The dynamics of embodiment: a field theory of infant perseverative reaching

The overall goal of this target article is to demonstrate a mechanism for an embodied cognition. The particular vehicle is a much-studied, but still widely debated phenomenon seen in 7-12 month-old-infants. In Piaget's classic "A-not-B error," infants who have successfully uncovered a toy at location "A" continue to reach to that location even after they watch the toy hidden in a nearby location "B." Here, we question the traditional explanations of the error as an indicator of infants' concepts of objects or other static mental structures. Instead, we demonstrate that the A-not-B error and its previously puzzling contextual variations can be understood by the coupled dynamics of the ordinary processes of goal-directed actions: looking, planning, reaching, and remembering. We offer a formal dynamic theory and model based on cognitive embodiment that both simulates the known A-not-B effects and offers novel predictions that match new experimental results. The demonstration supports an embodied view by casting the mental events involved in perception, planning, deciding, and remembering in the same analogic dynamic language as that used to describe bodily movement, so that they may be continuously meshed. We maintain that this mesh is a pre-eminently cognitive act of "knowing" not only in infancy but also in everyday activities throughout the life span.     

On the ultra-high-strain rate shock deformation in copper single crystals: multiscale dislocation dynamics simulations

Multiscale dislocation dynamics plasticity (MDDP) calculations are carried out to simulate the mechanical response of copper single crystals that have undergone shock loading at high strain rates ranging from 1?×?10⁶ to 1?×?10¹⁰?s^?1. Plasticity mechanisms associated with both the activation of pre-existing dislocation sources and homogeneous nucleation of glide loops are considered. Our results show that there is a threshold strain rate of 10⁸?s^?1 at which the deformation mechanism changes from source activation to homogeneous nucleation. It is also illustrated that the pressure dependence on strain rate follows a one-fourth power law up to 10⁸?s^?1 beyond which the relationship assumes a one-half power law. The MDDP computations are in good agreement with recent experimental findings and compare well with the predictions of several dislocation-based continuum models.     

Moving to higher ground: The dynamic field theory and the dynamics of visual cognition

In the present report, we describe a new dynamic field theory that captures the dynamics of visuo-spatial cognition. This theory grew out of the dynamic systems approach to motor control and development, and is grounded in neural principles. The initial application of dynamic field theory to issues in visuo-spatial cognition extended concepts of the motor approach to decision making in a sensori-motor context, and, more recently, to the dynamics of spatial cognition. Here we extend these concepts still further to address topics in visual cognition, including visual working memory for non-spatial object properties, the processes that underlie change detection, and the ‘binding problem’ in vision. In each case, we demonstrate that the general principles of the dynamic field approach can unify findings in the literature and generate novel predictions. We contend that the application of these concepts to visual cognition avoids the pitfalls of reductionist approaches in cognitive science, and points toward a formal integration of brains, bodies, and behavior.     

Dislocation multiplication in bcc molybdenum: A dislocation dynamics simulation

Plastic deformation of Mo single crystals is examined by direct simulation of dislocation dynamics under stress. Initial dislocation populations are made to mimic real dislocation microstructures observed in transmission electron microscopy cross-sections of pure annealed Mo single crystals. No a priori sources for dislocation multiplication are introduced, and yet multiplication takes place through a sequence involving aggregation of grown-in superjogs, bowing of screw dislocation segments and fast lateral motion of edge segments, producing a large number of elongated loops and a characteristic cross-grid pattern of screw dislocations.     

The displacement field of a rectangular Volterra dislocation loop

The displacement field of a rectangular Volterra dislocation loop having three non-zero Burgers vector components is obtained in an analytical closed form. The solution is obtained via integrating the Burgers equation for the displacement field of any closed dislocation curve and is expressed in a relatively compact form. The current solution has utility in a number of problems including dislocation-particle interaction problems, where the boundary condition involved imposes certain restrictions on the displacements in the medium, and modelling of cracks of arbitrary shapes. The solution is also useful in benchmarking newly emerging dislocation dynamics codes which discretize a curved dislocation line in some form or another. Several verification steps of the solution correctness are made including a comparison with the displacement and stress fields of a circular Volterra dislocation loop of equal Burgers vector and comparable size.     

Social comparison: The end of a theory and the emergence of a field

The past and current states of research on social comparison are reviewed with regard to a series of major theoretical developments that have occurred in the past 5 decades. These are, in chronological order: (1) classic social comparison theory, (2) fear-affiliation theory, (3) downward comparison theory, (4) social comparison as social cognition, and (5) individual differences in social comparison. In addition, we discuss a number of expansions of research on social comparison as they are currently occurring, and we outline what we see as likely and desirable future directions, including an expansion of areas, methods, and conceptualizations, as well as a stronger focus on cognitive, neuroscientific, and evolutionary aspects of social comparison.     

Modelling of irradiation-induced hardening in metals using dislocation dynamics

A new simulation technique (three-dimensional dislocation dynamics) enabling the capture of a hardening effect in metals due to irradiation is reported. When bombarded with high-energy particles, metals accrue internal damage. In irradiated Pd, for example, damage takes the form of interstitial loops. Such loops are nano-sized and typically have a high number density. The stress field of a loop is given from dislocation theory. It is shown here the hardening is due to the elastic interaction of gliding dislocations with a high number of spatially dispersed interstitial loops. Results are found to correlate well with experiments.     

