Perhaps in addition to language being a potential medium of domain-general thought, as suggested by Carruthers, language may also play another role in conceptual development: Words are “essence placeholders.” Evidence is presented from studies on categorization, object individuation, and inductive inference in infancy. The assumption that words are essence placeholders may be a mechanism by which infants acquire kind concepts.

The authors reject a computationally powerful unconscious. Instead, they suggest that simple unconscious processes give rise to complex conscious representations. We discuss evidence showing contrastive effects of conscious and unconscious processes, suggesting a distinction between these types of processes. In our view, conscious processes often serve to correct or control negative consequences of relatively simple unconscious processes.

The aptationist program includes attempts at sorting adaptations from exaptations, and therefore requires knowledge of historical changes in biological character states (traits) and their effects or functions, particularly for nonoptimal aptations. Phylogenetic inference is a key approach for historical aspects of evolutionary hypotheses, particularly testing evolutionary scenarios, and such “tree-thinking” investigation is directly relevant to the aptationist program.

Although we applaud the interactivist approach to language and communication taken in the target article, we notice that Shanker & King (S&K) give little attention to the theoretical frameworks developed by dynamical system theorists. We point out how the dynamical idea of causality, viewed as multidirectional across multiple scales of organization, could further strengthen the position taken in the target article.

What is difficult to imagine is also surprising to perceive. This indicates that active visual imagery is an integral part of active visual perception. Erroneous mental transformations provide clues to prior assumptions in visual imagery, just as visual illusions provide clues to perceptual assumptions. Visual imagery and perception share generic assumptions about invariants in images of rigid objects.

Andrews et al. present a form of instrumental adaptationism that is designed to test the hypothesis that a given trait is an adaptation. This epistemological commitment aims to make clear statements about behavioural natural kinds. The instrumental logic is sound, but it is the limits of our empirical imagination that can cause problems for theory construction.

Through the concept of self-organizing consciousness (SOC), we posit that the dynamic of the mind stems from the recurrent interplay between the properties of conscious experiences and the properties of the world, hence making it unnecessary to postulate the existence of an unconscious mental level. In contrast, arguments are provided by commentators for the need for a functional level of organization located between the neural and the conscious. Other commentaries challenge us concerning the ability of our model to account for specific phenomena in the domains of language, reasoning, incubation, and creativity. The possibility of unconscious semantic access and other alleged instances of adapted performance in the absence of any conscious counterpart are also put forth as evidence against our view. Our response emphasizes the fact that opponents to our model often present as factual, theory-free evidence which is in fact nothing more than the postulates underlying the classical computational framework.

Viewing communication as a dynamic system is laudable; arguing that the approach is novel is questionable. Some researchers studying nonhuman communication other than ape language have been using such an approach for decades. A brief description of an avian system provides one such example. Interestingly, the dynamic social system described in the target article may have a developmental neuronal basis.

The author argues that the theory of a dorsal/ventral stream for visual processing can be used to reconcile the constructivist and direct perception theories. My commentary discusses neurophysiological and psychophysical studies that run counter to the view. In addition, the central issue of debate between the constructionist and direct perception approaches regarding what is visual information is discussed.

The present response elucidates, elaborates, and defends the main thesis advanced in the target article: namely, that natural-language sentences play a constitutive role in some human thought processes, and that they are responsible for some of the distinctive flexibility of human thinking, serving to integrate the outputs of a variety of conceptual modules. Section R1 clarifies and elaborates this main thesis, responding to a number of objections and misunderstandings. Section R2 considers three contrasting accounts of the mechanism of intermodular integration. Section R3 discusses objections to some of the empirical data supporting my main thesis. Section R4 criticizes some competing theories of the role of language in cognition. And section R5 considers some proposed supplementary cognitive roles that language might play.

Although Shanker & King (S&K) disregard the behavioral paradigm, their arguments are reminiscent of those in Skinner's Verbal Behavior (1957). Like S&K, Skinner maintained that communication is not appropriately characterized as the transmission of information between individuals. In contrast to the paradigm advocated by S&K, however, the behavioral paradigm emphasizes prediction and control as important scientific goals.

