Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

I expect, therefore I see: individual differences in visual awareness

Predictive processing theories posit that awareness of the visual world emerges as the brain engages in predictive inference about the causes of its sensory input. At each level of the processing hierarchy top-down predictions are corrected by bottom-up sensory prediction error to form behaviourally optimal inferences about the state of the visual world. Research suggests there may be individual differences in predictive processing mechanisms such that some individuals are more reliant on prior knowledge, whereas others assign more weight to sensory evidence. Predictive processing biases are thought to manifest in a range of typical and atypical perceptual experiences including proneness to perceptual illusions, sensory sensitivity in autism, and hallucinations in psychosis. The overarching aim of this thesis was to investigate whether in the general population predictive processing biases predict individual differences in visual awareness. Change blindness was selected as the central paradigm of investigation, as it can be conceptualised as a failure to incorporate a novel change into the current prediction about the state of the visual world. The empirical work in Chapter 2 aimed to characterise individual differences in visual change detection using naturalistic scenes and to identify the perceptual and cognitive measures that predict noticing ability. There were reliable individual differences in change detection that generalised to ecologically valid displays. The ability to notice visual changes was predicted by the strength and stability of perceptual predictions, as measured by the accuracy of visual short-term memory and attentional control in the face of distractors. In Chapter 3 I used voxel-based-morphometry to investigate whether inter-individual variability in brain structure predicts individual differences in visual awareness. The latter was assessed by the change blindness task as well as its strongest predictor measures (visual short-term memory, attentional capture, and perceptual rivalry). Regions of interest (ROIs) were selected in the parietal and visual cortices based on previous evidence that these areas are causally involved in the awareness of visual stimuli. This study aimed to discover whether the average grey matter density in the ROIs predict susceptibility to CB. The ROI-based analyses revealed the average grey matter density in left posterior parietal cortex predicted visual short-term memory accuracy but none of the other hypothesised relationships were significant. Chapter 4 aimed to measure individual differences in the reliance on prior knowledge by employing the Mooney face detection task. In this task participants disambiguated faces in two-tone degraded images before and after the presentation of the original versions of the images. Better change detection was predicted by Mooney face detection without any prior knowledge of the images, a measure of ‘perceptual closure’ or an ability to generate a gestalt of a scene. The attention to detail subscale of the autism spectrum also predicted superior change detection. Reliance on prior knowledge in visual perception (assessed by improvement in Mooney face detection after seeing original images) did not consistently predict atypical perceptual experiences associated with the autism spectrum or schizotypy. Chapter 5 was an investigation into, firstly, whether there is a general predictive processing bias, which manifests across different methods of inducing prior knowledge, or whether such a bias is paradigm-specific and, secondly, whether reliance on priors predicts perceptual experiences and traits. All prior manipulations in this study lead to an increased tendency to see the expected stimulus in a binocular rivalry display, except adaptation, which lead to a suppression of visual awareness. Attentional control, perceptual priming, expectancy, and imagery loaded onto a common factor, suggesting that the strength of selective attention is closely linked with the facilitatory effect of expectation. The strength of adaptation predicted superior change detection and perceptual priming predicted the propensity to experience perceptual illusions. Taken together, these findings suggest that there are reliable individual differences in visual change detection, and these are predicted by the strength of visual short-term memory representations, attentional control, perceptual closure ability, as well as the strength of low-level adaptation. Possessing expectations facilitates the entry of the corresponding percept into awareness, irrespective of the method of prior induction. The facilitatory effect that priors exert on visual awareness across different methods is closely linked with the ability to exert attentional control. This suggests that the effects of expectations on awareness may be attentional. However, predictive processing biases were method-specific in that a facilitatory effect using one prior induction method will not necessarily predict the magnitude of the effect using a different method. Some prior effects (e.g., perceptual priming, imagery, and adaptation) yielded correlations with perceptual experiences and traits in the general population. As the research in this thesis is correlational, future studies will need to delineate the effects of expectation, attention, and adaptation on visual awareness and explore the neural representations of these mechanisms

Neural correlates of navigation in large-scale space

Navigation and self-localisation are fundamental to spatial cognition. The cognitive map supporting these abilities is implemented in the hippocampal formation. Place cells in the hippocampus fire when the animal is at a specific location – a place field. They are thought to be involved in navigation and self-localisation but usually studied in constrained environments, limiting observable states. In this thesis, I present two experiments studying place cells in large open field environments, a novel auditory cue-triggered navigational task, and a technical solution for conducting large scale automated experiments. Place cells are frequently reactivated during immobility, rapidly replaying trajectories through environments. These replay events are thought to be involved in navigational planning. Using a novel automated cue-triggered navigational task in a large open field environment, I show that replay is not associated with navigation to the goal. Instead, it occurs reliably at the end of successful trials, when an associated reward is received, but not during consumption of scattered pellets. The trajectories in these events are predictive of the animal’s movement after, but not before, the reward. The number of place fields per cell, their size and other properties have not been fully characterised. Using multiple large open field environments of different size, I show that place field size, shape and density changes systematically with distance from walls. However, through a homeostatic mechanism, the mean firing rate and proportion of co-active units in the population remains constant throughout environments, as does the accuracy of their spatial representation. Multiple place field properties are conserved by cells across environments, including the number of fields, which is quantified relative to environment size using a gamma-Poisson model. Place cell population models suggest two sub-populations, with uniform and boundary dependent field distributions. These results provide a comprehensive account of place cell population statistics in different size environments

