The spring-like behaviour of a joint following a sudden change of torque is partly a result of the elastic properties of tendons. A large fall in a muscle with a long tendon may be accompanied by tendon recoil causing joint movements as large as 20°.

Mealey's interesting interpretation of sociopathy is based on an inappropriate two-person game model. A multiperson, compound game version of Chicken would be more suitable, because a population engaging in random pairwise interactions with that structure would evolve to an equilibrium in which a fixed proportion of strategic choices was exploitative, antisocial, and risky, as required by Mealey's interpretation.

In interpreting measurements of brain processes it is necessary to make the model used explicit. A concept such as attention cannot be used in the description of brain activities without a model of the relation of mental and neural processes.

A pair of arguments suggests that self-control is not properly conceptualized on the pattern/act/preference model Rachlin proposes. The first concerns the irrational following of personal rules. The second concerns scenarios in which behavioral patterns an agent deems good come into conflict.

Mealey's evolutionary reasoning is logically flawed. Furthermore, the evidence presented in favor of a genetic contribution to the causation of sociopathy is overinterpreted. Given the potentially large societal impact of sociobiological speculation on the roots of criminality, more-than-usual caution in interpreting data is called for.

Two aspects of the target article, (1) the extension of the equilibrium point theory to multi-joint movements, and (2) the consequence that the EMG pattern is not directly controlled by the central nervous system (CNS), are discussed in light of the experiments on upper trunk bending in humans. The principle component kinematic analysis and the analysis of the EMG data, obtained under microgravity and additional loading conditions, support the application of Feldman and Levin's for multi-joint pointing movement to equilibrium control during upper trunk movement.

You cannot overcome addiction or impulsiveness through abstract patterns alone. They show you the way to go, but do not fuel the effort. Some further variable is needed in the equation, some internal force or motivational mechanism, whatever its nature. Overlooking this leads to a neo-Socratic exaggeration of the role of cognition in selfcontrol.

Images of mind marks a new era in human cognitive neuroscience. Despite the difficult conceptual problems associated with using group-averaged data and paired subtractions, human PET images converge well with existing data from other areas of cognitive neuroscience while opening up new theoretical and experimental possibilities. However, greater attention to individual differences might prove necessary in the study of culturally driven adaptations such as literacy.

We emphasize the relevance to cognitive psychology of Feldman and Levin's theoretical position. Traditional views of motor control have failed to clearly separate “production control” at the level of motor command, based on task-independent CV (control variables), from intentional “product control” based on task-dependent parameters. Because F&L's approach concentrates on the first process (trajectory formation), it can distinguish the product control stage.

As more criminals are imprisoned, other individuals change their behavior to replace them, as predicted by the “floating niche” theory of strategic behavior. The physiological correlates of sociopathy suggest that research in cognitive neuroscience can lead toward a solution. Promising pathways include building upon current knowledge of self-deceit, the independence of positive and negative emotions, the lateralization of risk and caution, and the conditions promoting prosocial behavior.

Self-control is in the eye of the beholder. However, we speak of ”self-control” if a person has come to think conscious thoughts that change the motivational value of stimuli in the outside world. It is claimed that conscious thinking, and not habits bordering on compulsion, is behind self-control.

A methodological problem may distort the implications derived from the metabolism scans of the brain, but Posner & Raichle may have found neural networks which underlie the analytical and synthetical hemispheric data processing mechanism. This methodological problem is that a large regional consumption of energy, detected by the PET technique, is not necessarily related to more data processing. It may be related to the inefficiency of the neural system at this region.

The conservative strategy proposed by the authors suggests a solution of the degrees-of-freedom problem of the controller. However, several simple motor control tasks cannot be explained by this strategy. A nonconservative strategy, in which more parameters of the control signal vary, can account for these simple motor tasks. However, the simplicity that distinguishes the proposed model from many others is lost.

Encoding articulate speech is widely accepted as the principal (or sole) role of the frontal operculum. Clinical observations of speech apraxia have been confirmed by brain-imaging studies of speech production. We present evidence that the frontal operculum also programs limb movements. We argue that this area is a ventral counterpart of the dorsal premotor area. The two are functionally distinguished by specialization for somatic and visual space, respectively.

Emotion is critical in Mealey's conceptual arguments. However, several of her assertions about the role of emotion in sociopathy are problematic. Questions are raised regarding the link between lack of anxiety and low levels of secondary emotions such as love and sympathy, the argument that sociopaths are low in anxiety but high in neuroticism, and the designation of anxiety as a secondary emotion.

Rachlin's view of self-control as a sequence or chain of behaviors is contrasted with traditional behavioral analyses of self-control which emphasize a simplistic interpretation of the hyperbolic function relating small-sooner (SS) and larger-later (LL) reinforcers to specific behaviors. The validity of Rachlin's teleological analysis is examined in relation to the acquisition and steady-state performance of self-control behaviors. Central to an analysis of self-control is the functional difference between behavior under the control of SS and LL reinforcers, because SS-reinforced behavior is more complex due to temporal parameters.

The lambda model provides a physiologically grounded terminology for describing muscle function and emphasizes the important influence of environmental and reflex-mediated effects on final states. However, lambda itself is only a convenient point on the length-tension curve; its importance should not be overemphasized. Ascribing movement to changes in a lambda-based frame of reference is generally valid, but it leaves unanswered a number of questions concerning mechanisms.

This commentary extends arousal theory to suggest an explanation for the well-established inverse correlation between church attendance and involvement in crime. In addition, the results of two surveys of social scientists are reviewed to reveal just how little impact the biosocial/sociobiological perspective has had thus far on “mainstream” social science.

The present intractability of “self” and near intractability of “decision” make self-control a difficult topic.

Posner & Raichle's book presents methods and data that increase support for mind-brain unity and provide a method for studying and verifying brain dysfunction objectively. Their incorporation into the assessment technology of neuropsychology should accordingly constitute a major advance. In addition, these techniques may help clarify longstanding controversies in cognitive psychology such as whether perception is multimodal or amodal.