It appears that knappers intentionally produced symmetrical stones. Use of the dorsal pathways in knapping does not preclude shape perception, nor does it obviate use of ventral pathways in other tasks in Homo sapiens 400,000 years ago. Shape perception precedes production in present-day human infants, suggesting that symmetry perception was used by knappers of symmetrical stones.

We support Shanker & King's (S&K's) proposal for a dynamic systems approach in ape language research, but question their vision of what it means to have language. Language plays an essential role in the making of the human mind. It underlies any kind of human interaction and codetermines perception and action. Moreover, what gives human thought the very characteristic architecture of textuality criterially requires a third party.

Using a simple learning agent, we show that learning self-control in the primrose path experiment does parallel learning cooperation in the prisoner's dilemma. But Rachlin's claim that “there is no essential difference between self-control and altruism” is too strong. Only iterated prisoner's dilemmas played against reciprocators are reduced to self-control problems. There is more to cooperation than self-control and even altruism in a strong sense.

Thomas & Karmiloff-Smith (T&K-S) raise the excellent and, in retrospect, obvious point that in a dynamic learning environment where feedback is possible, we should expect networks to adapt to damage by altering details of their behavior. We should therefore not expect that developmental disorders should result in “normal” modules. The implications of this point go much further, since interprocess dependency in the brain does not rely only on learned neural connections. This argues strongly against behavioral and process-related definitions, as opposed to structural and architecture-related definitions, of mental modularity.

I make two claims about cognitive archaeology. I question its role, seeing psychology as yet another contributor to the archaeological tool-kit rather than as something unique. I then suggest that cognitive archaeology is not in a position to provide evolutionary contexts without other disciplines. As a consequence it cannot deliver on the provision of evolutionary contexts for cognitive evolution.

Constructivist and ecological approaches are also observed in tactile perception studies. The question is whether identification and localization are dissociated in the tactile modality as well, and whether Norman's conception may be generalized to the field of touch. An analogue to blindsight was evidenced in passive touch, but no such dissociation was observed in active touch. A study is in progress in this domain.

We agree with Rachlin's argument that altruism is best understood as a case of self-control, and that a behavioral analysis is appropriate. However, the appeal to teleological behaviorism and the value of behavioral patterns may be unnecessary. Instead, we argue that altruism can generally be explained with traditional behavioral principles such as negative reinforcement, conditioned reinforcement, and rule-governed behavior.

Andrews et al. present a clear discussion of the various criteria needed to identify adaptations. However, they also imply a history of the debate between adaptationists and their critics that is incomplete. The history implied is one of only genuine scientific disagreement. This neglects the role of nonscientific motives and strawman arguments on behalf of the critics of adaptationists.

Models of the architecture of mature cognitive systems can inform the study of normal and disordered cognitive development, if one distinguishes between proximal and distal causes of performance. The assumption of residual normality need not be made in order to apply adult models to performance early in development, because these models can be modified to reflect the results of compensatory processing.

This commentary discusses the dynamic systems (DS) approach to communication over an information-processing (IP) model. The commenters suggest that the authors of the target article, in their treatment of the issue, do not identify the central failing of the IP model. Further, it is suggested that the DS approach should include examination of mechanisms in the emergence of symbolic communication.

The ability to recognise the actions of conspecifics from displays of biological motion is an essential perceptual capacity. Physiological and psychological evidence suggest that the visual processing of biological motion involves close interaction between the dorsal and ventral systems. Norman's strong emphasis on the functional differences between these systems may impede understanding of their interactions.

Whatever else language may be, it is complex and multifaceted. Shanker & King (S&K) have tried to contrast a dynamic interactive view of language with an information processing view. I take issue with two main claims: first, that the dynamic interactive view of language is a “new paradigm” in either animal research or human language studies; and second, that the dynamic systems language-as-dance view of language is in any way incompatible with an information-processing view of language. That some information is defined in coregulated social interaction guarantees the dancing. That all information is composed of relevant differences guarantees the information processing.

Homology can provide strong evidence against exapted learning mechanism (ELM) explanations for psychological and behavioral traits. Homologous traits are constructed by commonly inherited developmental mechanisms. As such, demonstration of homology for a trait argues for its construction by an inherited rather than an exapted developmental process. We conclude that comparative evidence can play an important evidentiary role within evolutionary psychology.

Cognitive psychologists tend to treat intentionality as a control variable during experiments, yet ignore it when generating mechanistic descriptions of performance. Wynn's work brings this conflict into striking relief and, when considered in relation to recent neurophysiological findings, makes it clear that intentionality can be regarded mechanistically if one defines it as the planning of distal effects.

If altruism requires self-control, people must consider altruistic acts as costly, the benefits of which will only be recouped in the future. By contrast, I shall present evidence that altruism is dictated by emotions: Altruists secure an immediate payoff from performing altruistic acts, so no element of self-control is present, and no future reward is required or expected.

Thomas & Karmiloff-Smith (T&K-S) show that the assumption of residual normality (RN) does not hold in connectionist simulations, and argue that RN has been inappropriately applied to childhood disorders. We agree. However, we suggest that the RN hypothesis may never have been fully viable, either empirically or computationally.

This commentary questions the authors’claim that cognitive neuropsychology is defined by modularity and that other theoretical frames, that is, connectionism, are a priori rejected. It also points to the fact that whereas in genetic disorders there are developmental delay and asynchrony, there are few reports of deviant developmental trajectories that are never seen in typical development. It is suggested that the possibility that structure does not equal function in the developing brain, may be a viable option.

The primrose path and prisoner's dilemma paradigms may require cognitive (executive) control: The active maintenance of context representations in lateral prefrontal cortex to provide top-down support for specific behaviors in the face of short delays or stronger response tendencies. This perspective suggests further tests of whether altruism is a type of self-control, including brain imaging, induced affect, and dual-task studies.

Wynn describes a revolution in cognitive abilities some 500,000 years ago, which added new sophistication to the curiosity of early man – the ability to form hypotheses. This derivative of archaic curiosity is a fundamental feature of learning, and it is our contention that the naive hypothesis testing behavior of early man will have left a distinctive trail in the archaeological record.

Norman's assigning of the constructivist percept-percept coupling approach and the ecological affordances approach to the ventral and dorsal visual systems, respectively, makes a more workable metatheory than each taken separately, but brings both under closer inspection.