5,426 research outputs found
Structured representations in the control of behavior cannot be so easily dismissed: a reply to Botvinick and Plaut (2006)
No full textM. Botvinick and D. C. Plaut (2006) argued that many of the criticisms of their earlier simple recurrent network (SRN) model of routine sequential action raised by R. P. Cooper and T. Shallice (2006) were criticisms of the specific implementation rather than criticisms of the underlying theory. Cooper and Shallice (2006) reject this assessment and raise concerns with several implementational adjustments that Botvinick and Plaut made to address their criticisms of the SRN account. Moreover, Botvinick and Plaut are questioned for not addressing potential interactions between their suggested implementational changes. Cooper and Shallice also reconsider the implications of the role of the training set in shaping the SRN model’s normal and error-prone behavior, the role of goals in their original interactive activation network model and routine behavior more generally, and the relation between the putative routine and nonroutine action control systems within the 2 models
Tool use and related errors in ideational apraxia: The quantitative simulation of patient error profiles
No full textThe behaviour of ideational apraxic patients on simple tasks involving multiple objects is typically marked by a variety of errors. While some of these errors concern the sequential organisation of action through time, many relate to the misuse of, or failure to use, necessary or appropriate tools. In this paper we apply the computational model of Cooper & Shallice (2000) to five standard multiple object tasks used in clinical assessment and demonstrate how, when lesioned, the model can account for the error profiles of two ideational apraxic patients discussed by Rumiati et al. (2001). Application of the model to the multiple object tasks demonstrates the generality of the model, while the account of the error profiles extends previous work (Cooper et al., 2005) in which ideational apraxia was argued to arise from a generalised disturbance of object representations that are held to trigger action schemas
Hierarchical schemas and goals in the control of sequential behavior
No full textTraditional accounts of sequential behavior assume that schemas and goals play a causal role in the control of behavior. In contrast, M. Botvinick and D. C. Plaut (2004) argued that, at least in routine behavior, schemas and goals are epiphenomenal. The authors evaluate the Botvinick and Plaut account by contrasting the simple recurrent network model of Botvinick and Plaut with their own more traditional hierarchically structured interactive activation model (R. P. Cooper & T. Shallice, 2000). The authors present a range of arguments and additional simulations that demonstrate theoretical and empirical difficulties for both Botvinick and Plaut’s model and their theoretical position. The authors conclude that explicit hierarchically organized and causally efficacious schema and goal representations are required to provide an adequate account of the flexibility of sequential behavior
Wavelength tunable 10-GHz 3-ps pulse source using a dispersion decreasing fiber-based nonlinear optical loop mirror
No full textWe experimentally demonstrate the use of a dispersion decreasing fiber (DDF)-based nonlinear optical loop mirror (NOLM) for the generation of wavelength tunable soliton-like pulses at a repetition rate of 10 GHz. We compress ~12 ps Gaussian pulses from an electro-absorption modulator (EAM) (followed by 125 m of DCF for preliminary linear dispersion compensation) into 3 ps pedestal-free pulses using both high-order soliton compression and nonlinear switching effects within an 8.5 km DDF-based loop mirror. The output pulses from the DDF-based NOLM show considerable pedestal reduction compared to those obtained by directly compressing the EAM seed pulses via a single passage through the DDF. Wavelength tuning of the compressed pulses over a ~15 nm bandwidth (from 1541 to 1556 nm) is demonstrated without a significant increase in pulse duration or degradation in pulse quality
The simulation of action disorganisation in complex activities of daily living
No full textAction selection in everyday goal-directed tasks of moderate complexity is known to be subject to breakdown following extensive frontal brain injury. A model of action selection in such tasks is presented and used to explore three hypotheses concerning the origins of action disorganisation: that it is a consequence of reduced top-down excitation within a hierarchical action schema network coupled with increased bottom-up triggering of schemas from environmental sources, that it is a more general disturbance of schema activation modelled by excessive noise in the schema network, and that it results from a general disturbance of the triggering of schemas by object representations. Results suggest that the action disorganisation syndrome is best accounted for by a general disturbance to schema activation, while altering the balance between top-down and bottom-up activation provides an account of a related disorder - utilisation behaviour. It is further suggested that ideational apraxia (which may result from lesions to left temporoparietal areas and which has similar behavioural consequences to action disorganisation syndrome on tasks of moderate complexity) is a consequence of a generalised disturbance of the triggering of schemas by object representations. Several predictions regarding differences between action disorganisation syndrome and ideational apraxia that follow from this interpretation are detailed
