Confidence and feedback in visual perceptual learning

The classical view that perceptual learning is highly specific to the stimulus properties used during training is being challenged by accumulating evidence of transfer under specific conditions. Perceptual learning in the adult brain may result from an element of cortical reorganisation at a perceptual level or a reorganisation of decision weights at a higher level. This thesis focuses on individual differences in perception, and the mechanisms of perceptual learning. Since the role of feedback is not usually the primary area of interest for perceptual learning research, this was one of the main focus points of the methodology used. Perception and perceptual learning were assessed for a range of tasks at local and global levels, including depth perception in random dot stereograms, and global motion and form coherence. The results of these experiments established that transfer occurred when the task matched the tuning of the global processing area, even when the untrained task was a locally processed task. The results also provided evidence of robust learning in local and global tasks with or without feedback, as long as easy and difficult trials were interleaved within the same task. Furthermore, in some conditions internal feedback provided better learning at sub-threshold stimulus levels than did explicit external feedback. These results suggest that, for low stimulus intensities, external feedback may reduce observers' confidence in their own perceptual decisions. Confidence in perceptual decisions was a key factor throughout all the studies, and where this was measured it was found to be highly correlated with performance. Confidence in perceptual decision and accuracy was low for a depth perception study using anti-correlated random-dot stereogram (ACRDS). The binocular energy model of neural responses predicts that depth from binocular disparity may be perceived in the reversed-direction when the contrast of dots are anti-correlated. Depth was mostly perceived in the correct direction for ACRDS conditions with some inconsistencies. These differences are likely to reflect the inconsistent depth signals, across scale and across first- and second-order channels, elicited by anticorrelated stimuli. To ensure that the rich variability embedded within the individual differences in heterogeneous data sets were not excluded from analyses, mixed effects models were employed throughout the thesis. This technique considers between-individual variation as a random factor which made it possible to investigate behavioural differences between individuals with migraine and control groups. Specifically we evaluated the spatial extent of excitatory and inhibitory interactions using a classic lateral masking task. Overall, contrast thresholds in the baseline condition for the migraine group were lower than those in the control group. There was no difference in the degree of lateral interaction in the migraine group. The results suggest the that impaired performance in perceptual tasks in individuals with migraine may not be as a results of altered local mechanisms

Irish Passage tombs : Neolithic images, contexts and beliefs

This thesis seeks to take the motifs on Irish Passage tombs beyond their traditional role as passive epiphenomenon and furthers understands them as performing active roles in the Neolithic. Rather than view the images through a textual representational analogy, I utilise visual cultural and neurological studies, set within a worldview perspective to paint a picture of the possible ambiguities of life and belief at some passage tomb locations. I explore the richness of evidence from the archaeological data and literature, to move beyond previous positions, and suggest new ways to deal with a past that develops multiple narratives. Such an account is thick with paradoxes, similarities, differences, tensions, emotions, life, death, pleasures and pain. Visions, context and belief layered together often generate ruptures in daily life that can facilitate new imaginings within the rhythms and sequences of images. Within such a perspective the Irish passage tomb motifs present fresh conditions for possibility and diverse understanding. In combining broader and more fine-grained analysis of particular passage tomb sites located in the north, east and south of Ireland, I demonstrate that social complexities operate at all scales. Magnified via cosmological perspectives, images on passage tombs interact with spectators through two-way intimate engagements. The assemblages that accompany the motifs are not static, instead they display notions of material animacy. Humans do not control all these interactions, for the motifs and objects are dynamic montages. These actions can be enhanced via process, such as the sequential nature of some images or by the application of liquid solutions, especially when conducted at particular times and places. With passage tombs acting as 'stages' and 'islandscapes', I construct interpretations that include both carnivalesque and axis mundi environments, which subvert, disrupt and perpetuate social beliefs. Such performances may have created dialogues and myths about the specialness of these places. These conversations would in turn factor and texture new illusions and simulations of the world, whilst creating fresh opportunities for experience.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Consciousness Science: A Science of What?

While the search for scientific measures, models and explanations of consciousness is currently a growing area of research, this thesis identifies a series of methodological problems with the field that suggest that ‘consciousness’ is not in fact a viable scientific concept. This eliminativist stance is supported by assessing the current theories and methods of consciousness science on their own grounds, and by applying frameworks and criteria for ‘good’ scientific practice from philosophy of science. A central problem consists in the way that qualitative difference and dissociation paradigms are misused in order to identify measures of consciousness. Another problem concerns the wide range of experimental protocols used to operationalise consciousness and the implications this has on the findings of integrative approaches across behavioural and neurophysiological research. Following from this the way that mechanisms of consciousness have been inadequately demarcated, and how this affects whether ‘consciousness’ refers to any scientific kinds, is discussed. A final problem is the significant mismatch that exists between the common intuitions and phenomenological claims about the content of consciousness that motivate much current consciousness science, and the properties of neural processes that underlie sensory and cognitive phenomena.It is argued that the failure of these methods to be appropriately applied to the concept of consciousness, both in particular cases, and in the way that these methods fail to fulfil their crucial heuristic role in the practise of science, suggests that the concept of ‘consciousness’ should be eliminated from scientific discourse. Aside from the purely negative claim found in eliminativist accounts, the strong empirical grounding of this eliminativist claim also allows positive characterisations to be made about the products of the current science of consciousness, to (re-)identify real target phenomena and valid research questions for the mind sciences, and to suggest how the intuitions that ground the confused research program on consciousness result from real features of our cognitive architecture

Reading Ecclesiastes : Old Testament exegesis and hermeneutical theory.

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN009682 / BLDSC - British Library Document Supply CentreGBUnited Kingdo