We argue that the lack of large cross-cultural differences in many games with student subjects from developed countries may be due to the nature of the games studied. These games tap primarily basic psychological reactions, like fairness and reciprocity. Once we look at norm-enforcement, in particular punishment, we find large differences even among culturally rather homogeneous student groups from developed countries.

This commentary argues that one specific but central concept in Lewis's theory, circular causality, is fundamentally flawed and should be discarded – first, because it does not make theoretical sense, and, second, because it leads to problems in practice, such as confounding the interaction between different systems with the relationship between different levels of analysis of a single system.

Bridging between psychological and neurobiological systems requires that the system components are closely specified at both the psychological and brain levels of analysis. We argue that in developing his dynamic systems theory framework, Lewis has sidestepped the notion of a psychological level systems model altogether, and has taken a partisan approach to his exposition of a brain-level systems model.

The interesting and deep commentaries on our target article reflect the continued high interest in the problem of colour categorisation and naming. Clearly, colour remains for many cognitive science related disciplines a fascinating microworld in which some of the most fundamental issues for cognition and culture can be studied. Although our target article took the stance of practically oriented engineers who are trying to find the best solution for orchestrating the self-organisation of communication systems in artificial agents, most commentators focus on the implications for cognitive science and we will do the same in our reply.

The Ultimatum Game is commonly interpreted as a two-person bargaining game. The third person who donates and may withdraw the money is not included in the theoretical equations, but treated like a neutral measurement instrument. Yet in a cross-cultural analysis it seems necessary to consider the possibility that the thoughts of a player – strategic, altruistic, selfish, or concerned about reputation – are influenced by both an anonymous second player and the non-anonymous experimenter.

It is suggested that Walker's consolidation-based enhancement of memory during REM sleep corresponds to the simulated annealing technique used for function optimization, and that robotic and AI design could benefit from inclusion of a deliberate REM-like memory optimization phase.

steels & belpaeme (s&b) are clearly interested in the possible test their models may provide for human language theories. however, they only superficially address the assumptions underlying their own agent architecture, while these are of crucial relevance to the topic of human language. these assumptions fit an augustinian picture of language, which wittgenstein challenges in his philosophical investigations. it is too early to draw conclusions regarding human language evolution from such models.

We agree that motivation to share emotions and other mental states is crucial for communicative development, but human infants are highly selective in sharing mental states, and this is well taken evolutionarily. Young chimpanzees may also have motivation to imitate mothers. Thus, uniquely human cognition and culture may not be reduced to a few basic abilities and/or inclinations.

trust is a temporary attachment between humans that pervades our daily lives. recent research has shown that the affiliative hormone oxytocin rises with a social signal of interpersonal trust and is associated with trustworthy behavior (the reciprocation of trust). this commentary reports these results and relates them to the target article's findings for variations in affiliative-related behaviors.

Decay gradients are usually drawn facing the wrong direction. Righting them emphasizes the role of stimuli that mark the response, and leads to different inferences concerning the factors controlling response– reinforcer associations. A simple model of the concatenation of stimulus traces provides some insight to the problems of impulse control relevant to ADHD.

Walker's target article proposes a refinement of the well known two-stage model of memory formation to explain the positive effects of sleep on consolidation. After a first stage in which a labile memory representation is formed, a further stabilisation of the memory trace takes place in the second stage, which is dependent on (REM) sleep. Walker has refined the latter stage into a stage in which a consolidation-based enhancement occurs. It is not completely clear what consolidation-based enhancement implies and how it can be dissociated from a stage for memory-stabilisation. A more serious consideration, however, is whether a second stage in memory consolidation that is solely dependent on sleep, is really necessary. The classical, passive, interference theory is able to explain adequately the findings related to the effects of sleep and memory, and can lead perhaps better to an understanding of the highly variable data in this field.

Self-organizing dynamic systems (DS) modeling is appropriate to conceptualizing the relationship between emotion and cognition-appraisal. Indeed, DS modeling can be applied to encompass and integrate additional phenomena at levels lower than emotional interpretations (genes), at the same level (motives), and at higher levels (social, cognitive, and moral emotions). Also, communication is a phenomenon involved in dynamic system interactions at all levels.

heuristics are necessary but far from sufficient explanations for moral judgment. this commentary stresses: (a) the need to complement cold, cognitive-economizing functionalist accounts with hot, value-expressive, social-identity-affirming accounts; and (b) the importance of conducting reflective-equilibrium thought and laboratory experiments that explore the permeability of the boundaries people place on the “thinkable.”

The predictive validity of the ultimatum game (UG) for cross-cultural differences in real-world behavior has not yet been established. We discuss results of a recent meta-analysis (Oosterbeek et al 2004), which examined UG behavior across large-scale societies and found that the mean percent offers rejected was positively correlated with social expenditure.

Tomasello et al. provide a convincing account of the origins of cultural cognition. I highlight how emotionally grounded sharing of experiences (not merely or predominantly intentions) is critical for the development of interpersonal understanding and perspective-sensitive thinking. Such sharing is specifically human in quality as well as motivation, and entails forms of self–other connectedness and differentiation that are essential to communication and symbolic functioning.

Tomasello et al. propose that shared intentionality is a uniquely human ability. In light of this, we discuss several cultural behaviors that seem to result from a motivation to share experiences with others, suggest evidence for coordination and collaboration among chimpanzees, and cite recent findings that counter the argument that the predominance of emulation in chimpanzees reflects a deficit in intention reading.

I argue that altruistic behavior and its variation across cultures may be caused by mental cognitive mechanisms that induce cooperative behavior in contract-like situations and adapt that behavior to the kinds of contracts that exist in one's socio-cultural environment. I thus present a cognitive alternative to Henrich et al.'s motivation-based account. Rather than behaving in ways that reveal preferences, subjects interpret the experiment in ways that cue their social heuristics. In order to distinguish the respective roles of preferences and cognitive processes that determine economic behavior, we need more ethnography of strategies “in the wild.”

Understanding how emotions emerge is difficult without determining what characteristic of the trigger actually triggers them. Knowing whether emotional experiences self-stabilize is difficult without remembering what other processes are set in play as the emotion emerges. It is not clear either that positive feedback is required for the emergence of emotion or that an attractor model captures well what is happening when an emotion arises.

Following Karni's seminal work, Walker and other researchers have recently provided gradually convincing evidence that sleep is critical for the consolidation-based enhancement (CBE) of motor sequence learning. Studies in our laboratory using a motor adaptation paradigm, however, show that CBE can also occur after the simple passage of time, suggesting that sleep effects on memory consolidation are task-related, and possibly dependent on anatomically dissociable circuits.

vallortigara & rogers (v&r) propose a fundamental role of the environment in determining population-level lateralisation and suggest that genes play no primary function in this phenomenon. here i argue that genes involved in the coordination of visceral organ laterality and in coupling of different forms of lateralisation do play a role in the control of lateralisation within the population.