A computational model of action resonance and its modulation by emotional stimulation
No full textRecent research has shown that stimulus–response compatibility (SRC) effects can be modulated by the emotional state of the participant and, more specifically, that the SRC effect is larger when aversive emotional stimulation precedes the seen movement [Rumiati, R. I. & Grecucci, A. (submitted for publication). On the emotional modulation of action]. In the present study, we propose that this effect arises from four assumptions: First, that the cortical representations subserving observation and execution of the same actions overlap and resonate; second, that graded persistence of activation due to observed movement facilitates subsequent movement execution; third, that movement representations that are similar but different compete for activation; and fourth, that aversive emotional states enhance the processing of events. By means of a set of simulations, we demonstrate that each of these assumptions plays a critical role in capturing the compatibility effect and its emotional modulation. We further employ the model to clarify the debate between synergistic and competitive views of cognition/emotion interactions, and demonstrate how emotionally-driven stimulus–response compatibility effects may be modulated by task demands, thus offering a possible resolution to the long-standing debate between synergistic and competitive interactions between emotion and cognition
Extending the contention scheduling model of routine action selection: The Wisconsin Card Sorting Task and frontal dysfunction
No full textWe extend a previously developed model of routine action
selection by incorporating functional components to support
behaviour in a simple non-routine task – sorting cards
according to a rule that must be discovered by the subject. A
minimal extension to the previous model, consisting of an
activation-based working memory/inference system in which
evidence is incorporated by simply exciting or inhibiting
relevant rule nodes, is demonstrated to be capable of
capturing basic performance on the task. The task is
commonly used in assessing frontal brain injury, and the
extended model is further shown to be capable of capturing
the gross behavioural characteristics of frontal patients.
However, it is argued that a purely activation-based working
memory cannot capture the requirements of more complex
tasks. The paper thereby demonstrates 1) how the basic
routine action model might be extended to more complex
behaviours, but 2) that such behaviours require more than
simple activation-based memory processes to structure nonroutine
behaviour over time
The roles of functional neuroimaging and cognitive neuropsychology in the development of cognitive theory: a reply to Coltheart
No full textThis is a rejoinder in response to the book review by Max Coltheart on the book The Organization of Mind, edited by Tim Shallice and Richard P. Cooper, Oxford: Oxford University Press, 2011, pp. 608. ISBN 978-0-19-957924-2
Player agency in interactive narrative: audience, actor & author
No full textThe question motivating this review paper is, how can
computer-based interactive narrative be used as a constructivist learn-
ing activity? The paper proposes that player agency can be used to
link interactive narrative to learner agency in constructivist theory,
and to classify approaches to interactive narrative. The traditional
question driving research in interactive narrative is, ‘how can an in-
teractive narrative deal with a high degree of player agency, while
maintaining a coherent and well-formed narrative?’ This question
derives from an Aristotelian approach to interactive narrative that,
as the question shows, is inherently antagonistic to player agency.
Within this approach, player agency must be restricted and manip-
ulated to maintain the narrative. Two alternative approaches based
on Brecht’s Epic Theatre and Boal’s Theatre of the Oppressed are
reviewed. If a Boalian approach to interactive narrative is taken the
conflict between narrative and player agency dissolves. The question
that emerges from this approach is quite different from the traditional
question above, and presents a more useful approach to applying in-
teractive narrative as a constructivist learning activity
Direct Picosecond Measurement of Photoinduced Cooper Pair Breaking in Lead
No full textWe report on a direct kinetic measurement of Cooper-pair breaking in superconducting lead. A 100-fs pulse of visible light was used to excite a thin-film lead sample, while the Cooper-pair density was optically probed using an ultrashort pulse of broadband far-infrared radiation. Subsequent to the absorption of the visible light, a rapid (ps) change in the far-infrared optical transmission was observed, corresponding to the breaking of Cooper pairs and the collapse of the superconducting gap
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