The authors contributed equally to this paper. Order of authorship was determined alphabetically. Correspondence may be addressed to any of the authors.Adaptationism is a research strategy that seeks to identify adaptations and the specific selective forces that drove their evolution in past environments. Since the mid-1970s, paleontologist Stephen J. Gould and geneticist Richard Lewontin have been critical of adaptationism, especially as applied toward understanding human behavior and cognition. Perhaps the most prominent criticism they made was that adaptationist explanations were analogous to Rudyard Kipling's Just So Stories (outlandish explanations for questions such as how the elephant got its trunk). Since storytelling (through the generation of hypotheses and the making of inferences) is an inherent part of science, the criticism refers to the acceptance of stories without sufficient empirical evidence. In particular, Gould, Lewontin, and their colleagues argue that adaptationists often use inappropriate evidentiary standards for identifying adaptations and their functions, and that they often fail to consider alternative hypotheses to adaptation. Playing prominently in both of these criticisms are the concepts of constraint, spandrel, and exaptation. In this article we discuss the standards of evidence that could be used to identify adaptations and when and how they may be appropriately used. Moreover, building an empirical case that certain features of a trait are best explained by exaptation, spandrel, or constraint requires demonstrating that the trait's features cannot be better accounted for by adaptationist hypotheses. Thus, we argue that the testing of alternatives requires the consideration, testing, and systematic rejection of adaptationist hypotheses. Where possible, we illustrate our points with examples taken from human behavior and cognition.

Self-awareness is thought to be tied to processes of higher-order perspective taking including empathy. These abilities appear to be reserved for humans, great apes, and possibly, dolphins. Recent examinations reveal that both self-awareness and empathy may have origins in the right hemisphere. It is possible that, as in language, lateralization plays a key role in the development of higher-order perspective taking and self-awareness.

Carruthers presents evidence concerning the cross-modular integration of information in human subjects which appears to support the “cognitive conception of language.” According to this conception, language is not just a means of communication, but also a representational medium of thought. However, Carruthers overlooks the possibility that language, in both its communicative and cognitive roles, is a nonrepresentational system of conventional signals – that words are not a medium we think in, but a tool we think with. The evidence he cites is equivocal when it comes to choosing between the cognitive conception and this radical communicative conception of language.

I argue that Perruchet & Vinter's claim that representations are conscious, and processes unconscious, gives too much ground to the cognitive unconscious; and that the boundary between conscious and unconscious mental phenomena is unlikely to fall neatly along these lines. I also propose that in the absence of more detailed models that demonstrably provide a reasonable account of the data, claims that associative mechanisms may underlie all cognition are premature.

With admirable clarity, Pylyshyn shows that there is little evidence that mental imagery is strongly constrained to be analog. He urges that imagery must be considered part of a more general symbolic system. The ultimate solution to the challenges of image theory, however, rest on understanding the manner in which mental imagery is both a symbolic and an analog system.

Carruthers clearly identifies the basic issues involved in language and thought relations and argues for an adaptive central model. Similar conclusions were reached by classical research in the inner speech tradition. Sokolov (1968; 1972) especially emphasized that inner speech appears only when the task is difficult. The use of inner speech is not a necessity to transform representations, but it is called for when transformations become difficult. This might be related to the cognitive reorganizations leading to language as emphasized by Donald (2001).

We address the issue of the nature of representations during development regarding language acquisition. The controversy of syntax as a process or operation for representation formation and syntax as a representation in itself is discussed. Eliminating the cognitive unconscious does not warrant a simplified, more parsimonious approach to human cognition in general.

Strong adaptationists would explain complex organic designs as specific adaptations to particular ancestral environments. Weak adaptationists don't assume that complex organic functioning represents evolutionary design in the sense of niche-specific adaptation. For some domain-specific competencies (folkbiology) strong adaptationism is useful, not necessary. With group-level belief systems (religion), strong adaptationism can become spurious pseudo-adaptationism. In other cases (language), weak adaptationism proves productive.

Shanker & King (S&K) fail to provide substantive reasons for a paradigm shift in the study of communication because nonstandard and equivocal use of terminology obscures and undercuts their arguments.

Two major problems exist in studying development: Similar behaviors do not need to reflect the same underlying process, different behaviors can reflect the same process; earlier behaviors do not necessarily lead to later behaviors. Empathy, rather than social contagion, is supported by different processes; contagion supported by prewired species behavior, empathy by cognitions, in particular, the cognitions about the self – a meta-representation.

Imagery has played an important, albeit controversial, role in the study of memory psychophysics. In this commentary we critically examine the available data bearing on whether pictorial based depictions of remembered perceptual events are activated and scanned in each of a number of different psychophysical tasks.

The Perception-Action Model of empathy (PAM) is both sufficiently broad and sufficiently detailed to be able to describe and accommodate a wide range of phenomena – including the apparent “cold-heartedness” or lack of empathy of psychopaths. We show how the physiological, cognitive, and emotional elements of the PAM map onto known and hypothesized attributes of the psychopathic personality.

Carruthers argues that natural language is the medium of non-domain-specific thought in humans. The general idea is that a certain type of thinking is conducted in natural language. It’ not exactly clear, however, what type of thinking this is. I suggest two different ways of interpreting Carruthers’ thesis on this point and argue that neither of them squares well with central-process modularism.

There are striking similarities between Perruchet & Vinter's SOC theory and the theories that they claim to be in opposition to. First, both kinds of theory lead to the induction of knowledge of complex patterns in the environment that serve the function of rules. Second, both involve unconscious mental processes of induction resulting in at least some conscious knowledge.

Shanker & King's (S&K's) dynamic systems approach converges with developments in social anthropological studies of communication which were long ago anticipated in the writings of Volosinov and Schutz. Following a review of these writings, this commentary suggests that a dynamic systems approach should distinguish communion from communication. It concludes with a remark on the evolutionary implications of the approach.

In addition to ensuring that appropriate standards of evidence are employed when attempting to identify adaptations, researchers should investigate all nonevolutionary factors that could potentially explain their results. Evolutionary analyses may be undermined by alternative, non-evolutionary explanations either because not all relevant information is included in an evolutionary analysis, or because inappropriate methods incapable of detecting an adaptation are employed.

Mammalian brains contain a variety of self-centered socio-emotional systems. An understanding of how they interact with more recent cognitive structures may be essential for understanding empathy. Preston & de Waal have neglected this vast territory of proximal brain issues in their analysis.

A central claim of the target article is that language is the medium of domain-general, cross-modular thought; and according to Carruthers, the main, direct evidence for this thesis comes from a series of fascinating studies on spatial reorientation. I argue that the these studies, in fact, provide us with no reason whatsoever to accept this cognitive conception of language.

Shanker & King (S&K) rightly stress that recent ape language research has important implications for language development and origins. But the evidence does not warrant their conclusion that we can dispense with representations. Indeed, their own discussion of the nature of communication highlights the central role that representations must play in our models of communicative competence, in and out of language.

One important difference between adaptive and nonadaptive explanations can be found in the evolutionary sequence of structural and functional modifications. Phylogenetic analysis (cladistics) provides a powerful methodology for distinguishing exaptation from adaptation, by indicating whether character traits have predated, accompanied, or followed evolution of particular functions. Such analysis yields falsifiable hypotheses that can help to distinguish causal relationships from mere correlation.