Here's the abstract of the paper:
We argue for the importance of processes of shared intentionality in children's early cognitive development. We look briefly at four important social-cognitive skills and how they are transformed by shared intentionality. In each case, we look first at a kind of individualistic version of the skill - as exemplified most clearly in the behavior of chimpanzees - and then at a version based on shared intentionality - as exemplified most clearly in the behavior of human 1- and 2-year-olds. We thus see the following transformations: gaze following into joint attention, social manipulation into cooperative communication, group activity into collaboration, and social learning into instructed learning. We conclude by highlighting the role that shared intentionality may play in integrating more biologically based and more culturally based theories of human development.
The main idea is that the ability to direct shared attention and action with another individual (often the parent or caregiver) on third objects (toys, food, etc.) is a basic ability that emerges early in human ontogeny (one- and two-year-olds) and underlies human cognitive development. This explanation attempts to transform what seems magical (humans understand what each other are saying and thinking) into a simple shift in viewpoint (human children assume that other people are thinking about something, and the rest is learning.
The "aboutness" is the "intentionality" part. An intentional mental state is one that is about something.
In all four of these domains, apes are mostly concerned with their own individual goals. They use or exploit others - by gathering information from them, manipulating them as social tools, coordinating actions with them for their own benefit - and often compete with them as well. Human children, on the other hand, often are concerned with sharing psychological states with others by providing them with helpful information, forming shared intentions and attention with them, and learning from demonstrations produced for their benefit. The emergence of these skills and motives for shared intentionality during human evolution did not create totally new cognitive skills. Rather, what it did was to take existing skills of, for example, gaze following, manipulative communication, group action, and social learning, and transform them into their collectively based counterparts of joint attention, cooperative communication, collaborative action, and instructed learning - cornerstones of cultural living. Shared intentionality is a small psychological difference that made a huge difference in human evolution in the way that humans conduct their lives (Tomasello and Carpenter 2007:124).
Chris Chatham's post has a good ending -- which raises the problem of testing this theory of human intelligence in comparison with other potential alternatives:
Although humans and non-human primates differ in a variety of seemingly more important ways (e.g., language and enhanced working memory being just two), Tomasello suggests that "shared intentionality" is the most critical: a propensity for social interaction allowed each of these other capacities to evolve to their current state. In contrast, other theorists have hypothesized other "core differences," for example the use of recursive symbols. Unfortunately, it's difficult to imagine how some of these theories could be falsified, since we have little ability to infer "recursion" or "social intention" from the archeological record of early humans, and even if such data did exist, these differences could be incidental as opposed to causal factors in the development of human intelligence.
Edmund Blair Bolles' blog "Babel's Dawn" has a new post about joint attention as a prerequisite for language, which notes an argument by Lisbeth Nielsen (2002) that shared intentionality may first emerge from shared emotional experience:
An argument is developed that supports a simulationist account about the foundations of infants' and young children's understanding that other people have mental states. This argument relies on evidence that infants come to the world with capacities to send and receive affective cues and to appreciate the emotional states of others Ã¢Â€Â“ capacities well suited to a social environment initially made up of frequent and extended emotional interactions with their caregivers. The central premise of the argument is that the foundation of infants' understanding of other minds is built upon an early-developing capacity to share others' emotion experiences. The emotion experiences elicited in interactions between caregivers and infants enable the elaboration of this primitive understanding into a more fully developed understanding of psychological subjects. The evidence presented in support of these claims derives from a wide range of studies of the phenomena of emotional contagion, affective communication, and emotion regulation involving infants, young children, and adults.
Emotion is a good candidate for early emergence of this ability -- it genuinely is early, it involves ancient facial, gestural, and vocal communication abilities, it is neurally related to pleasure and pain networks, and well-known to be linked to motivation and planning ability.
Tomasello M, Carpenter M. 2007. Shared intentionality. Dev Sci 10:121-125. doi: 10.1111/j.1467-7687.2007.00573.x
Nielsen L. 2002. The simulation of emotion experience: on the emotional foundations of the theory of mind. Phenomenol Cog Sci 1:255-286. doi: 10.1023/A:1021359916894