Perception and reconstruction of two-dimensional, simulated ego-motion trajectories from optic flow.

A veridical percept of ego-motion is normally derived from a combination of visual, vestibular, and proprioceptive signals. In a previous study, blindfolded subjects could accurately perceive passively travelled straight or curved trajectories provided that the orientation of the head remained constant along the trajectory. When they were turned (whole-body, head-fixed) relative to the trajectory, errors occurred. We ask here whether vision allows for better path perception in similar tasks, to correct or complement vestibular perception. Seated, stationary subjects wore a head mounted display showing optic flow stimuli which simulated linear or curvilinear 2D trajectories over a horizontal ground plane. The observer's orientation was either fixed in space, fixed relative to the path, or changed relative to both. After presentation, subjects reproduced the perceived movement with a model vehicle, of which position and orientation were recorded. They tended to correctly perceive ego-rotation (yaw), but they perceived orientation as fixed relative to trajectory or (unlike in the vestibular study) to space. This caused trajectory misperception when body rotation was wrongly attributed to a rotation of the path. Visual perception was very similar to vestibular perception

Set theory ontology as an approach to gaming’s composite form

This paper will explore the possibilities that mathematical set theory has to offer the scholarly study of videogames. Videogames are highly heterogeneous objects of study, comprising what Linderoth (2015) has called a ‘composite form’: complex arrangements of material, symbolic and computational capacities. This composite is becoming ever-more heterogeneous, ‘recruiting’ increasingly volatile bodies and relations as computing resources are newly distributed throughout both built and natural environments to create locative, alternate and virtual realities that have been used by designers in various ways (Pokemon Go being only one example)

“Asexy and we know it”: The Emergence of Asexual Activism as a Sexual and Gender Social Movement

This thesis considers the emerging character of asexual activism in Western societies. It asks what the key factors are impacting on triggering, mobilisation, organisation and performance that motivate asexual-identified individuals into collective activism. It considers the significance of wider LGBT+ and Q activism exemplified by Pride as performed spectacle, as a factor influencing the character of contemporary asexual activism. This is considered both in terms of how the staging, setting and scripting of Pride speaks to asexual activists in the West, and, how they speak back to Pride as actor-activists, audience and bystanders to its political theatre. Methodologically, this thesis is based on 15 months of ethnographic research: online semi-structured interviews with asexual activists in both Europe and North America; auto-ethnographic participant-observation of Pride events in Europe and North America, and, specific case studies of WorldPride 2014 and Berlin Pride 2015. Theoretically, it draws cross-disciplinarily on: insights from Social Movement Theory, particularly recent work which emphasises the significance of emotive, cultural drama in contemporary activism; insights from Sexuality & Gender Studies concerning scripted behaviour and LGBT+ and Q identity-formations, and, emerging research in Asexual Studies concerning asexual orientations, identities and socialised behaviours. The thesis emphasises the work of Goffmann (1971, 1974, 2017), Jasper (2008), Plummer (1994), Rubin (2011), Stallybrass and White (1986) and Tilly (1995) to analyse the presentation of the asexual activist self, the collective activist performances through which that self is embodied, and the interrelated asexual and Pride narratives that are contended. Through auto-ethnography it considers the researcher’s engagement with these contentious repertoires, as academic and participant-observer who is also an actor-activist, audience member and bystander. This analysis reveals a disconnect between the ongoing, framed scripting of Pride activism in the West and the emerging core-frames of asexual activist scripts; even as asexual activists seek alignment

Memory and resistance

Joseph DeLappe is a visual artist and activist. Images and texts in this feature detail a diversity of creative projects and actions that challenge and question our contemporary militaristic context. These works explore the intersections of art, technology, social engagement, and interventionist strategies. The included projects utilize digital processes, interruptive strategies, and participatory processes as tools for political, social, and creative transformation

Conservation and crime convergence? Situating the 2018 London Illegal Wildlife Trade Conference