MYTHOGEOGRAPHIC PERFORMANCE AND PERFORMATIVE INTERVENTIONS IN SPACES OF HERITAGE-TOURISM

Abstract MYTHOGEOGRAPHIC PERFORMANCE AND PERFORMATIVE INTERVENTIONS IN SPACES OF HERITAGE-TOURISM by PHIL SMITH This thesis offers new models for participatory and performative interventions in sites of heritage tourism through a theorized practical engagement. Drawing on both Tourism Studies and Performance Studies, the primary aim of these interventions is to reveal and provoke ways of seeing and using these sites as places of multiple meanings rather than as ones constricted and bounded by normative heritage narratives in their production and management. The experimental phase of the project discussed in the thesis includes three contrasting case studies: GeoQuest, Sardine Street, and Water Walk. These are each analysed and evaluated through my development of a ‘mythogeographic’ framework that includes the performative techniques of layering, rhizomatic interweaving, the making of 'anywheres' and the self-mythologising of the activist. The thesis charts a trajectory through praxis, from developing models for ambulatory, signage-based and ‘mis-guided’ interventions to be undertaken by performance ‘specialists’, towards a dispersal of their tactics for use by heritage tourists in general. It thus describes a related change in the balance of the research methodology from ethnographic participant observation towards practice-as-research (PaR), the latter of which both generated and enacted knowledge and understanding. This PaR took the form of various visits and forays to and across heritage sites and landscape, and also the production of a ‘toolkit’ of handbook, pocketbook, website and online short films for the dispersal of tactics and a strategy that is eventually called ‘counter-tourism’. The thesis thus includes the publications A Sardine Street box of tricks, Counter-tourism: the handbook, Counter-tourism: a pocketbook and the DVD, Tactics for counter-tourism, as well as their fully theorized critical contextualisation. These represent a PaR enquiry that attempts to creatively express my research findings from productions made in the field through a popular form of writing and presentation that is capable of inspiring general, ‘non-specialist’ tourists to make their own performance interventions in heritage sites

Why Hollywood Isn\u27t As Liberal As We Think and Why It Matters

Hollywood has long had a reputation as a liberal institution. Especially in 2019, it is viewed as a highly polarized sector of society sometimes hostile to those on the right side of the aisle. But just because the majority of those who work in Hollywood are liberal, that doesn’t necessarily mean our entertainment follows suit. I argue in my thesis that entertainment in Hollywood is far less partisan than people think it is and moreover, that our entertainment represents plenty of conservative themes and ideas. In doing so, I look at a combination of markets and artistic demands that restrain the politics of those in the entertainment industry and even create space for more conservative productions. Although normally art and markets are thought to be in tension with one another, in this case, they conspire to make our entertainment less one-sided politically. From the role that China plays in Hollywood productions to examining the politics of The Matrix and other pop culture staples, I work to deconstruct the notion that Hollywood and its entertainment are solely a liberal endeavor. Less polarization in entertainment brings forth a variety of important implications, one such being that Hollywood will continue to act as an institution that provides intellectual diversity and entertainment for all

