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We present a schema-based model of a classicneuropsychological task, the Wisconsin Card Sorting Task(WCST), where competition between motor and cognitiveschemas is resolved using a variation of a neuroanatomicallydetailed model of the basal ganglia (Gurney et al., 2001). Weshow that the model achieves a good fit with existing data atthe group level, and correctly identifies two distinct cognitivemechanisms held to underlie two distinct types of error.However, at the individual level, the correlations amongstother error types produced by the model differ from thoseobserved in the human data. To address this, we clusterparticipant performance into distinct groups and show, byfitting each group separately, how the model can account forthe empirically observed correlations between error types.Methodologically, this demonstrates the importance ofmodelling participant performance at the sub-group orindividual level, rather than modelling group performance.We also discuss implications of the model for the WCSTperformance of elderly participants and Parkinson’s patients.

It is argued that event perception and routine sequential action production share a range of characteristics (e.g., similar levels of automaticity, the involvement of sequentially and hierarchically organized schemata, and the coupled operation of predictive and monitoring processes). With this in mind, and in an effort to develop a mechanistic account of event perception, we consider how an existing model of routine sequential action production might be applied in the domain of event perception. We focus the discussion on the multiple roles of prediction in the two domains, and we consider the implications of the application of the model of action production to event perception and for sequential processing more generally. Cooper argues for the use of event representations in action execution, as well as in event perception, and foresees multiple roles for prediction in each case. He argues for strong similarities between perceptual and motor processing of events, and considers how the 'contention scheduling' model of action execution could be redeployed for event perception. [ABSTRACT FROM AUTHOR]

This paper reports on an exploratory study which set out to explore the role of compatible and incompatible transactions, assimilation, accommodation and contention scheduling in teams by applying schema theory to team communications. Schema theory and in particular the notions of contention scheduling, schema-driven errors and the perceptual cycle model, supports the ideas presented in the distributed situation awareness approach by explaining the way in which previous experience and knowledge amassed by each team member shape their interactions with the world. Understanding the role of schemas and the perceptual cycle model is necessary if the phenomenon of situation awareness is to be exploited positively in the organisation of teams, work and design of socio-technical systems. The findings indicate that team members influence each other's schemata and that where opposing ideas, or schemata, with regard to what the team ought to do, a process of contention scheduling was applied to establish agreement on a common goal. Team members' schemata were adapted by the mechanisms of assimilation and accommodation. Schemata were altered as a result of interaction between team members, e.g. their transactions, where each team member tested their ideas on the wider team, thus further developing their understanding of the external environment. These findings indicate that the perceptual cycle model can be scaled up to explain team's dynamic exploration of, interaction with and adaptation to their environment. Schemata should therefore be explored along with the transactional SA and compatible SA in explaining the emergence of distributed SA in teams. [ABSTRACT FROM AUTHOR]

We report two experiments in which errors and interaction latencies were recorded during routinization of hierarchically structured computer-based tasks. Experiment 1 demonstrates that action selection is slowed at subtask transitions, especially when selecting lower frequency actions. This frequency effect is compounded by concurrent performance of a secondary, attentionally demanding, task. Experiment 2 replicates these results in a more complex task and further demonstrates that the effects are reduced by experience. Several other factors were also found to affect latencies, including the availability of an external disambiguation cue and the temporal distance over which task context needs to be internally maintained. The results support a "dual-systems" account of action selection in which a "routine" system, sensitive to frequency, context, and experience, is selectively modulated by an attentionally demanding "nonroutine" system. [ABSTRACT FROM AUTHOR]

Networks of workstations are a dominant force in the distributed computing arena, due primarily to the excellent price/performance ratio of such systems when compared to traditionally massively parallel architectures. It is therefore critical to develop programming languages and environments that can help harness the raw computational power available on these systems. In this article, we present JavaNOW (Java on Networks of Workstations), a Java-based framework for parallel programming on networks of workstations. It creates a virtual parallel machine similar to the MPI (Message Passing Interface) model, and provides distributed associative shared memory similar to the Linda memory model but with a richer set of primitive operations. JavaNOW provides a simple yet powerful framework for performing computation on networks of workstations. In addition to the Linda memory model, it provides for shared objects, implicit multithreading, implicit synchronization, object dataflow, and collective communications similar to those defined in MPI. JavaNOW is also a component of the Computational Neighborhood, a Java-enabled suite of services for desktop computational sharing. The intent of JavaNOW is to present an environment for parallel computing that is both expressive and reliable and ultimately can deliver good to excellent performance. As JavaNOW is a work in progress, this article emphasizes the expressive potential of the JavaNOW environment and presents preliminary performance results only. Copyright © 2000 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]