In the analysis of intergenerational transfer, several improvements can be made. First, following kin selection theory, grandparents have kin other than grandchildren in which to invest and therefore any investigation into grandparents should take this perspective. Secondly, how transfers actually enhance the survivorship of younger relatives such as grandchildren must be better measured, especially in the ethnographic literature. Finally, the problem of indirect investments or targeting must be considered.

Neural reuse posits development of functional overlap in brain system circuits to accommodate complex evolutionary functions. Evolutionary adaptation evolved neural circuits that have been exploited for many uses. One such use is engaging cognitive processes in memory consolidation during the neurobiological states of sleep. Neural reuse, therefore, should not be limited to neural circuitry, but be extended to include sleep-state associated memory processes.

Research on the early development of fundamental cognitive and language capacities has focused almost exclusively on infants from middle-class families, excluding children living in poverty who may experience less cognitive stimulation in the first years of life. Ignoring such differences limits our ability to discover the potentially powerful contributions of environmental support to the ontogeny of cognitive and language abilities.

Kinship systems are best explained functionally, in terms of the conflicting needs of the society concerned, rather than in terms of universal constraints, whether Optimality Theory or other; but OT is particularly unsuitable as it rules out taxonomies. A conceptual analysis of kinship terminology shows, not that “grammar” extends to kinship, but that general cognition has the formal power to handle grammar.

This commentary raises general questions about the parsimony and generalizability of the SIMS model, before interrogating the specific roles that the amygdala and eye contact play in it. Additionally, this situates the SIMS model alongside another model of facial expression processing, with a view to incorporating individual differences in emotion perception.

The target article emphasizes the need to identify psychological mechanisms underlying grandparental investment, particularly in low-risk family contexts. We extend this approach by addressing the changing demands of balancing work and family in low-risk families. Taking a lifespan psychological perspective, we identify additional motivators and potential benefits of grandparental investment for grandparents themselves and for subsequent generations.

In addition to questions of the representativeness of Western, educated samples vis-à-vis the rest of humanity, the prevailing practice of studying individuals who are culturally similar to the investigator entails the problem that key features of the phenomena under investigation may often go unrecognized. This will occur when investigators implicitly rely on folk models that they share with their participants.

We argue that the meaning of smiles is interpreted from physical/contextual cues, and simulation may simply reinforce the information derived from these cues. We suggest that, contrary to the claim of the SIMS model, positive and negative smiles may invoke similar simulation processes. Finally, we provide alternative explanations for the role of eye contact in the processing of smiles.

We taxonomize the varieties of representational reuse and point out that all the sorts of reuse that the brain engages in (1) involve something like a model (or schema or simulator), and (2) are effected in bodily and external media, as well as neural media. This suggests that the real fundamental organizational principle is not neural reuse, but model reuse.

Explanations in the domain of kinship can be sought on several different levels: Jones addresses online processing, as well as issues of origins and innateness. We argue that his framework can more usefully be applied at the levels of developmental and historical change, the latter especially. A phylogenetic approach to the diversity of kinship terminologies is most urgently required.

This commentary suggests that there is more continuity in pre- and post-demographic transition populations with respect to grandparental investments than is assumed by Coall & Hertwig (C&H). Recent research employing high-quality data supports the claim that sex-biased grandparental investments are likely to exist in industrialized societies, and that the economic status of grandparents is related to their long-term fitness.

Niedenthal et al. discuss the importance of eye gaze in embodied simulation and, more globally, in the processing of emotional visual stimulation (such as facial expression). In this commentary, we illustrate the relationship between oriented eye movements, consciousness, and emotion by using the case of severely brain-injured patients recovering from coma (i.e., vegetative and minimally conscious patients).

Jones's analysis of Seneca kinship semantics gets some of the facts about close relatives wrong, and his mechanism for extending the analysis to distant relatives does not work.

We argue that Anderson's “massive redeployment hypothesis” (MRH) needs further development in several directions. First, a thoroughgoing criticism of the several “embodied cognition” alternatives is required. Second, the course between the Scylla of full holism and the Charybdis of structural-functional modularism must be plotted more distinctly. Third, methodologies better suited to reveal brain circuits must be brought in. Finally, the constraints that naturalistic settings provide should be considered.

I argue that the right choice of subject pool is intimately linked to the research question. At least within economics, students are often the perfect subject pool for answering some fundamental research questions. Student subject pools can provide an invaluable benchmark for investigating generalizability across different social groups or cultures.

Presenting evidence from the social brain, we argue that neural reuse is a dynamic, socially organized process that is influenced ontogenetically and evolutionarily by the cultural transmission of mental techniques, values, and modes of thought. Anderson's theory should be broadened to accommodate cultural effects on the functioning of architecturally similar neural systems, and the implications of these differences for reuse.

We dispute Henrich et al.'s analysis of cultural differences at the level of a narrow behavioral-expression for assessing a universalist argument. When Researchers Overlook uNderlying Genotypes (WRONG), they fail to detect universal processes that generate observed differences in expression. We reify this position with our own cross-cultural research on self-enhancement and self-esteem.

Common to language and kinship is digital format. This is a discovery, not an innate feature of human cognition. But to produce a testable model, we need Darwinian behavioural ecology.

Niedenthal et al. postulate that eye contact with the expresser of an emotion automatically initiates embodied simulation. Our commentary explores the generality of such an eye contact effect for emotions other than happiness. Based on the appraisal theory of emotion, we propose that embodied simulation may be reinforced by mutual or averted gaze as a function of emotional context.

Coall & Hertwig (C&H) suggest that, because grandparental investments do not impact on child mortality in low-risk societies, fitness effects are not plausible any more. We found that grandparental investments could very well alleviate contemporary constraints on fertility. Cultural factors may influence both the occurrence and impact of grandparental investments.