A comprehensive evidentiary regime that would encompass adaptations, exaptations, spandrels, and constraints requires both a standard to be satisfied and a predesignated default presumption to be maintained before the standard is satisfied. Andrews et al. focus principally on the former component. Some thoughts are here offered on the latter.

It is proposed that symmetry of stone tools may derive from perceptual similarity rather than from cognitively more complex awareness of symmetry. Although encodement of shapes necessarily involves symmetry (as evidenced by the confusability of enantiomorphs), it does not imply awareness of symmetry. Responses of relatively simple organisms, such as bees, support the notion that the processes involved are likely to be perceptual.

Neither evolutionary theory nor behavioral evidence is consistent with Rachlin's view of altruism as a learned, domain-general learned habit displayed because of its intrinsic value. But human beings can be psychologically motivated by altruism while still reaping a genetic benefit from their altruistic actions.

The concepts of invariants and cues are useful, as are those of dorsal and ventral streams, but Norman overgeneralizes when interweaving them. Cues are not confined to identification tasks, invariants not to action, and both can be learned.

I agree with Thomas & Karmiloff-Smith (T&K-S) in their critique of Residual Normality. However, first-person data must be integrated into their account of neurobiological development of disabilities. Furthermore, psychological development itself is not only about an individual’ brain and how it interacts with the world; rather, development depends crucially on the sociocultural context in which (normal and abnormal) children develop.

Shanker & King (S&K) provide a criticism of information-theoretic approaches to language, but the real obstacle to their dynamicist approach is the argument that representations are an indispensable part of any cognitive theory. Since the dynamicist approach has a prima facie anti-representationalist bent, the authors must show why dynamicist views can provide adequate explanations of intelligent behavior.

The dance metaphor of ape-human communication is valuable and needs to be pressed to its logical conclusion. When couples dance, they are both choreographers and dancers, and the dance arises dialectically out of the “peractions” of the dancers. We suppose that the way in which scientists communicate with their apes emerges by an analogous process.

Evidence from various subtypes of Specific Language Impairment and developmental peripheral dyslexias is presented to support the idea that even developmental disorders can be modular. However, in developmental letter position dyslexia and neglect dyslexia we show that additional errors can occur because of insufficient orthographic-lexical knowledge.

Rachlin uses the word “choice” 80 times, whereas “emotion” does not appear. In contrast, “Empathy: Its ultimate and proximate bases” by Preston and de Waal, uses the word “emotion” 139 times and “choice” once. This commentary compares these ways of approaching empathy and altruism, relating Rachlin's approach to Gilligan's Morality of Justice and Preston and de Waal's to the Morality of Caring.

Norman tries to link the ecological and constructivist approaches to the dorsal and ventral pathways of the visual system. Such a link implies that the distinction is not only one of approach, but that different issues are studied. Norman identifies these issues as perception and action. The influence of contextual illusions is critical for Norman's arguments. We point out that fast (dorsal) actions can be fooled by contextual illusions while (ventral) perceptual judgements can be insensitive to them. We conclude that both approaches can, in principle, be used to study visual information processing in both pathways.

Wynn's claims are, in principle, entirely reasonable; although, as always, the devil is in the details. With respect to Wynn's discussion of the cultural evolution of artifactual symmetry, we provide a few more arguments for the utility of mirror symmetry and extend the enquiry into the tacit and explicit processing of natural and artifactual symmetry.

Specifying exact selection pressures for identifying adaptations is unnecessary. Novel behaviors are not spandrels since they can only develop because of prior functions. An adaptationist approach has a high prior probability, whereas spandrel hypotheses attempt to prove a negative. The concept of maladaptive spandrel is criticized. The utility of dysfunctional states for identification of adaptations gone wrong is emphasized.

There are three concerns regarding Rachlin's altruism model. First, proximal causal mechanisms such as those identified by cognitive neuroscientists and behavioral neuropharmacologists are not emphasized. Second, there is a lack of clear testable hypotheses. And third, extreme forms of altruism are emphasized rather than common forms. We focus on an overarching theme – proximal mechanisms of individual differences in altruism.

Andrews et al. attempt to clarify the standards for determining whether traits are adaptations. The authors argue that tests of adaptationist hypotheses best proceed by assessing the consistency of the traits with the proposed standards. Critical tests of such standards must assess inconsistency – hypotheses must be falsifiable. To fully understand trait evolution, we must consider both adaptive and nonadaptive hypotheses.

Either genetically specified modular cognitive architecture for syntactic processing does not exist (neuroconstructivism), or there is a module but its development is so abnormal in Williams syndrome (WS) that no conclusion can be drawn about its normal architecture (moderate nativism). Radical nativism, which holds that WS is a case of intact syntax, is untenable. Specific Language Impairment and WS create a dilemma that radical nativism cannot accommodate.

Cognition is readily seen to be connected to evolution through plots of the ratio of cranial capacity to body size of hominids which show two regions of sharply increasing ratios beginning at 2.5 and 0.5 million years ago – precisely the critical times inferred by the author from his study of tools. A similar correlation exists between current human brain growth spurts and the onsets of the Piagetian stages of reasoning development. The first goal of the author's target article is stated to be “to make a case for the relevance of archeological contributions to studies of the evolution of cognition” (sect. 1, Introduction). His analysis focuses on spatial cognition.

The main function of vision in many animals is to control movement. In rodents, some visuomotor acts require the construction of models of the external world while others rely on Gibsonian invariants. Such findings support Norman's dual processing approach but it is not clear that the two types of processing rely on homologs of visual processing streams described in primates.

The highly recommended transposition of the dynamic system approach for tackling the question of apes' linguistic abilities has clearly not led to a demonstration that these primates have acquired language. Fundamental differences related to functional modalities – namely, use of the declarative and the form of engagement between mother and infant – can be observed in the way humans and apes use their communicatory systems.

Several lines of evidence indicate that rapid target-aiming movements, involving both the eyes and hand, can be biased by the visual context in which the movements are performed. Some of these contextual influences carry-over from trial to trial. This research indicates that dissociation between the dorsal and ventral systems based on speed, conscious awareness, and frame of reference is far from clear.

The authors outline research strategies that may identify the possible adaptive value of a trait. But this does not solve the problem of how to decide which characteristics of living organisms require an adaptive explanation. I suggest that knowledge of the ontogenetic and phylogenetic construction of a trait facilitates the identification of features that may have been acted on by natural selection.