Gestural communication in children and chimpanzees

1. Gestural communication in children and chimpanzees

2. Humans communicate with each other in unique ways. • Most obviously, linguistically, with socially learned, intersubjectively shared symbols • But also gesturally. Many of the most important gestures humans use - e.g., for greeting or leaving, for threatening or insulting, for agreeing or disagreeing - are also socially learned, intersubjectively shared, symbolic conventions that vary across cultures in much the same way as linguistic symbols. • This requires both ‘mindreading’ (theory of mind) and the ability/motivation to cooperate with others. Tomasello (in press); Tomasello, Carpenter, & Liszkowski (submitted)

3. Outline • Development • Theoretical issues • Pointing • Pointing basics • Infants • Apes • Children with autism

4. Development of communication in infants Adamson (1996); Carpenter, Nagell, & Tomasello (1998)

5. Development of communication in infants Adamson (1996); Carpenter, Nagell, & Tomasello (1998)

6. Development of communication in infants Adamson (1996); Carpenter, Nagell, & Tomasello (1998)

7. Theoretical debate • ‘Lean’ versus ‘rich’ interpretations of gestures in 12-month-old infants and apes • social-cognitive understanding: • lean: just trying to achieve certain behavioral effects in others (see others as causal but not mental agents; influence behavior) • rich: attempting to influence the intentional/mental states of others (transfer a mental message; influence mind) • motivation: • lean: to achieve own goals (e.g., get object or attention from adult) • rich: also for others (inform, help, share); cooperative structure Tomasello (in press); Tomasello, Carpenter, & Liszkowski (submitted)

8. Pointing basics • In itself, pointing is nothing. When faced with a pointing finger, most animals and very young infants simply stare at the finger. • Even understanding the directional nature of pointing is not enough to comprehend a full communicative act. It is possible to follow someone’s point but not know what he means by it. To illustrate: Tomasello (in press); Tomasello, Carpenter, & Liszkowski (submitted)

9. Tomasello, Call, & Gluckman (1997);see Call & Tomasello (2005) for a review • In a food finding context, a human points to one of two opaque containers. • Apes follow the point - but then choose randomly.

10. Why? • Either apes don’t know what E was directing their attention to (exactly what E was referring to), or else they don’t know whyE was directing them to it (what E’s motive was). • what: precise referent is not bucket as physical object but bucket as location of food • why: not just to show bucket, to inform them of the location • Pointing can be incomprehensible without some form of shared context or ‘common ground.’ To correctly identify the referent, the recipient needs to assume the point is relevant to something she and the pointer share. Tomasello (in press); Tomasello, Carpenter, & Liszkowski (submitted)

11. Importance of shared context (what + why)

12. Importance of shared context (what + why)

13. Shared context can help you determine what the other is pointing to (and often why) • Expressions of attitude can also help you determine why.

14. Attitude (observable cue to motive – why?)

15. Attitude (observable cue to motive – why?)

16. More pointing basics • A pointer thus combines an act of reference with an expression of motive, with the desire that the recipient attend to both of these, and from this infer the pointer’s overall intention - what the pointer wants the recipient to do - by finding some relevance to their common ground. • involves understanding of intentions and shared experience • This entire process is inherently collaborative: communicator and recipient work together to identify the intended referent, as well as the pointer’s larger intention (Clark, 1996). Tomasello (in press); Tomasello, Carpenter, & Liszkowski (submitted)

17. More pointing basics • Cooperative communicative acts involve an additional type of intention as well: a communicative intention or intention about the communication specifically (Grice, 1957; Sperber & Wilson, 1986). • When a person points to a tree for me, she not only wants me to notice the tree, she also wants me to notice her desire that I notice the tree. This additional tier is necessary to instigate in me the kinds of relevance inferences required to identify the communicator's reason for communicating (her motive). • if instead she leans back and I see the tree, I don’t need to make those kinds of inferences Tomasello (in press); Tomasello, Carpenter, & Liszkowski (submitted)

18. More pointing basics She intends that I attend to X (and wants us to know this together) for some reason relevant to our common ground. Tomasello (in press); Tomasello, Carpenter, & Liszkowski (submitted)

