In their account of the origins of human collaborative abilities, Tomasello et al. rely heavily on reasoning and evidence from adult–child collaborations. Peer collaborations are not discussed, but early peer collaborations differ from early adult–child collaborations. Describing and explaining the similarities and differences in shared intentionality with peers and adults will bring us closer to understanding the developmental mechanisms.

Tomasello et al. point up the mutual interdependency of the unique human capacity for intersubjectivity and the evolution and institutionalization of culture. Since both intersubjectivity and cultural cooperation require localized knowledge, Homo sapiens is highly reliant on such knowledge and in that sense is a highly localized species, requiring special means to surmount cultural misreadings and to achieve translocal, or global, interconnection.

Tomasello et al. highlight how in combination cognitive impairments and affective impairments help explain why individuals with autism do not enter fully into human culture. We query whether the motivational component is a later development in human ontogeny and whether the cognitive level of intention reading is intact in autism. A key question is what neuropsychological impairments underlie this cognitive–affective impairment.

This commentary analyzes the target article to determine whether shared-intention development could be implemented and tested in robotic systems. The analysis indicates that such an implementation should be feasible and will likely rely on a construction-based approach similar to that employed in the construction grammar framework.

Numerous questions remain unanswered concerning the functional determinants of symbolic behavior and perspective-taking, particularly regarding the capabilities of children with autism. An alternative approach that considers these behaviors to be forms of derived relational responding allows for the design of functional intervention programs to establish such repertoires in individuals for whom they are absent.

In the dyadic and triadic sharing of emotions, intentions, and behaviors in families, interactive synchrony is important to the early life experiences that contribute to the development of cultural cognition. This synchrony likely depends on neurobiological circuits, currently under study with brain imaging, that involve attention, stress response, and memory.

Two aspects of Tomasello et al.'s account would benefit from further elaboration: (1) the construction of dialogic cognitive representations through social interaction, and (2) the cognitive consequences of operating with such representations. Vygotskian ideas on internalisation and verbal mediation may help us better to understand how dialogic cognitive representations can transform human cognition.

Sound comparative psychology and modern evolutionary and developmental biology (often called evo-devo) emphasize powerful effects of developmental conditions on the expression of genetic endowment. Both demand that evolutionary theorists recognize these effects. Instead, Tomasello et al. compares studies of normal human children with studies of chimpanzees reared and maintained in cognitively deprived conditions, while ignoring studies of chimpanzees in cognitively appropriate environments.

Four issues that build on the ideas offered by Tomasello et al. are discussed: the developmental course of shared intentionality and its relation to other developing abilities and experiences, and the conceptualization of three key features of the process: motivation, plans and the development of planning, and culture.

Tomasello et al.'s two prerequisites, we argue, are not sufficient to explain the emergence of Joint Collaboration. An adequate account must include the human-specific capacity to communicate relevant information (that may have initially evolved to ensure efficient cultural learning). This, together with understanding intentional actions, does provide sufficient preconditions for Joint Collaboration without the need to postulate a primary human motive to share others' psychological states.

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.

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.

We agree that human culture is unique. However, we also believe that an understanding of the evolution of culture requires a comparative approach. We offer examples of collaborative behaviors from dolphin play, and argue that consideration should be given to whether various forms of culture are best viewed as falling along a continuum or as discrete categories.

Tomasello et al. have not characterized the motivation underlying shared intentionality, and we hope to encourage research on this topic by offering comparative paradigms and specific empirical questions. Although we agree that nonhuman primates differ greatly from us in terms of shared intentionality, we caution against concluding that they lack all aspects of it before other empirical tools have been exhausted. In addition, identifying the conditions in which humans spontaneously engage in shared intentionality, and the conditions in which we fail, will more fully characterize this ability.

Shared knowledge of intentionality as well as shared knowledge of anything depends on the organism's understanding of itself, others, and the possible relations between self and other. This understanding involves mental representations of me, which emerges in the second half of the second year in the human infant, and it is this ability that gives rise to humanlike social understanding and complex self-conscious emotions.

Tomasello et al. provide a new account of cultural uniqueness, one that hinges on a uniquely human motivation to share intentionality with others. We favor an alternative to this motivational account – one that relies on a modular explanation of the primate intention-reading system. We discuss this view in light of recent comparative experiments using competitive intention-reading tasks.

Tomasello et al. argue that cultural cognition derives from humans' unique motivation to share psychological states. We suggest that what underlies this motivation is children's propensity to seek out the underlying causes of behavior. This propensity, combined with children's competence at it, makes them especially skillful at acquiring the intentional, conventional, and reliable forms that constitute culture.

Research on the affective and neurodevelopmental correlates of infant joint attention skills support several of the hypotheses raised by Tomasello et al. regarding the development of the capacity to share intention with others. In addition, research and theory suggests that self-awareness and self-regulatory processes may play a role in the development of this vital human ability domain.

Evidence for infants' sensitivity to behavior being goal oriented leaves it open as to whether they see such behavior as being designed to lead to an external goal or whether they see it, in addition, as being directed by an internal representation of the goal. We point out the difficulty of finding possible criteria for how infants or children view this matter.