Plamondon's kinematic theory is very powerful from a descriptive point of view. Unfortunately, the fact that it neglects some fundamental features of the motor system, such as nonlinear inertial torque interactions or joint redundancies, limits its explanatory power and biological validity. As a consequence, the data presented by Plamondon & Alimi should be analyzed and interpreted with caution. There appears to be a gap between the observations reported by the authors and some of the conclusions they draw.

Jeannerod's target article and a number of commentators stressed the necessity of distinguishing between motor representation and perceptual images. A patient with a lesion of the central somatosensory pathways allowed us to test for this distinction. The outcome suggests that motor images may not be visual and that the “pragmatic” framework proposed by Jeannerod for vision can apply to other sensory modalities.

The concept of a conservative control strategy minimizing the number of degrees of freedom used is criticised with reference to 3-D simple reaching and grasping experiments. The vector error in a redundant system would not be the prime controlled variable, but rather the posture for reaching, as exemplified by nearly straight displacements in joint space as opposed to curved ones in task space.

A visual analogue, two-route model of somatosensory processing is advanced in this commentary. Touch for perception is seen as separate from, although interconnected with, touch for action. Separate modules are additionally proposed for internal (body) and external (object-related) somatosensation. Here we ask whether dissociation (divide) guarantees better efficiency (impera) in terms of the heuristic model within the somatosensory modality and across modalities.

Some data concerning visual illusions are hardly compatible with the perception–action model, assuming that only the perception system is influenced by visual context. The planning–control dichotomy offers an alternative that better accounts for some controversy in experimental data. We tested the two models by submitting the patient I. G. to the induced Roelofs effect. The similitude of the results of I. G. and control subjects favoured Glover's model, which, however, presents a paradox that needs to be clarified.

Is there any ecological purpose in assuming that perception for action exists only through a global array of energy? Unlike Stoffregen & Bardy, who assume that behavior consists of movements, we would argue that behavior consists of a stable coupling between perception and action achieved through experience in an adaptive context. Determining target position in an aiming manual task and temporal control of impact movement illustrate that patterns of energy used for action are task-dependent.

Dienes & Perner's (D&P's) target articles proposes an analysis of explicit knowledge based on a progressive transformation of implicit into explicit products, applying this gradient to different aspects of knowledge that can be represented. The goal is to integrate a philosophical concept of knowledge with relevant psychophysical and neuropsychological data. D&P seem to fill an impressive portion of the gap between these two areas. We focus on two examples where a full synthesis of theoretical and empirical data seems difficult to establish and would require further refinement of the model: action representation and the closely related consciousness of action, which is in turn related to self-consciousness.

A further step in Pylyshyn's discontinuity thesis is to examine the penetrability of haptic (tactual-kinesthetic) perception. The study of the perception of orientation and the “oblique effect” (lower performance in oblique orientations than in vertical–horizontal orientations) in the visual and haptic modalities allows this question to be discussed. We suggest that part of the visual process generating the visual oblique effect is cognitively impenetrable, whereas all haptic processes generating the haptic oblique effect are cognitively penetrable.

The originality of Glenberg's theoretical account lies in the claim that memory works in the service of physical interaction with the three-dimensional world. Little consideration is given, however, to the role of memory in action. We present and discuss data on spatial memory for action. These empirical data constitute the first step of reasoning about the link between memory and action, and allow several aspects of Glenberg's theory to be tested.