Towards the Integration of Perceptual Organization and Visual Attention: The Inferential Attentional Allocation Model. Technical Report 2001-08

Object-based models of visual attention purport to explain why it is easier to process information within one object or perceptual group than across two or more groups. Perceptual groups are generally defined in terms of Gestalt grouping principles. These models of attention have been used to explain the phenomenon of cognitive tunneling within Heads-Up Displays (HUDs), on the assumption that the symbology of a Heads-Up Display (HUD) in a cockpit forms a single perceptual group and the outside scene forms another. Despite extensive empirical support, object-based models have various shortcomings. In particular, the use of Gestalt grouping principles to define the notion of objects does not allow for an operational measure of what an object is to the visual system. Also, the Gestalt principles do not allow for a systematic distinction between spatial and object-based mechanisms of attention. Finally, it is generally assumed that Gestalt grouping occurs preattentively, whereas there is evidence that perceptual grouping requires attentional resources. The proposed line of research aims to develop an account of object-based attention that does not rely on these premises. Rather, it is assumed that the cost of dividing attention between objects reflects the cost of perceptual organization itself. A qualitative model based on this assumption, called the “Inferential Attentional Allocation Model,” is given. A number of experiments are proposed to test key aspects of the model, in particular the effects of motion and top-down knowledge on perceptual organization and attention. It is expected that the results will facilitate the development of a quantitative model of object-based attention, based on a computational characterization of perceptual organization as inference to the best explanation. Finally, the implications of this research for HUDs with dynamic elements are discussed

Integrating Perceptual Organization and Attention: A New Model for Object-Based Attention. Technical Report 2002-07

Recent research shows that, under certain conditions, visual attention is object-based. That is, attention preferentially selects objects in the visual field. These objects are processed, culminating in object recognition. On this formulation, the objects selected by attention are perceptual groups determined by the principles of perceptual organization of Gestalt psychology. These groups are formed independently of attentional processes and conceptual knowledge. This view is not consistent with available data about the visual system, which shows that perceptual organization is sensitive to conceptual information, depends on attentional processes, and infers representations that best explain the visual stimulus. Here, I propose a new account of visual attention that aims to correct these limitations of the Gestalt-based formulation. The nature of the object representations underlying perceptual and attentional mechanisms is discussed. It is proposed that attention and perception interact in an iterative process wherein constraints imposed both by the visual stimulus and an observer’s cognitive set determine the “objects” to which attention is allocated. Thus, visual attention is object based precisely because it is intricately involved in perceptual organization, and not because it selects the output of perceptual organization, as is generally claimed. Experimental results that support the claim that attention influences perceptual organization are reviewed. Finally, the implications for human factors research and the metaphysics of everyday objects are discussed

Objects, Pilots, and the Act of Attending: A Conative Account of Visual Attention. Technical Report 2003-04

Current research on visual attention is dominated by the object-based thesis, whereby visual input is organized into Gestalt groupings, and attention operates over these groupings. On this view, attention is more effectively allocated to a single object than to two or more. This theory is supported by experimental data, and has some ecological validity from research on Heads-Up Displays (HUDs). This research shows that under certain conditions pilots’ attention becomes fixated on one object (the HUD) at the expense of monitoring events from another object (the outside scene). This phenomenon, called “cognitive tunnelling,” cannot be explained by the spatial parameters of attention, and thus is consistent with the object-based thesis. Despite the evidence for object-based attention, the conceptual foundations of the theory are questionable. Perceptual organization is an inference-based process, rather than one based on Gestalt principles. Also, evidence shows that conative factors – motivations, goals, needs – play important roles in what people perceive and attend to as objects. In the present research, a series of seven experiments was carried out to examine attentional mechanisms underlying HUD use. These experiments show that attentional strategies, task demands and the locus of control of the display strongly influence on what pilots focus attention, and to what degree. On the basis of these results, and of a critical review of the research literature on attention, a conative model of attention is proposed. On this model, attention is an active process wherein the visual system uses visual objects as tools for directing attention according to an observer’s background knowledge, intentions, and task context. Observers focus on what is relevant to their tasks and needs, subject to perceptual constraints. According to this model, task demands and pilot training determine to what degree pilots “tunnel” their attention onto a HUD or its sub-parts. Wider implications for human factors research on HUD use, and for the study of cognition in general, are discussed

Design and implementation of a distributed synchronization scheduler for a multimedia news-on-demand application.

The CITR News-On-Demand is a system whose architecture follows the client-server paradigm: a distributed database provides multimedia news articles to users by means of a client application. Due to practical considerations, the synchronization system used in this prototype is a centralized one, in which the client application bears the whole burden of scheduling data retrieval and presentation. While this is simpler to implement, it makes more demands on the client's resources than a distributed system. Furthermore, research into the issue suggests that a distributed system would be more efficient at preventing synchronization errors. This thesis shows how the synchronization system of the News-on-Demand prototype can be re-engineered to make it distributed. It first considers the theoretical concepts behind synchronization systems and provides a framework for doing so simply and in a manner which can be systematically applied to any system. The News-on-Demand prototype is then studied using this framework, and its shortcomings as regard synchronization are discussed. Research at the MCRLab into distributed synchronization systems is also studied with this framework, and it is shown how this research can be applied to the News-on-Demand system. With this, a distributed synchronization system for the CITR project is designed and implemented, which integrates the distributed synchronization concepts into the existing system. The pseudo-code and the data structures of the new system are given and discussed

Lowered Situation Awareness When Using a Helmet-Mounted Head-Up Display (HUD) in a Simulated Rotary-Wing Aircraft

Head-up displays (HUDs) have been shown to facilitate pilot performance in specific tasks such as controlling flight path and altitude. However, results from a number of simulator-based studies suggest that HUDs may decrease pilot situation awareness (SA) in tasks that require continuous monitoring of information in the environment. In extreme cases, HUDs have lowered SA to the extent that pilots may fail to detect potentially critical discrete events in the environment. Most research on HUDs has used fixed-panel displays. The present research examined the impact of a helmet-mounted display (HMD) HUD on pilot SA