19. More pointing basics She intends that I attend to X (and wants us to know this together) for some reason relevant to our common ground. Apes do have some understanding of others intentions and attention. Either: • do not have a joint attentional frame (common ground) with the human that enables them to determine reference; (She’s pointing to the bucket. I’m searching for the grape – I don’t care about the bucket.) • do not understand the communicative intention, i.e., that the human wants them to know that she has an intention with respect to them; or • do not understand the informing/helping motive (cooperative intention) of the human in this situation. Tomasello (in press); Tomasello, Carpenter, & Liszkowski (submitted)

20. Complexity of pointing

21. Complexity of pointing: Adult examples Tomasello, Carpenter, & Liszkowski (submitted)

22. Complexity of pointing: Infant examples (11-13 months) Carpenter et al. (in preparation); Tomasello, Carpenter, & Liszkowski (submitted)

23. Complexity of infant pointing • Many motives, meanings • important because classically infant pointing was thought to have only two main functions: • imperative: to request objects • declarative: to share attention and interest to objects or events • ape ‘pointing’ apparently only imperative

24. Complexity of pointing: Infant examples (11-13 months) Carpenter et al. (in preparation); Tomasello, Carpenter, & Liszkowski (submitted)

25. Complexity of infant pointing • Many motives, meanings • important because classically infant pointing is thought to have only two main functions: • imperative: to request objects • declarative: to share attention and interest to objects or events • ape ‘pointing’ only imperative (?) • Absent referents • important because this is taken to be a hallmark of uniquely human language; also evidence that it is communication on a mental level

26. Complexity of pointing: Infant examples (11-13 months) Carpenter et al. (in preparation); Tomasello, Carpenter, & Liszkowski (submitted)

27. Complexity of infant pointing • Many motives, meanings • important because classically infant pointing is thought to have only two main functions: • imperative: to request objects • declarative: to share attention and interest to objects or events • ape ‘pointing’ only imperative (?) • Absent referents • important because this is taken to be a hallmark of uniquely human language; also evidence that it is communication on a mental level • Natural observations are interesting but experiments are needed.

28. Experiments • Common ground • Informative (helping) motive • Absent referents • Communicative intention

29. Common ground • Infants begin participating in joint attentional engagement by 9 months (more on that tomorrow) • By 14 months, they can use joint attentional frames/common ground to interpret others’ points.

30. Behne, Carpenter, & Tomasello (2005) • 14- to 24-month-olds • Following a visible ‘hiding’ warm-up, E hid a toy in one of two opaque containers. • E indicated the toy’s location by pointing or gazing at the correct container. • Even the youngest infants chose the correct container more often than chance.

31. Liebal, Behne, Carpenter, & Tomasello (in preparation) that adult pointed • 18-month-olds • In each of two Common Groundconditions, infants participated in a different shared activity (cleaning up or stacking) with an adult, then that adult pointed (“There!”) at a target object. • In a third, No Common Ground condition, to test whether infants were really using common ground, infants shared a frame with one adult and then a different adult pointed (“There!”). a different adultpointed

32. Liebal, Behne, Carpenter, & Tomasello (in preparation) • Even though the adults pointed in exactly the same way in each condition, infants interpreted the point differently depending on the common ground they shared with the adult: • In the Common Ground conditions, infants’ responses were appropriate to the previous shared activity. • In the No Common Ground condition, they continued the previous activity less than in the corresponding Common Ground condition, instead mostly interpreting the new adult’s point as a declarative. • Infants used their common ground with specific partners to interpret their partners’ gestures.

33. Complexity of infant pointing • Many motives, meanings • important because classically infant pointing is thought to have only two main functions: • imperative: to request objects • declarative: to share attention and interest to objects or events • Infants do point imperatively and declaratively (more on this tomorrow). They also point to inform others of things they do not know.

34. Liszkowski, Carpenter, Striano, & Tomasello (2006) • 12- and 18-month-olds • Infants watched E repeat an action (e.g., punching holes) with a target object. • The target and a distractor object were displaced. • E began looking around. • Infants pointed to inform the adult about the location of the object she was looking for.