Disrupting the Symbolic Hamlet: A Semiotic Reading

Even though the eruption of Shakespeare’s Hamlet in everyday performative situations, Verities, and the Variable theatrical performative world is common, understood, and accepted over the centuries, the reasons for its return are not fully explored. Deciphering the mechanisms through which it has survived provide a good model for sprouting the contemporary theater of Pakistan. An overview or ‘thinking’ of its semiotic renditions into variegated forms, without analysis based on discrimination, helps in focusing upon some of the essentials that enable the performance text to survive through times. My work involves one such analysis. The objective of this study was to examine two questions: first, why does Hamlet constantly return in the contemporary performance? Second, is there a similar text, character or situation, in Pakistan through which we can structure the performance art of the country? To examine these questions, I explored the literary and performance texts of Hamlet as well as the literary theory, especially Affect Theory and Performance Philosophy. This study displayed a connection between history, culture, affect, and audience. In fact, I could link the Traditional Punjabi Performers of ‘Vaar’ or folk ballads with the performers affected by the strong history and culture based affective field of Hamlet. However, I found Vaari performers relied upon their voice and history based oral narrative and not on the text. This recognition suggests that Pakistan can build upon the historically popular oral narratives to frame its theater. I found that writers steeped in history and cultures of the country have already made such attempts. In future, theater of Pakistan may focus on developing, disrupting and re-performing these narratives. This dissertation highlighted the re-birth of the ‘Vaari’ as the means of reviving performance art in Pakistan.Obwohl der Ausbruch von Shakespeares Hamlet in alltäglichen performativen Situationen, Verities und der variablen theatralisch-performativen Welt im Laufe der Jahrhunderte weit verbreitet ist, verstanden und akzeptiert wird, sind die Gründe für seine Rückkehr nicht vollständig erforscht. Die Entschlüsselung der Mechanismen, durch die es überlebt hat, bieten ein gutes Modell für die Entfaltung des zeitgenössischen pakistanischen Theaters. Eine Übersicht oder ein „Denken“ der semiotischen Darstellungen in verschiedenen Formen, ohne diskriminierende Analyse, hilft dabei sich auf einige der wesentlichen Aspekte zu konzentrieren, die dem Performance-Text das Überleben in den Zeiten ermöglichen. Meine Arbeit beinhaltet eine solche Analyse. Ziel dieser Studie war es, zwei Fragen zu untersuchen: Erstens, warum kehrt Hamlet ständig in die zeitgenössische Performance zurück? Und zweitens, gibt es in Pakistan einen ähnlichen Text, Charakter oder eine ähnliche Situation, durch die wir die Performance-Kunst des Landes strukturieren können? Um diese Fragen zu untersuchen, habe ich die literarischen und Performance-Texte von Hamlet sowie die literarische Theorie, insbesondere die Affekttheorie und die Performance-Philosophie, untersucht. Diese Studie zeigte einen Zusammenhang zwischen Geschichte, Kultur, Einfluss und Publikum. In der Tat könnte ich die traditionellen Punjabi-Darsteller von 'Vaar' mit den Darstellern aus Hamlet in verbindung bringen, die von der starken Geschichte und Kultur des affektiven Feldes von Hamlet betroffen sind. Ich fand jedoch, dass Vaari-Darsteller sich auf ihre Stimme und Geschichte stützten, basierend auf mündlichen Erzählungs und nicht auf den Text. Diese Erkenntis legt nahe, dass Pakistan auf den historisch populären mündlichen Erzählungen aufbauen kann, um sein Theater zu gestalten. Ich fand heraus, dass Schriftsteller, die mit der Geschichte und Kultur des Landes vertraut sind, bereits solche Versuche unternommen haben. In Zukunft kann sich das Theater in Pakistan darauf konzentrieren, diese Erzählungen weiter zu entwickeln, zu variieren und wiederzugeben. In dieser Dissertation wurde die Wiedergeburt des "Vaari" als Mittel zur Aktivierung der Performance-Kunst in Pakistan thematisiert

Eye quietness and quiet eye in expert and novice golf performance: an electrooculographic analysis

Quiet eye (QE) is the final ocular fixation on the target of an action (e.g., the ball in golf putting). Camerabased eye-tracking studies have consistently found longer QE durations in experts than novices; however, mechanisms underlying QE are not known. To offer a new perspective we examined the feasibility of measuring the QE using electrooculography (EOG) and developed an index to assess ocular activity across time: eye quietness (EQ). Ten expert and ten novice golfers putted 60 balls to a 2.4 m distant hole. Horizontal EOG (2ms resolution) was recorded from two electrodes placed on the outer sides of the eyes. QE duration was measured using a EOG voltage threshold and comprised the sum of the pre-movement and post-movement initiation components. EQ was computed as the standard deviation of the EOG in 0.5 s bins from –4 to +2 s, relative to backswing initiation: lower values indicate less movement of the eyes, hence greater quietness. Finally, we measured club-ball address and swing durations. T-tests showed that total QE did not differ between groups (p = .31); however, experts had marginally shorter pre-movement QE (p = .08) and longer post-movement QE (p < .001) than novices. A group × time ANOVA revealed that experts had less EQ before backswing initiation and greater EQ after backswing initiation (p = .002). QE durations were inversely correlated with EQ from –1.5 to 1 s (rs = –.48 - –.90, ps = .03 - .001). Experts had longer swing durations than novices (p = .01) and, importantly, swing durations correlated positively with post-movement QE (r = .52, p = .02) and negatively with EQ from 0.5 to 1s (r = –.63, p = .003). This study demonstrates the feasibility of measuring ocular activity using EOG and validates EQ as an index of ocular activity. Its findings challenge the dominant perspective on QE and provide new evidence that expert-novice differences in ocular activity may reflect differences in the kinematics of how experts and novices execute skills

Saccade Planning and Execution by the Lateral and Medial Cerebellum

In dit proefschrift wordt beschreven hoe het cerebellum saccadische oogbewegingen plant en uitvoert. De resultaten van metingen aan the neuronen in het cerebellum van rhesus makaken geven inzicht in welke processen ten grondslag liggen aan dit type oogbeweging