Both distributed coding, with its implication of neural reuse, and more specialized function have been recognized since the beginning of brain science. A controversy over imageless thought threw introspection into disrepute as a scientific method, making more objective methods dominate. It is known in information science that one element, such as a bit in a computer, can participate in coding many independent states; in this commentary, an example is given.

Grandparental altruism may be partially understood in the same way as other instances of altruism. Acts of altruism often occur in a context in which the actor has a broader sense of cause and effect than is evident in more typical behavioral interactions where cause and effect appear relatively transparent. Many believe that good deeds will ultimately produce good results.

The assumption that a complex and fuzzy notion like smile can be the basis of a scientific, rather than semantic, inquiry can only lead to confused and inconclusive results. It would be more productive to start with the well-defined and measurable patterns of the clearly visible contrasts that are produced on the human face by various muscular contractions around the white patches formed by the sclera and the teeth. These features are universal, whereas a common word, in whatever language, is necessarily ambiguous, culture-dependent, and historically rather than biologically determined.

The quest to understand “what makes us human” has been heading towards an impasse, when comparative psychology compares primarily individuals that are not representative of their species. Captives experience such divergent socioecological niches that they cannot stand for their wild counterparts. Only after removing ethnocentrism and anthropocentrism will we be able to progress in our understanding of “what makes us human.”

The target paper claims to contribute to the conceptualisation of kinship but is, in fact, only concerned with descriptive kinship terminologies. It uses Optimal Theory to analyse this vocabulary but it is not clear if this is to be understood as a psychological phenomenon. Jones does not make clear how this special vocabulary might relate to kinship in general.

Integral to the discipline of anthropology are both science and holism. The application of Optimality Theory to two partial kin terminologies narrows analysis to descriptive value, fragments phenomena, and constrains data selection, which precludes significant knowledge. Embedded in this critique is a call to move analysis from fragment to whole and from descriptive features to deeper levels of knowledge underlying kin terms, thereby leading to a cognitive path for holistic understanding of human phenomena.

We argue that Henrich et al. do not go far enough in their critique: Sample diversification, while important, will not lead to the detection of generalizable principles. For that it will be necessary to broaden the range of contexts in which data are gathered. We demonstrate the power of contexts to alter results even in the presence of sample diversification.

Anderson suggests that theories of sensorimotor grounding are too narrow to account for his findings of widespread “reuse” supporting multiple different cognitive “task domains.” I call some of the methodological assumptions underlying this conclusion into question, and suggest that his examples reaffirm rather than undermine the special status of sensorimotor processes in cognitive evolution.

The embodied simulation of smiles involves motor activity that often changes the perceivers' own emotional experience (e.g., smiling can make us feel happy). Although Niedenthal et al. mention this possibility, the psychological processes by which embodiment changes emotions and their consequences for processing other emotions are not discussed in the target article's review. We argue that understanding the processes initiated by embodiment is important for a complete understanding of the effects of embodiment on emotion perception.

Selection on grandparental investment is more complex than Coall & Hertwig (C&H) propose. Patterns of investment are subject to an intergenerational conflict over how resources should be distributed to maximize fitness. Grandparents may be selected to distribute resources unevenly, while their descendants will be selected to manipulate investment in their own favor. Here we outline the evolutionary basis of this conflict.

Understanding the very nature of the smile with an integrative approach and a novel model is a fertile ground for a new theoretical vision and insights. However, from this perspective, I challenge the authors to integrate culture and race in their model, because both factors would impact upon the embodying and decoding of facial expressions.

The compelling case that Anderson makes for neural reuse and against modularity as organizing principle of the brain is further supported by evidence from developmental disorders. However, to provide a full evolutionary-developmental theory of neural reuse that encompasses both typical and atypical development, Anderson's “massive redeployment hypothesis” (MRH) could be further constrained by considering brain development across ontogeny.

We suggest that there are two coordination games when it comes to understanding kin terminology. Jones' article focuses on the linguistic coordination inherent in developing meaningful kin terminologies, alluding briefly to the benefits of these kin terminologies for coordination in other domains. We enhance Jones' discussion by tracing the links between the structure of kin terminologies and their functions.

What makes the question of grandparental investment so very interesting is trying to tease out the underlying motivations. Grandparental investment is variable and grandparental altruism, if it exists at all, is also variable. Neither evolutionary theory nor rational choice theory has an easy time explaining this variation, and insight is further impeded by the absence of any compelling empirical studies designed for the purpose of testing alternative explanations of variations in grandparental investment.

Henrich et al. provide a compelling argument about a bias in the behavioral sciences to study human behavior primarily in WEIRD populations. Here we argue that brain scientists are susceptible to similar biases, sampling primarily from WEIRD populations; and we discuss recent evidence from cultural neuroscience demonstrating the importance and viability of investigating culture across multiple levels of analysis.

Coall & Hertwig (C&H) bring attention to alternative accounts of grandparental investment from economics, evolutionary anthropology, psychology, and sociology, which have yet to be reconciled. We attempt to help integrate some of the disparate perspectives by expanding the scope of the evolutionary perspective, highlighting some gaps, and discussing problems with the authors' treatment of grandparents in traditional societies.

Smiling can be interpreted as a costly signal of future benefits from cooperation between the individual smiling and the individual to whom the smile is directed. The target article by Niedenthal et al. gives little attention to the possible mechanisms by which smiling may have evolved. In our view, there are strong reasons to think that smiling has the key characteristics of a costly signal.

Henrich et al.'s conclusion that psychologists ought not assume uniformity of psychological phenomena depends on their descriptive claim that there is no pattern to the great diversity in psychological phenomena. We argue that there is a pattern: uniformity of learning processes (broadly construed), and diversity of (some) mental contents (broadly construed).

The target article offers an analysis of the categorization of kin types and empirical evidence that cross-cultural universals may be amenable to OT explanation. Since the analysis concerns the structuring of conceptual categories rather than the use of words, it differs from previous OT analyses in lexical semantics in what is considered to be the input and output of optimization.

We isolate some critical aspects of the reuse notion in Anderson's massive redeployment hypothesis (MRH). We notice that the actual rearranging of local neural circuits at a timescale comparable with the reactivity timescale of the organism is left open. We propose the concept of programmable neural network as a solution.