In the behavioral literature on human movement, a distinction is made between the learning of parameters and the learning of new movement forms or topologies. Whereas the target articles by Thach, Smith, and Houk et al. provide evidence for cerebellar involvement in parametrization learning and adaptation, the evidence in favor of its involvement in the generation of new movement patterns is less straightforward. A case is made for focusing more attention on the latter issue in the future. This would directly help to bridge the gap between current neurophysiological approaches to the role of the cerebellum and the behavioral expressions of human motor learning, [HOUK et al.; SMITH; THACH]

Geary's model is a worthy effort, but ambiguous on important issues. It ignores differential resource allocation, although this follows directly from sexual selection via differential parental investment. Dimorphism in primary traits is arbitrarily attributed to sexual selection via intramale competition, rather than direct evolutionary pressures. Dubious predictions are made about the consequences of raising mathematics achievement.

Neurobiological models of language need a level of analysis that can account for the typical range of language phenomena. Because linguistically motivated models have been successful in explaining numerous language properties, it is premature to dismiss them as biologically irrelevant. Models attempting to unify neurobiology and linguistics need to be sensitive to both sources of evidence.

The guideline for therapy should be the improvement of the individual's functionality, not the acquisition of the ill-defined “goldstandard” of normal movement. However, Latash & Anson's suggestion that only primary causes of dysfunction should be treated is problematic for two reasons: First, the distinction between genuine and adaptive changes in motor performance is not always possible, and second, adaptive changes do not necessarily improve motor function, but may actually be detrimental to the system's performance.

Müller's target article aims to summarize approaches to the question of how language elements (phonemes, morphemes, etc.) and rules are laid down in the brain. However, it suffers from being too vague about basic assumptions and empirical predictions of neurobiological models, and the empirical evidence available to test the models is not appropriately evaluated. (1) In a neuroscientific model of language, different cortical localizations of words can only be based on biological principles. These need to be made explicit. (2) Evidence for and against word class differences could be evaluated more rigorously. (3) All (and only) humans are able to learn languages with complex syntactic structures; it is, therefore, not appropriate to deny innateness and universality of syntactic principles. The real question appears to be the following: Which neurobiological principles are the linguistic principles based on?

The motor deficits observed in patients following some lesions of the central nervous system may be viewed as falling at one extreme of the continuum of possible motor behaviours. They are usually associated with an impaired ability to select and control specific movements from the available repertoire. Such movements may not be viewed as abnormal. However, it is unlikely that the primary motor deficits can all be considered adaptive.

For reasons I have never understood, some students of the cerebellum have been unwilling to accept the now overwhelming evidence that the cerebellum exhibits lasting synaptic plasticity and plays an essential role in some forms of learning and memory. With a few exceptions (e.g., target article by SIMPSON et al.) this is no longer the case, as is clear in the excellent target articles on cerebellar LTD and the excellent target review by HOUK et al. [CRÉPEL et al.; HOUR et al.; KANO; LINDEN; SIMPSON et al.; SMITH; VINCENT]

We evaluate three of Geary's claims, finding that (1) there is little evidence for sex differences in object- vs. person-orientation; (2) sex differences in competition, even if biologically caused, lead to sex differences in mathematics only given a certain style of teaching; and (3) sex differences in mental rotation, though real, are not well explained in a sociobiological framework or by the proximate biological variables assumed by Geary.

We agree with Müller's epigenetic view of evolution and ontogeny and applaud his multilevel perspective. With him, we stress the importance in ontogeny of progressive specialisation rather than prewired structures. However, we argue that he slips from “speech” to “language” and that, in seeking homologies, these two levels need to be kept separate in the analysis of evolution and ontogeny.

Geary's is the traditional view of the sexes. Yet each part of his argument – the move from sex differences in spatial ability and social preferences to a sex difference in mathematical ability, the claim that the former are biologically primary, and the sociobiological explanation of these differences – requires considerable further work. The notion of a biologically secondary ability is itself problematic.

PET studies using classical conditioning paradigms are reported. It is emphasized that PET studies show “cerebellar involvement” and not “specific function” in learning paradigms. The importance of dissociating motor performance and learning deficits in human lesions studies is demonstrated in two exemplary studies. The different role of the cerebellum in adaptation of postural reflexes and learning of complex voluntary arm movements is discussed, [THACH]

Spatial and mathematical abilities may be “sex-limited” traits. A sex-limited trait has the same determinants of variation within the sexes, but the genetic or environmental effects would be differentially expressed in males and females. New advances in structural equation modeling allow means and variation to be estimated simultaneously. When these statistical methods are combined with a genetically informative research design, it should be possible to demonstrate that the genes influencing spatial and mathematical abilities are sex-limited in their expression. This approach would give an empirical confirmation of Geary's evolutionary speculations.

Thach, following the Marr-Albus theory, suggests that the cerebellum contributes to sensorimotor learning through a process of context-response linkage. However, perceptual learning studies demonstrate that the context itself is subject to adaptive modifications and recent evidence has shown that motor responses derived from such perceptions display appropriate changes which may be quite independent of cerebellar processing. [HOUR et al.; SMITH; THACH]

It is the contention of Latash & Anson (L&A) that in atypical populations, such as those with cognitive, central neurological, or peripheral disorders, the central nervous system (CNS) is capable of producing more effective, though often less “normal,” movement patterns ifleft to its own devices. It is the aim of this commentary to extend their argument to other populations by pointing out the many parallels with development of movement patterns in sport.

The belief that syntax is an innate, autonomous, species-specific module is highly questionable. Syntax demonstrates the mosaic nature of evolutionary change, in that it made use of (and led to the enhancement of) numerous preexisting neurocognitive features. It is best understood as an emergent characteristic of the explosion of semantic complexity that occurred during hominid evolution.

Müller's review of the neuroscientific evidence undermines nativist claims for autonomous syntax and the argument from the poverty of the stimulus. Generativists will appeal to data from language acquisition, but here too there is growing evidence against the nativist position. Epigenetic naturalism, the developmental alternative to nativism, can be extended to epigenetic socionaturalism, acknowledging the importance of sociocultural processes in language and cognitive development.

The suggestion that movement disorders exhibited by people with central nervous system (CNS) dysfunction should be considered normal and therefore not rehabilitated is rejected from three standpoints: (1) the CNS does not always select the best movement patterns for optimal long term outcome, (2) there is literature demonstrating that rehabilitation enhances motor function and independence, and (3) there exists a capacity for motor recovery and motor skill learning following brain damage.

Spatial visualization as a key variable in sex-related differences in mathematical problem solving and spatial aspects of geometry is traced to the 1960s. More recent relevant data are presented. The variability debate is traced to the latter part of the nineteenth century and an explanation for it is suggested. An idea is presented for further research to clarify sex-related brain laterality differences in solving spatial problems.

It is argued that stiffness is, as Smith assumes, a likely movement-control parameter for the brain, as is supported by the results of several behavioral experiments. However, without further elaboration of what specific type and implementation of stiffness is meant it is perhaps premature to speculate on its possible locus of control, [SMITH]