It is often assumed that similar domain-specific behavioural impairments found in cases of adult brain damage and developmental disorders correspond to similar underlying causes, and can serve as convergent evidence for the modular structure of the normal adult cognitive system. We argue that this correspondence is contingent on an unsupported assumption that atypical development can produce selective deficits while the rest of the system develops normally (Residual Normality), and that this assumption tends to bias data collection in the field. Based on a review of connectionist models of acquired and developmental disorders in the domains of reading and past tense, as well as on new simulations, we explore the computational viability of Residual Normality and the potential role of development in producing behavioural deficits. Simulations demonstrate that damage to a developmental model can produce very different effects depending on whether it occurs prior to or following the training process. Because developmental disorders typically involve damage prior to learning, we conclude that the developmental process is a key component of the explanation of endstate impairments in such disorders. Further simulations demonstrate that in simple connectionist learning systems, the assumption of Residual Normality is undermined by processes of compensation or alteration elsewhere in the system. We outline the precise computational conditions required for Residual Normality to hold in development, and suggest that in many cases it is an unlikely hypothesis. We conclude that in developmental disorders, inferences from behavioural deficits to underlying structure crucially depend on developmental conditions, and that the process of ontogenetic development cannot be ignored in constructing models of developmental disorders.

Andrews et al. claim that Gould and Lewontin's critique of adaptationism is largely epistemological rather than ontological. In this commentary I argue that, on the contrary, the deepest part of their critique is ontological, raising concerns about the existence of the traits that are the subjects of adaptationist theorising. Andrews et al.'s failure to address this problem undermines their defence of adaptationism.

After thirty years of the current “imagery debate,” it appears far from resolved, even though there seems to be a growing acceptance that a cortical display cannot be identified directly with the experienced mental image, nor can it account for the experimental findings on imagery, at least not without additional ad hoc assumptions. The commentaries on the target article range from the annoyed to the supportive, with a surprising number of the latter. In this response I attempt to correct some misreadings of the target article and discuss some of the ideas and evidence introduced by the commentators – much of which I found helpful, even though they do not alter my basic thesis. I also further develop the idea that the spatial character of images may come from the way they are connected to our immediate or immediately-recalled environment (by attention or by visual indexes) and towards which we may orient while we are imaging, thus leaving the alleged spatial properties of images outside the head and freeing image-representations from having to be displayed on any surface.

Our commentary focuses on the functional link between the ventral and dorsal systems implied by Norman, as they relate to overt movement. While issues relating to space perception and size constancy are the primary justification for this dual-process theory, the philosophical extensions of this approach are less consistent with examination of motor control and, in particular, motor learning.

Archaeology can provide two bodies of information relevant to the understanding of the evolution of human cognition – the timing of developments, and the evolutionary context of these developments. The challenge is methodological. Archaeology must document attributes that have direct implications for underlying cognitive mechanisms. One example of such a cognitive archaeology is found in spatial cognition. The archaeological record documents an evolutionary sequence that begins with ape-equivalent spatial abilities 2.5 million years ago and ends with the appearance of modern abilities in the still remote past of 400,000 years ago. The timing of these developments reveals two major episodes in the evolution in spatial ability, one, 1.5 million years ago and the other, one million years later. The two episodes of development in spatial cognition had very different evolutionary contexts. The first was associated with the shift to an open country adaptive niche that occurred early in the time range of Homo erectus. The second was associated with no clear adaptive shift, though it does appear to have coincided with the invasion of more hostile environments and the appearance of systematic hunting of large mammals. Neither, however, occurred in a context of modern hunting and gathering.

It is anthropomorphic to speak of Nature designing adaptations for a specific function, as if with conscious intent. Any effect constitutes an adaptive function if it contributes to survival and to reproduction. Natural selection is blind to what might have been the original function. Mutations arise by purest accident and are selected based on whatever fortuitous effects they might produce.

Lack of symmetry of stone tools does not require that hominids making asymmetric tools are incapable of doing better. By analogy, differences between stone tools of early humans and modern technology arose without genetic change. A conservative assumption is that symmetry of stone artifacts may have arisen simply because symmetrical tools work better when used for striking and chopping rather than scraping.

Cognitive frameworks provide important means for uniting concepts of specificity, cognition, and dynamic change in development. Two points are challenged by evidence from special populations: (1) that boundary constraints such as Residual Normality and a cognitive “endstate” compromise the use of cognitive models; and (2) the developmental process itself automatically rejects either Residual Normality or residual deviance from typical development.

Shanker & King (S&K) argue that information-theoretic approaches to communication are too rigid to capture the ebb and flow of communicative interactions. They advocate instead a dynamic systems approach based on the metaphor of dance. We focus on two problems arising from the dance metaphor: first, that its inherently cooperative tone contradicts basic tenets of behavioral biology; and second, that it risks obscuring rather than clarifying the details of communicative interactions.