The purpose of this thesis was to explore whether there is a direct route to action from vision, in which the selection of action is constrained by perceptual information from objects as well as by more abstract semantic knowledge. A connectionist model, NAM (Naming and Action Model) was developed, incorporating a direct perceptual route to action along with an indirect semantic route. This was used to simulate data from normal observers and neuropsychological patients. In addition to this, new empirical data were collected to provide a better understanding of the types of visual information used in action selection. One set of new experiments provided evidence that two variables, object viewpoint and semantic priming, differentially affect action and semantic decisions to objects. A further set of experiments showed that action verification tasks (e. g., is this drinking? ) could be facilitated by congruent information about handgrip - provided either by a static or a moving hand. This indicates that a direct route to action is sensitive to linked information about handgrip and movement. Finally, the direct route to action was examined through a case study of an optic aphasic patient. This patient showed spared naming of verbs relative to objects, but the opposite pattern of sparing occurred in reading. This double dissociation, within a patient, suggests that verb retrieval for objects can operate non-semantically. These computational, psychological and neuropsychological data provide evidence for a direct route to action.

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Gibson's (1979) ecological approach to vision and perception suggested that objects hold motoric information that is automatically perceived upon first sight. This is the theory of affordances. Subsequent research has extensively suggested that the simple viewing of an object can automatically elicit motor response codes for relevant actions. In the present PhD thesis this affordance effect hypothesis was examined under experimental conditions that allowed the properties of this effect to be identified, particularly how it is modulated under different types of vision and attention. The methodological approaches applied included measurements of response times to simple motor tasks, as well as measurements of corticospinal excitability by applying transcranial magnetic stimulation (TMS) techniques. Participants viewed real objects (or depictions of these) associated with specific limb actions (i.e. pinching and grasping), thus allowing associations to be drawn between the physical properties of the stimuli and the recorded reaction times or TMS-induced reactions. First and foremost, behavioural and neurophysiological evidence was provided that visual objects can automatically activate motor programmes for congruent actions, even in cases where there is no need to implement these actions. Furthermore, the temporal evolution of the affordance effect was investigated under various experimental conditions. It was found that object affordances are generated soon after first viewing an object (- 300 ms), but dissipate quite rapidly after that (- 600 ms). Finally, the present studies and findings provided strong evidence that vision and attention serve a pivotal role in the generation of the affordance effect, and that variations in how an object is perceived can greatly affect the way affordances are generated. Overall, the present PhD provided experimental evidence on a highly topical field within Psychology and Neuroscience that concerns the relationship between visual perception and motor planning.

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This thesis describes experimental work on the brain mechanisms underlying human visual selective attention, with a focus on top-down activity changes in visual cortex. Using a combination of methods, the experiments addressed related questions concerning the functional significance and putative origins of such activity modulations due to selective attention. More specifically, the experiment described in Chapter 2 shows with TMS-elicited phosphenes that anticipatory selective attention can change excitability of visual cortex in a spatially-specific manner, even when thalamic gating of afferent input is ruled out. The behavioural and fMRI experiments described in Chapter 3 indicate that top-down influences of selective attention are not limited to enhancements of visual target processing, but may also involve anticipatory processes that minimize the impact of visual distractor stimuli. Chapters 4-6 then address questions about potential origins of such top-down activity modulations in visual cortex, using concurrent TMS-fMRI and psychophysics. These experiments show that TMS applied to the right human frontal eye field can causally influence visual cortex activity in a spatially-specific manner (Chapter 4), which has direct functional consequences for visual perception (Chapter 5), and is reliably different from that caused by TMS to the right intra-parietal sulcus (Chapter 6). The data presented in this thesis indicate that visual selective attention may involve top-down signals that bias visual processing towards behaviourally relevant stimuli, at the expense of distracting information present in the scene. Moreover, the experiments provide causal evidence in the human brain that distinct top-down signals can originate in anatomical feedback loops from frontal or parietal areas, and that such regions may have different functional influences on visual processing. These findings provide neural confirmation for some theoretical proposals in the literature on visual selective attention, and they introduce and corroborate new methods that might be of considerable utility for addressing such mechanisms directly.

This investigation deals with the issue of visual perception of the designed object, which is relevant in the context of product differentiation particularly in the case where incremental style changes are made to the external shape design of the product. Such cases present a problem regarding the effectiveness of product differentiation, which this research claims is a matter of visual perception. The problem is that in order for product differentiation to be effective, the design changes must be perceptible. Perceptible differentiation is explained as a function of the physical change, i.e. the Oreal¹ difference, and also of the relevance for the observer of that change, i.e. Operceived¹ difference. This study therefore focuses on the comparison between these two aspects of the designed object: the physical design and the perceived design. Literature from both material culture and the so-called indirect account of perception suggest that visual perception is an interpretation of the artefacts that we see. This visual perception is a function of the physical aspect of that object and of the individual cultural background of the observer. However, it was found that between these two accounts there are theoretical incompatibilities which this study claims could be resolved through scholarly investigation of visual perception of the designed object. The thesis takes these two accounts into consideration and proposes a more comprehensive model of visual perception of the designed object that details and extends the material culture understanding of what constitutes the perceptual experience with the designed object and the role of form in that experience. Theory building was conducted across the disciplines of psychology of perception and design. A revised model was proposed for the area of designed object studies, which was informed by Gregory¹s theoretical framework and incorporated empirical explorations into the model development process. The study therefore contributes knowledge to the research area of design, more specifically to cross-disciplinary methods for theory building on visual perception of the designed object.