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