By examining single-word reading times (in full sentences read for meaning), we show that (1) function words are accessed faster than content words, independent of perceptual characteristics; (2) previous failures to show this involved problems of frequency range and task used; and (3) these differences in lexical access are related to perceptual fluency. We relate these findings to issues in the literature on event-related potentials (ERPs) and neurolinguistics.

Exclusively focused on data that are consistent with the proposed ideas, the target article misses an opportunity to review data that are inconsistent with them. Weaknesses of the emulation theory become especially evident when one tries to incorporate physiologically realistic muscle and reflex mechanisms into it. In particular, it fails to resolve the basic posture-movement controversy.

Carpendale & Lewis's (C&L's) interesting and insightful article did not integrate several potentially useful notions from emotion theory and research into their explanatory framework. I propose that emotions are indigenous elements of mind and that children's understanding of them is fundamental to their understanding of the mental life of self and others, understandings critical to the development of social and emotional competence.

The transfer of food among group members is a ubiquitous feature of small-scale forager and forager-agricultural populations. The uniqueness of pervasive sharing among humans, especially among unrelated individuals, has led researchers to evaluate numerous hypotheses about the adaptive functions and patterns of sharing in different ecologies. This article attempts to organize available cross-cultural evidence pertaining to several contentious evolutionary models: kin selection, reciprocal altruism, tolerated scrounging, and costly signaling. Debates about the relevance of these models focus primarily on the extent to which individuals exert control over the distribution of foods they acquire, and the extent to which donors receive food or other fitness-enhancing benefits in return for shares given away. Each model can explain some of the variance in sharing patterns within groups, and so generalizations that ignore or deny the importance of any one model may be misleading. Careful multivariate analyses and cross-cultural comparisons of food transfer patterns are therefore necessary tools for assessing aspects of the sexual division of labor, human life history evolution, and the evolution of the family. This article also introduces a framework for better understanding variation in sharing behavior across small-scale traditional societies. I discuss the importance of resource ecology and the degree of coordination in acquisition activities as a key feature that influences sharing behavior.

Schizophrenia is a worldwide, prevalent disorder with a multifactorial but highly genetic aetiology. A constant prevalence rate in the face of reduced fecundity has caused some to argue that an evolutionary advantage exists in unaffected relatives. Here, I critique this adaptationist approach, and review – and find wanting – Crow's “speciation” hypothesis. In keeping with available biological and psychological evidence, I propose an alternative theory of the origins of this disorder. Schizophrenia is a disorder of the social brain, and it exists as a costly trade-off in the evolution of complex social cognition. Paleoanthropological and comparative primate research suggests that hominids evolved complex cortical interconnectivity (in particular, frontotemporal and frontoparietal circuits) to regulate social cognition and the intellectual demands of group living. I suggest that the ontogenetic mechanism underlying this cerebral adaptation was sequential hypermorphosis and that it rendered the hominid brain vulnerable to genetic and environmental insults. I argue that changes in genes regulating the timing of neurodevelopment occurred prior to the migration of Homo sapiens out of Africa 100,000–150,000 years ago, giving rise to the schizotypal spectrum. While some individuals within this spectrum may have exhibited unusual creativity and iconoclasm, this phenotype was not necessarily adaptive in reproductive terms. However, because the disorder shared a common genetic basis with the evolving circuitry of the social brain, it persisted. Thus schizophrenia emerged as a costly trade-off in the evolution of complex social cognition.

High producers are motivated to hunt in spite of high levels of sharing because the transfers come from absolutely larger amounts of resource. In the context of a generalized cooperative subsistence strategy, stinginess could provoke the withdrawal of cooperative partners and result in a loss of income. Good producers could have more to lose by not sharing than poor producers would.

The cell assembly model of language posits that words are laid down in the cortex by discrete sets of neurons distributed over specific parts of the brain. The strong internal links of these “word webs” may not only bind articulatory and acoustic knowledge of a lexical item, they may also link word and meaning; for example, by connecting neuron populations related to word forms to those of actions and perceptions to which the words refer. Therefore, the cortical activation elicited by words should reflect aspects of word meaning, a postulate that has received strong support from recent work using neurophysiological and metabolic imaging. Segalowitz & Lane make the point that this neurobiological model can also be used to predict reaction times in behavioral experiments, using the behavioral distinction between content and function words as an example. We acclaim their view, but warn that response times might be related to different mechanisms at the neuronal level, including the cortical distribution and internal connectivity of cell assemblies along with their mutual connections in the grammatical (syntactic and semantic) network.

