A Self-Organizing Neural Model of Motor Equivalent Reaching and Tool Use by a Multijoint Arm

This paper describes a self-organizing neural model for eye-hand coordination. Called the DIRECT model, it embodies a solution of the classical motor equivalence problem. Motor equivalence computations allow humans and other animals to flexibly employ an arm with more degrees of freedom than the space in which it moves to carry out spatially defined tasks under conditions that may require novel joint configurations. During a motor babbling phase, the model endogenously generates movement commands that activate the correlated visual, spatial, and motor information that are used to learn its internal coordinate transformations. After learning occurs, the model is capable of controlling reaching movements of the arm to prescribed spatial targets using many different combinations of joints. When allowed visual feedback, the model can automatically perform, without additional learning, reaches with tools of variable lengths, with clamped joints, with distortions of visual input by a prism, and with unexpected perturbations. These compensatory computations occur within a single accurate reaching movement. No corrective movements are needed. Blind reaches using internal feedback have also been simulated. The model achieves its competence by transforming visual information about target position and end effector position in 3-D space into a body-centered spatial representation of the direction in 3-D space that the end effector must move to contact the target. The spatial direction vector is adaptively transformed into a motor direction vector, which represents the joint rotations that move the end effector in the desired spatial direction from the present arm configuration. Properties of the model are compared with psychophysical data on human reaching movements, neurophysiological data on the tuning curves of neurons in the monkey motor cortex, and alternative models of movement control.National Science Foundation (IRI 90-24877); Office of Naval Research (N00014-92-J-1309); Air Force Office of Scientific Research (F49620-92-J-0499); National Science Foundation (IRI 90-24877

A Self-Organizing Neural Network for Learning a Body-Centered Invariant Representation of 3-D Target Position

This paper describes a self-organizing neural network that rapidly learns a body-centered representation of 3-D target positions. This representation remains invariant under head and eye movements, and is a key component of sensory-motor systems for producing motor equivalent reaches to targets (Bullock, Grossberg, and Guenther, 1993).National Science Foundation (IRI-87-16960, IRI-90-24877); Air Force Office of Scientific Research (F49620-92-J-0499

Deregulation of conveyancing markets in England and Wales

There has been much concern in recent years with whether the ‘privilege’ of self- regulation accorded to the professions works for or against the public interest (Federal Trade Commission, 1984; Monopolies and Mergers Commission, 1970, 1976a and 1976b; Department of Trade and Industry, 1989; Courts and Legal Services Act, 1990). Ogus (1993) argues that ‘Self-regulation has had a bad press’ and that ‘most of this criticism is well-founded in relation to some forms of self- regulation’. Economists have been, traditionally, highly critical of many aspects of professional self-regulation.2 More recently, there has been a greater awareness of the informational asymmetry inherent in professional markets which demands some protection for the (infrequent) consumer of personal professional services (see, for example, Dingwall and Fenn (1987)). Commentators have identified three principal instruments of such selfregulators which work against the public interest: (1) restrictions on entry; (2) restrictions on fee competition; and (3) restrictions on advertising and other means of promoting a competitive process within the profession.

Securing Repo: Counterparty Risk and Collateral Supply Effects in the Tri-Party Repo Market

I examine the co-variance between tri-party repurchase agreement (repo) spreads and proxies for collateral values and counterparty risk. Since the Global Financial Crisis of 2008 (GFC), the Federal Reserve (Fed) has taken measures to mitigate repo market instability. These measures have collectively placed the Fed astride repo markets as ongoing borrower, lender and purchaser of US Treasury and Agency securities. By analyzing the relationships between repo spreads, the US 10-year yield and the TED spread, I assess the effectiveness of Fed measures to mitigate repo market instability. Using multiple breakpoint Bai-Perron regression and Markov Switching tests, I find that these measures have been effective, with accompanying unintended consequences

Why Plea-Bargaining Fails to Achieve Results in So Many Criminal Justice Systems: A New Framework for Assessment

The myth of American exceptionalism in the matter of plea-bargaining is certainly by now quite untrue. In addition to forming an important part of criminal procedure in the United Kingdom, plea-bargaining has been transplanted to several civil law countries such as France and Italy. Informal versions, based on non-trial settlement, have been observed in Germany, Belgium, the Netherlands, and around the world. The Law and Economics literature on plea-bargaining views it as an efficient instrument of criminal procedure because it reduces enforcement costs (for both parties) and allows the prosecutor to concentrate on more meritorious cases. Yet the success of transplants relies on the existence of appropriate incentives, and the detailed study of the Italian experience provides a good indication that the traditional inquisitorial system might not generate such incentives. Instead, this article offers a new theory emphasizing the role of the prosecutor and that of the defence counsel. We argue that the incentives of the prosecutor and those of the defence counsellor are determinants of the success or failure of plea-bargaining. We are sceptical that plea-bargaining can lead to or is consistent with the desirable outcome in many circumstances. In particular, a major implication of our analysis is that the comparative efficiency of plea-bargaining to a larger extent depends on the possibility of a legal system to address the multiple principle-agent problems in criminal litigation

Why Plea-Bargaining Fails to Achieve Results in So Many Criminal Justice Systems: A New Framework for Assessment

The myth of American exceptionalism in the matter of plea-bargaining is certainly by now quite untrue. In addition to forming an important part of criminal procedure in the United Kingdom, plea-bargaining has been transplanted to several civil law countries such as France and Italy. Informal versions, based on non-trial settlement, have been observed in Germany, Belgium, the Netherlands, and around the world. The Law and Economics literature on plea-bargaining views it as an efficient instrument of criminal procedure because it reduces enforcement costs (for both parties) and allows the prosecutor to concentrate on more meritorious cases. Yet the success of transplants relies on the existence of appropriate incentives, and the detailed study of the Italian experience provides a good indication that the traditional inquisitorial system might not generate such incentives. Instead, this article offers a new theory emphasizing the role of the prosecutor and that of the defence counsel. We argue that the incentives of the prosecutor and those of the defence counsellor are determinants of the success or failure of plea-bargaining. We are sceptical that plea-bargaining can lead to or is consistent with the desirable outcome in many circumstances. In particular, a major implication of our analysis is that the comparative efficiency of plea-bargaining to a larger extent depends on the possibility of a legal system to address the multiple principle-agent problems in criminal litigation

Indianola : Song

https://digitalcommons.library.umaine.edu/mmb-vp/1889/thumbnail.jp