Model theory of deduction: a unified computational approach

One of the most debated questions in psychology and cognitive science is the nature and the functioning of the mental processes involved in deductive reasoning. However, all existing theories refer to a specific deductive domain, like syllogistic, propositional or relational reasoning.
Our goal is to unify the main types of deductive reasoning into a single set of basic procedures. In particular, we bring together the microtheories developed from a mental models perspective in a single theory, for which we provide a formal foundation. We validate the theory through a computational model (UNICORE) which allows fine-grained predictions of subjects' performance in different reasoning domains.
The performance of the model is tested against the performance of experimental subjects—as reported in the relevant literature—in the three areas of syllogistic, relational and propositional reasoning. The computational model proves to be a satisfactory artificial subject, reproducing both correct and erroneous performance of the human subjects. Moreover, we introduce a developmental trend in the program, in order to simulate the performance of subjects of different ages, ranging from children (3–6) to adolescents (8–12) to adults (>21). The simulation model performs similarly to the subjects of different ages.
Our conclusion is that the validity of the mental model approach is confirmed for the deductive reasoning domain, and that it is possible to devise a unique mechanism able to deal with the specific subareas. The proposed computational model (UNICORE) represents such a unifying structure.     

Toward a generative theory of the therapeutic field

In the various models of family therapy, family systems are described as being patterned and programmed in their operations and development. The regularities and patterns found in family life are believed to be the expression of a program that determines the behavior of the family system and each of its members. Therapists holding this view will use "programming methods" in order to map family phenomena, and therapeutic work will consist of disrupting the problematic sequences in a deterministic way. However, if we take into consideration the impossibility of always linking inputs and outputs and the inability to evaluate consistently the behaviors in a system, problems associated with indeterminancy appear. Under such conditions, it may be impossible for therapists to formulate programs of family functioning. Therefore, we have operationalized a set of methodological principles that can be applied in such conditions. In this article we present the theoretical and practical implications for the field of therapy of "nonprogramming methods." A videotaped session is analyzed in order to show the application of the nonprogramming methods in clinical practice.     

Learning as change of coordination dynamics: theory and experiment

Learning of coordination patterns was investigated theoretically from the point of view of a dynamic theory of biological coordination and with reference to recent experiments on the learning of relative timing patterns. The theory is based on theoretical and experimental work showing that coordinated movement is characterized not only by the actually performed pattern of coordination but by an entire dynamics of coordination. Theoretically, such dynamics are captured as equations of motion of relevant collective variables. Experimentally, signatures of these underlying dynamics can be found in the temporal stability of coordination patterns, which can be assessed through various stability measures as well as through processes of pattern change. We argue that not only intrinsic coordination tendencies, but also specific behavioral requirements, be they perceived, memorized, or intended, must be expressed in terms of such dynamics. The concept of behavioral information captures such requirements as part of the coordination dynamics. We expound two hypotheses on the nature of learning in this framework. First, we assume that at each point during the learning process the system is governed by a well-defined coordination dynamics. This equation of motion evolves with learning so as to acquire an attractor solution near the to-be-learned pattern. Second, we hypothesize that this change of the coordination dynamics, captured by the time course of memorized behavioral information, can itself be ascribed to an additional layer of dynamics, the slower learning dynamics. Testable consequences of these views are discussed in the light of recent experimental findings on the learning of a relative phase in rhythmic movement: (a) Learning affects dynamic properties of performed coordination patterns, in particular, their stability; (b) the change of the coordination dynamics due to learning leads to specific changes of behavior also under conditions other than the learned condition, namely, to systematic deviation toward the learned patterns; (c) learning may lead to instabilities in the coordination behavior if initial and learned performance differ sufficiently; and (d) the dynamic properties of the performed coordination patterns are distinct on the two time scales of learning and of performance.     

Multialternative decision field theory: a dynamic connectionist model of decision making

The authors interpret decision field theory (J. R. Busemeyer & J. T. Townsend, 1993) as a connectionist network and extend it to accommodate multialternative preferential choice situations. This article shows that the classic weighted additive utility model (see R. L. Keeney & H. Raiffa, 1976) and the classic Thurstone preferential choice model (see L. L. Thurstone, 1959) are special cases of this new multialternative decision field theory (MDFT), which also can emulate the search process of the popular elimination by aspects (EBA) model (see A. Tversky, 1969). The new theory is unique in its ability to explain several central empirical results found in the multialternative preference literature with a common set of principles. These empirical results include the similarity effect, the attraction effect, and the compromise effect, and the complex interactions among these three effects. The dynamic nature of the model also implies strong testable predictions concerning the moderating effect of time pressure on these three effects.     

The role of beliefs in goal dynamics: prolegomena to a constructive theory of intentions

In this article we strive to provide a detailed and principled analysis of the role of beliefs in goal processing—that is, the cognitive transition that leads from a mere desire to a proper intention. The resulting model of belief-based goal processing has also relevant consequences for the analysis of intentions, and constitutes the necessary core of a constructive theory of intentions, i.e. a framework that not only analyzes what an intention is, but also explains how it becomes what it is. We discuss similarities and differences between our approach and other standard accounts of intention, in particular Bratman’s planning theory. The aim here is to question and refine the conceptual foundations of many theories of intentional action: as a consequence, although our analysis is not formal in itself, it is ultimately meant to have deep consequences for formal models of intentional agency.