An evolutionary theory of schizophrenia needs to address all symptoms associated with the condition. Burns' framework could be extended in a way embracing behavioural signs such as catatonia. Burns' theory is, however, not specific to schizophrenia. Since no one single symptom exists that is pathognomonic for “schizophrenia,” an evolutionary proposal of psychiatric disorders raises the question whether our anachronistic psychiatric nosology warrants revision.

Although I am broadly in sympathy with Carpendale & Lewis's (C&L's) version of social constructivism, I raise two issues they might address. One bears on the question of how social understanding develops: Is their resistance to individualism inappropriately combined with a resistance to internalism? A second question concerns a more radical implication of their view for what social understanding is.

Carpendale & Lewis's (C&L's) constructivist account needs greater emphasis on how individual differences in caregivers' impact on the efficacy of epistemic triangle interaction in fostering children's understanding of mind. Caregivers' attunement to their infants' mental states and their willingness to enable infants to participate in exchanges about the mind are posited as important determinants of effective epistemic triangle interaction.

Grush's emulation theory comprises both modality-specific and amodal emulators. I suggest that the amodal variety be replaced by multisensory emulators. The key distinction is that multisensory processing retains the characteristics of individual sensory modalities, in contrast to amodal processing. The latter term is better reserved for conceptual and linguistic systems, rather than perception or emulation.

I agree with Burns that an evolutionary theory is required, but I question his multifactorial premise. The arguments for an evolutionary theory are stronger, and one that is more precise than that presented by Burns has already been formulated. This theory, that schizophrenia is “the price that Homo sapiens pays for language,” (Crow 1997a; 2000b, 2004c), generates testable predictions absent from Burns' presentation.

Can evolutionary models explain food sharing in traditional human societies? Gurven's analysis cannot rule out any of the models (kin selection, reciprocal altruism, tolerated scrounging, costly signaling, or by-product mutualism), and quantitative partitioning of relative importance is not feasible. For now, the hypotheses seem like the proverbial blind men examining the elephant: each was partly in the right, and all were in the wrong!

In his state-of-the-art review, Gurven compares evolutionary theories of food transfers in ethnographic settings. Although this is useful, I suggest that one must first try to determine the utility of food transfers before making predictions about which parties ought to receive food. In addition, I argue that tests of kin selection theory present a special problem in food transfers.

This commentary addresses the neural implementation of emulation, mostly using findings from functional Magnetic Resonance Imaging (fMRI). Furthermore, both empirical and theoretical suggestions are discussed that render two aspects of emulation theory redundant: independent modal emulators and extra measurement of amodal emulation. This modified emulation theory can conceptually integrate simulation theory and also get rid of some problematic philosophical implications.

There is evidence that people with schizophrenia have difficulties in some (recently evolved) competencies for processing social information. However, a case can be made that vulnerabilities can also lie in (previously evolved) threat and safeness processing systems. Evolutionary models may need to consider interactions between genetic sensitivities, early experiences of threat/safeness, and later cognitive vulnerabilities. Psychological treatments must address issues of experienced threat and safeness before working on more cognitive competencies.

We agree that social interaction is crucial for understanding the development of theory of mind, but suggest that further elaboration of certain issues is needed. Detailed description of the knowledge structure of a developing theory of mind is necessary, and the notion of criteria for the use of mental state terms requires consideration of the sentence structures in which such terms appear.

While schizophrenia may be genetically determined up to a point, neither it nor its nearest relatives offer any sort of reproductive advantage to its sufferers. Instead, from an evolutionary point of view, schizophrenia is benign – it neither promotes nor inhibits survival to reproduction. Because it is benign, its rate of occurrence should remain fairly constant over time.

In this comment, I describe how the processes of free giving can be simulated with the help of the Reflexive Intentional Model of the Subject (RIMS). This simulation demonstrates that there are two essential factors affecting the size of a share given to others: limits accepted by the society as “normal,” and the individual's subjective estimation of a mean share donated by other members of the society.

Grush's emulator model appears to be consistent with the idea of a body schema, that is, a detailed mental representation of the body, its structure, and movement in relation to the environment. If the emulator is equivalent to a body schema, then the next step will be to specify how the emulator accounts for neuropsychological and developmental phenomena that have long been hypothesized to involve the body schema.

If anything, Carpendale & Lewis's (C&L's) target article could have gone even further in challenging the view that a radical conceptual shift equips children with a theory of mind. Also, the authors should have elaborated on why their social constructivist account is more plausible than nativism. Their argument against simulation theory is perhaps the least-developed part of their thesis, and does little service to their cause.

Carpendale & Lewis (C&L) contend that correlations between sociolinguistic factors and theory-of-mind performance indicate that social knowledge develops from social interactive processes. However, theory-theory proponents also regard these correlations as compatible with their view of how mental concepts develop. A more fruitful distinction lies in the differences of both accounts in explaining how mental concepts acquire meaning.

Emphasis on cross-cultural testing, multiple currencies, multivariate analyses, and levels of explanation makes this an important paper. However, it does not distinguish current function from evolutionary origin; it lacks history. Rather than distinct alternatives, tolerated scrounging (TS), costly signaling (CS), and reciprocal altruism (RA) are likely to be sequentially evolved components of a single integrated system (and kin selection (KS) important only among very close relatives).

Multidisciplinary studies indicate that auditory hallucinations may arise from speech perception neurocircuitry without disrupted theory of mind capacities. Computer simulations of excessive pruning in speech perception neural networks provide a model for these hallucinations and demonstrate that connectivity reductions just below a “psychotogenic threshold” enhance information processing. These data suggest a process whereby vulnerability to schizophrenia is maintained in the human population despite reproductive disadvantages of this illness.

One property of the emulator framework presented by Grush is that imagery operates off-line. Contrary to this viewpoint, we present evidence showing that mental rotation of a simple figure modulates low-level features of drawing articulation. This effect is dependent upon the type of rotation, suggesting a more integrative online role for imagery than proposed by the target article.

Three points extend the authors' comprehensive and provocative argument: (1) The idea of “entering a community of minds” is suggested to replace theory of mind or social understanding; (2) learning words and concepts through a Wittgensteinian process often involves a period of “use without meaning”; (3) concepts based in social interaction are achieved through collaborative – neither individual nor social alone – construction.

Although an excellent review, the target article displays a bias in favor of reciprocity-based explanations and against alternatives. Tolerated scrounging is more subtle and pervasive than portrayed here. Costly signaling need not be limited to public displays and generalized sharing. The theoretical basis for extensive sharing and other forms of collective action remains unresolved, and standard reciprocity-based explanations are insufficient.