In their natural communication, great apes produce and comprehend many different communicative gestures and vocalizations. Particularly in the gestural modality, they do this in intentional, flexible ways, sensitive to the attentional state of the recipient (see Call & Tomasello, 2007, for a review). Apes are also very good at manipulating the behavior of humans to get what they want. Thus, apes raised in contact with humans learn to indicate objects they want (even those in hidden locations), tools they need, and places they want to go (Leavens, Hopkins & Bard, 2005). But great ape communication is still very different from human communication in terms of its most basic underlying structures and motivations. Even leaving aside language, to make the comparison fairer, human infants gesture in order to communicate with others in species-unique ways, for example, by pointing. These gestures depend fundamentally on skills and motivations of shared intentionality (Tomasello, 2006). First, human intentional communication depends fundamentally on some kind of shared common ground between communicator and audience, for example, some kind of joint attentional frame. Thus, suppose that an adult points to an opaque bucket for the infant. If he does this out of the blue, the infant cannot know whether he is pointing to direct her attention to the container’s color, its material, its contents, or any other of myriad possibilities. However, if they are playing a hiding–finding game together, and in this context the adult points to the bucket, the infant will very likely infer that he is pointing to inform her of the location of the hidden object. Fourteenmonth- old infants make just such an inference in this situation (Behne, Carpenter & Tomasello, 2005), but chimpanzees and other apes do not (see Call & Tomasello, 2005, for a review). It is important to recall that apes are very good at following gaze direction in general (including that of humans), and so their struggles in this task do not emanate from an inability to follow the directionality of the pointing cue; rather, they do not seem to understand the meaning of this cue. Because they do not share with the human the joint attentional frame (common ground) of the hiding–finding game, they follow the point to the bucket and say, in effect, ‘A bucket. So what? Now where’s the food?’ They do not understand that the pointing is intended to be ‘relevant’ to the searching as a shared activity (see Sperber & Wilson, 1986).

Second, humans also communicate for different motives than chimpanzees. Chimpanzees and other apes gesture in order to manipulate others – to get others to do what they want them to do – not, as humans, to inform others of things helpfully or to simply share experience with them. Thus, by 9 months of age, human infants have begun to direct others’ attention to objects by showing gestures in order to initiate joint attentional interactions (Carpenter, Nagell & Tomasello, 1998). By 12 months of age, infants point for others simply to share interest and attention with them (Liszkowski, Carpenter, Henning, Striano & Tomasello, 2004). In addition, 12-month-olds also point to inform others of things they do not know – in effect sharing information with them – even when there is no benefit for themselves (Liszkowski, Carpenter, Striano & Tomasello, 2006). Apes do not point for either of these reasons, even though they sometimes point to things they want humans to fetch for them (Call & Tomasello, 1994). Interestingly, even when young children are requesting things from others, their communication is collaborative in the sense that they are not just trying to get the things but instead to influence the other’s informational and goal states (Shwe & Markman, 1997). In general, chimpanzee communication involves individualistic means and motives whereas even prelinguistic human infants communicate cooperatively, and often with the sole motivation to share experiences and information with others. This difference in motivation is highlighted by a recent experiment. Hare and Tomasello (2004) compared apes’ comprehension of the pointing gesture in a hiding–finding game, as above, to their comprehension of a similar but different reaching cue in the same task. Specifically, in one condition the experimenter simply pointed cooperatively to the location of the hidden food, as before, whereas in the other condition the human first established a competitive relationship with the ape, and then subsequently reached unsuccessfully in the direction of the baited bucket (because the hole through which he reached was too small for full arm extension). In this situation, with an extended arm that resembled in many ways a pointing gesture (but with thwarted effort and without gaze alternation), apes suddenly became successful.

One interpretation is that in this situation apes understood the human’s simple (competitive) intention to get into the bucket, and from this inferred the presence of food there. But when they observed the pointing gesture, they did not understand its underlying cooperative motive – to inform them, helpfully, of the food’s location – and so the gesture had no meaning for them.