on cognitive tasks (visual and auditory), particularly at low levels of workload interactions, while other workload interactions lead to worse performance on cognitive tasks. However, when physical activity was introduced, performance at the medium level of mental workload was equivalent to that in the low mental workload condition; furthermore, at the low mental workload, there were no differences in performance between low and medium physical workloads. The general pattern of results suggests that physical workload leads to better performance in these medium-demand conditions up to the higher level in the low-demand condition. A mechanism for this effect is proposed based on physiological arousal and brain oxygenation. This thesis further suggests that the NIRS is a valuable technique to reflect the influence of physical and mental workload interactions on brain activity. Finally, this thesis demonstrates the translation of experimental findings into a field setting to verify the new model as well as to make recommendations for job design.

Reward expectation and spatial attention both exert powerful control over behaviour and modulate neural activity. The experiments in this thesis aimed to chart the dynamics of reward expectation effects across the time course of information processing and examine the relationship between reward and attention. Experiments 3.1 and 3.2 parametrically manipulated reward magnitude in the presence or absence of attention and demonstrated reward could influence reaction time (RT) under conditions of time pressure. Experiments 4.1 and 4.2 independently varied reward and spatial probabilities and illustrated independent and interactive effects of reward and attention at late stages of cognitive processing (the P300 potential), as well as modulation of detection sensitivity (d') by reward under conditions of uncertainty when reward was able to work through feature-based attention. The experiment of Chapter 5 cued reward and attention trial by trial and showed under these conditions, not only could reward influence late stages of information processing, but expectation of reward reduced peak latency of the visual N1 potential. Reward and attention also modulated motor preparation with both independent and interactive effects. The experiment of Chapter 6 examined the dynamics of reward association with task-relevant targets and irrelevant distracters during visual search and demonstrated that task-irrelevant but motivationally-salient distracter items could capture attentional resources away from the target, guided by endogenous reward association alone. The experiments of this thesis demonstrated the ability of reward expectation to modulate both behaviour and multiple stages of information processing, with effects predominantly independent from those of attention. Reward could influence processing from early visual analysis and target detection stages. Interaction between the two systems occurred at late processing stages, whereby reward and attentional information may have been integrated to provide a cohesive representation of the stimulus given the current environmental conditions.

Un aspect fondamental du contrôle attentionnel réside dans la capacité du sujet à anticiper l’apparition d’un stimulus afin de rendre son traitement plus rapide et plus efficace. L'attention préparatoire (AP) est la capacité de moduler (rehausser) l’intensité de l’attention dirigée vers un stimulus sélectionné avant son apparition, en empêchant que le sujet soit distrait par une information non pertinente. Certaines études soutiennent que l’AP est latéralisée dans l’hémisphère droit (HD) alors que d’autres suggèrent que les deux hémisphères, l’hémisphère gauche (HG) et l’HD, sont impliqués dans la modulation de l’AP. L’objectif de cette thèse est d’analyser le rôle joué par chaque hémisphère cérébral dans la modulation de l’AP dirigée vers une localisation de l’espace. Nous avons développé une version latéralisée du test APT (pour Attentional Preparatory Test, proposé par LaBerge, Auclair & Siéroff, 2000), le LAPT (Lateralized Attentional Preparatory Test). L’APT permet de mesurer la capacité des sujets à moduler leur AP vers la localisation d’une cible lorsque la probabilité d'un distracteur varie selon plusieurs blocs d’essais. Dans l’APT, le temps de réponse augmentait lorsque la probabilité d’apparition d’un distracteur dans la phase préparatoire antérieure à la présentation de la cible augmentait, ce qui montre que l’AP est modulée par des évènements antérieurs au traitement de la cible. Nous avons créé le LAPT en utilisant la méthode de présentation en champ visuel divisé dans laquelle les stimuli peuvent apparaître dans le champ visuel gauche (CVG) ou dans le champ visuel droit (CVD). Les différences de performances entre champs visuels nous donnent des indications sur les stratégies de traitement des deux hémisphères (CVD/HG vs CVG/HD). Dans une série d’études, nous avons montré que la modulation de l’AP en fonction de la probabilité attendue d’un événement diffère dans chaque champ visuel/hémisphère en fonction de la configuration de la tâche. Dans le CVD/HG, l’AP est modulée par la probabilité des événements distracteurs, surtout quand cette probabilité est explicite. De plus, l’HG semble tenir un rôle crucial dans la modulation de l’AP quand la cible et le distracteur sont difficiles à discriminer. Dans le CVG/HD, l’AP est modulée par la probabilité temporelle des événements et dépendrait du délai le plus probable dans lequel la cible est attendue, mais seulement lorsque la discrimination entre la cible et le distracteur est plus facile. Enfin, nos résultats suggèrent que les différences entre le CVD/LH et le CVG/RH lors de cette modulation attentionnelle se mettent en place à un niveau perceptif du traitement de l’information car ils sont indépendants de la main utilisée pour répondre et donc des processus requis au niveau de la programmation motrice. L’ensemble de ces résultats suggère que chaque hémisphère utilise une stratégie différente pour moduler l’AP lorsqu’elle est dirigée vers une localisation de l’espace. / A crucial aspect of attentional control is the capacity of anticipating a stimulus appearance in order to improve the speed and effectiveness of its subsequent processing. Preparatory attention (PA) is the ability to modulate (enhance) the intensity of attention directed to a selected stimulus prior to its occurrence, preventing subjects from being distracted by interfering stimuli. Some studies propose that PA is lateralized to the right hemisphere (RH) while others suggest that both the left hemisphere (LH) and the RH participate in the modulation of PA. The aim of the present thesis was to examine the role of each brain hemisphere in the modulation of PA directed to a spatial location. We developed a lateralized version of the Attentional Preparatory Test, (APT, proposed par LaBerge, Auclair & Siéroff, 2000), named the Lateralized APT or LAPT. The APT measures the ability of subjects to modulate PA directed to a target location when the probability of a distractor occurrence varies across several blocks of trials. In the APT, the response times increased as the probability of a distractor appearing in the preparatory phase preceding the target presentation increased, showing that PA is modulated by the events occurring prior to the target appearance. We developed the LAPT using the divided visual field paradigm in which stimuli can occur in the left (LVF) or the right (RVF) visual fields. The visual field differences in subjects’ performance are assumed to reflect differences in the processing strategies of both hemispheres (RVF/LH vs LVF/RH). In a series of studies we showed that the modulation of PA by the expected probability of events was different in each visual field/hemisphere, depending on task configuration. In the RVF/LH, PA is modulated by the expected probability of distractor events, especially when this probability is explicit. In addition, the LH seems to play a crucial role in modulating PA when the target and the distractor are hard to discriminate. In the LVF/RH, PA is modulated by the temporal probability of events and may depend on the most probable delay in which the target is expected, but only when the discrimination between the target and the distractor is easy. Most importantly, our findings suggest that the differences between RVF/LH and LVF/RH in the modulation of PA take place at the perceptual level of processing because they are independent of the hand use in executing the response, thus also independent of the processes taking place at the motor programming level. Taken together our results, they suggest that each hemisphere uses a different strategy to modulate PA when directed to a spatial location.