Aspects of “emulation theory” have been seminal to our understanding of spatial orientation for more than 50 years. Sometimes called internal models, existing implementations include both traditional observers and optimal observers (Kalman filters). This theoretical approach has been quite successful in helping understand and explain spatial orientation – successful enough that experiments have been guided by model predictions.

We argue that theory-of-mind understanding has developed to facilitate joint thinking and planning, defined as the creation of new mental objects that could not have been created by one mind. Three components of this ability are proposed: the mental architecture indexed by false belief understanding, domain-specific knowledge, and the prioritization of the joint mind over the individual mind.

Individuals give for two reasons. One is to get a benefit back. The other is to avoid a cost. “Cooperation” theories stress mutual benefits. “Conflict” theories stress costs. Hunters may give up part of their hunt because they get favors back, or because the recipients are stronger than they are and the hunting isn't as good anywhere else.

Gold & Stoljar are right in rejecting the radical neuron doctrine, but we argue that their distinction between determination and explanation is not principled enough to support their conclusion. We claim that the notions of multiple supervenience and screening-off offer a more precise construal of the dissociation between explanation and determination that lies at the heart of the antireductionist position.

Burns proposes an intriguing hypothesis by suggesting that the “schizophrenia genes” might not be regulatory genes themselves, but rather closely associated with regulatory genes directly involved in the proper growth of the social brain. We point out that this account would benefit from incorporating the effects of localized lesions and aberrant hemispheric asymmetry on cortical connectivity underlying the social brain. In addition, we argue that the evolutionary framework is superfluous.

Carpendale & Lewis's (C&L's) theoretical reconstruction of the “theory of mind” problem offers new hope but still has far to go. The study of atypical development may provide some useful insights for dealing with the work ahead. In particular I discuss three issues – the boundary problem, the question of end states, and the issue of the centrality of triadic interaction.

Grush makes an important contribution to a promising way of viewing mental representation: as a component activity in sensorimotor processes. Grush shows that there need be no entities in our heads that would count as representations, but that, nevertheless, the process of representation can be defined so as to include both natural and artificial (e.g., linguistic or pictorial) representing.

Much can be gained by specifying the operation of the emulation process. A brief review of studies from diverse domains, including complex motor-skill representation, emotion perception, and face memory, highlights that emulation theory offers precise explanations of results and novel predictions. However, the neural instantiation of the emulation process requires development to move the theory from armchair to laboratory.

Carpendale & Lewis's (C&L's) critique of traditional accounts of “theory of mind” is well taken, but the alternative theory they propose is premature at its best, unconvincing at its worst. The proposed theory is ad hoc and confirmatory in its findings; vague and generic in its claims; and unjustified and unnecessary in its (putative) novelty.

Dysfunctions of the neural circuits that implement social behavior are necessary but not a sufficient condition to develop schizophrenia. We propose that schizophrenia represents a disease of general connectivity that impairs not only the “social brain” networks, but also different neural circuits related with higher cognitive and perceptual functions. We discuss possible mechanisms and evolutionary considerations.

Gurven suggests that the tolerated scrounging model has limited relevance for explaining patterns of food transfers in human populations. However, this conclusion is based on a restricted interpretation of the tolerated scrounging model proposed originally by Blurton Jones (1987). Examples of food transfers in nonhuman primates illustrate that the assumptions of Gurven's tolerated scrounging model are open to question.

Illusory kinesthetic sensation was influenced by motor imagery of the wrist following tendon vibration. The imagery and the illusion conditions commonly activated the contralateral cingulate motor area, supplementary motor area, dorsal premotor cortex, and ipsilateral cerebellum. This supports the notion that motor imagery is a mental rehearsal of movement, during which expected kinesthetic sensation is emulated by recruiting multiple motor areas, commonly activated by pure kinesthesia.

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.