The 2018 London Illegal Wildlife Trade (IWT) Conference was the fourth and biggest meeting on IWT convened at the initiative of the UK Government. Using a collaborative event ethnography, we examine the Conference as a site where key actors defined the problem of IWT as one of serious crime that needs to be addressed as such. We ask (a) how was IWT framed as serious crime, (b) how was this framing mobilized to promote particular policy responses, and (c) how did the framing and suggested responses reflect the privileging of elite voices? Answering these questions demonstrates the expanding ways in which thinking related to crime and policing are an increasingly forceful dynamic shaping conservation-related policy at the global level. We argue that the conservation-crime convergence on display at the 2018 London IWT Conference is characteristic of a conservation policy landscape that increasingly promotes and privileges responses to IWT that are based on legal and judicial reform, criminal investigations, intelligence gathering, and law enforcement technologies. Marginalized are those voices that seek to address the underlying drivers of IWT by promoting solutions rooted in sustainable livelihoods in source countries and global demand reduction. We suggest that political ecology of conservation and environmental crime would benefit from greater engagement with critical criminology, a discipline that critically interrogates the uneven power dynamics that shape ideas of crime, criminality, how they are politicized, and how they frame policy decisions. This would add further conceptual rigor to political ecological work that deconstructs conservation and environmental crime

Visual Distance Estimation in Static Compared to Moving Virtual Scenes

Visual motion is used to control direction and speed of self-motion and time-to-contact with an obstacle. In earlier work, we found that human subjects can discriminate between the distances of different visually simulated self-motions in a virtual scene. Distance indication in terms of an exocentric interval adjustment task, however, revealed linear correlationbetween perceived and indicated distances but with a profound distance underestimation. One possible explanation for this underestimation is the perception of visual space in virtual environments. Humans perceive visual space in natural scenes as curved, and distances are increasingly underestimated with increasing distance from the observer. Such spatial compression may also exist in our virtual environment. We therefore surveyed perceived visual space in a static virtual scene. We asked observers to compare two horizontal depth intervals, similar to experiments performed in natural space. Subjects had to indicate the size of one depth interval relative to a second interval. Our observers perceived visual space in the virtual environment as compressed, similar to the perception found in natural scenes. However, the nonlinear depth function we found can not explain the observed distance underestimation of visual simulated self-motions in the same environment.El movimiento visual se emplea en el control de la dirección y la velocidad de la autolocomoción y, también, para conocer el tiempo de contacto con un obstáculo. En trabajos anteriores encontramos que los observadores humanos pueden discriminar entre las distancias de diferentes auto-locomociones simuladas visualmente en una escena virtual. La indicación de la distancia mediante una tarea de ajuste de intervalo exocéntrico, sin embargo, reveló una correlación lineal entre las distancias percibidas y las indicadas, pero con una gran subestimación de la distancia. Una posible explicación de esta subestimación se basa en las características de la percepción visual del espacio en ambientes virtuales. En las escenas naturales los humanos percibimos el espacio visual como curvado, y las distancias se subestiman con el incremento de la separación respecto al observador. Esta compresión espacial también puede existir en nuestro ambiente virtual. Por ello, se decidió evaluar el espacio visual percibido en una escena estática virtual. Pedimos a los observadores que comparasen dos intervalos de profundidad horizontal, similares a experimentos llevados a cabo en el espacio natural. Los sujetos debían indicar el tamaño de un intervalo de profundidad con respecto a un segundo intervalo. Nuestros observadores percibían el espacio visual en el ambiente virtual como comprimido, similar a la percepción encontrada en escenas naturales. Sin embargo, la función no lineal de profundidad que ncontramos no puede explicar la subestimación observada de la distancia de las autolocomociones visuales simuladas en el mismo ambiente

Biological motion cues aid identification of self-motion from optic flow but not heading detection

© 2017 The Authors. When we move through the world, a pattern of expanding optic flow is generated on the retina. In completely rigid environments, this pattern signals one's direction of heading and is an important source of information for navigation. When we walk towards an oncoming person, the optic environment is not rigid, as the motion vectors generated by the other person represent a composite of that person's movement, his or her limb motion, and the observer's self-motion. Though this biological motion obfuscates the optic flow pattern, it also provides cues about the movement of other actors in the environment. It may be the case that the visual system takes advantage of these cues to simplify the decomposition of optic flow in the presence of other moving people. The current study sought to probe this possibility. In four experiments self-motion was simulated through an environment that was empty except for a single, walking point-light biological motion stimulus. We found that by using biological motion cues, observers were able to identify the presence of selfmotion despite the lack of stable scene information. However, when estimating heading based on these stimuli, the pattern of observer heading estimates could be approximately reproduced by computing the vector sum of the walker's translation and the stimulated selfmotion. This suggests that though biological motion can be used to disentangle self-motion in ambiguous situations, optic flow analysis does not use this information to derive heading estimates