35. Complexity of infant pointing • Common ground • Many motives, meanings, including to inform others. • Absent referents • important because this is taken to be a hallmark of uniquely human language; also evidence that it is communication on a mental level

36. Liszkowski, Carpenter, & Tomasello (submitted) Referent Present Phase Attend Event Attend Screen • 12-month-olds • A puppet appeared; E attended and emoted (positively or neutrally) either to it or to the blank screen on the other side. After the puppet disappeared, E turned to the infant. • In the first phase, infants pointed more often when E attended to the screen than to the puppet (to inform). • Infants also pointed when the referent was absent, differentially depending on how E had reacted before. Referent Absent Phase

37. Complexity of infant pointing • Common ground • Many motives, meanings, including to inform others. • Absent referents • Understanding of communicative intention (tree example)

38. Behne, Carpenter, & Tomasello (2005): control condition • E ‘pointed’ or gazed to the correct container but in a distracted, non-communicative manner. • In this condition, children performed at chance levels.

39. Theoretical debate • ‘Lean’ versus ‘rich’ interpretations of gestures in 12-month-old infants and apes • social-cognitive understanding: • lean: just trying to achieve certain behavioral effects in others (see others as causal but not mental agents; influence behavior) • rich: attempting to influence the intentional/mental states of others (transfer a mental message; influence mind) • motivation: • lean: to achieve own goals (e.g., get object or attention from adult) • rich: also for others (inform, help, share); cooperative structure Tomasello (in press); Tomasello, Carpenter, & Liszkowski (submitted)

40. Infants • Communication on mental instead of behavioral level  • Evidence (already reviewed) of understanding of attention and intentions by 12 months • Absent referents (Liszkowski et al., submitted) • Misunderstandings • Shwe & Markman (1997): when 2½-year-olds request something from an adult, and the adult misunderstands but gives them what they wanted anyway, they still attempt to correct the misunderstanding. This suggests that they had both the goal of getting the object and the goal of having the adult understand their message or communicative intention. • Prosocial motivations  • to achieve own goals, of course, but also prosocial: to inform (help), to share.

41. Apes • Communication on mental or behavioral level ? • Evidence (already reviewed) of understanding of perception and goals - but not attention and intentions (?) • not much (if any) gesturing about absent referents in non-language-trained apes • No prosocial motivations  • to achieve own goals only; no evidence of gesturing to inform (help others, without benefit for themselves) or share (tomorrow).

42. Children with autism • Communication on mental or behavioral level ? • Evidence (already reviewed) of understanding of perception and goals- but not attention and intentions (?) • ? • No prosocial motivations  • probably to achieve own goals only; no evidence of gesturing to share (no studies on informing). • Also general difficulties with communicative intentions (e.g., common ground, ‘language of the eyes’; see Sabbagh, 1999, for a review).

43. Summary • By 12 months, when they first begin pointing, infants already show the basics of uniquely human communication, supporting the ‘rich’ view. • Support for the social-pragmatic view of language acquisition (Bruner, Tomasello, etc.) • More studies are needed, but so far, ‘leaner’ interpretations of communication in apes and children with autism fit best.

45. Hare and Tomasello (2004) hid food in one of two buckets and then, in one condition, pointed to the bucket containing the food in order to inform the ape where it was. In this case, as in previous studies, the apes searched randomly. The novelty was in the second condition. Here E began by establishing with each ape a competitive relationship over the food, and then later reached toward one of the two buckets in a vain attempt to open it (the reaching was impeded). Now, surprisingly, even though the superficial behavior of the human was highly similar to that in the pointing condition - in both cases the human stretched out his arm toward the correct location - the apes in this condition suddenly knew where the food was. In this case, the apes had to discern the goal of the human - to get into that bucket - and then infer why he wanted to do this: because there is something good inside. This cognitive process is quite complex on its own terms, but the key point is that it includes none of the crucial elements of shared intentionality from our analysis of the interpersonal structure of pointing. The apes' understanding of the human's reaching is of individual goals or intentions toward things, not communicative goals or intentions toward themselves. There is thus no question of a joint attentional frame or common ground, or of communicative or referential intentions, or of any assumptions of helpfulness or other interpersonal motives. • Following Tomasello et al. (2005), we may thus attempt to characterize the essential elements in the comprehension and expression of human pointing as a communicative act by viewing them from the perspective of shared intentionality. Whereas apes' understanding of the goal of a reaching person is essentially an act of individual cognition, humans' understanding that others are pointing out things for them because of their presumed relevance to some common ground or joint attentional frame is an act of interpersonal cognition involving shared attention and knowledge, along with some motive for helping or sharing with others.

46. Infants Chimpanzees • Infants pass this test.