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A Puzzle about Pointing

So far it's been all very straightforward, but we're about to run into a puzzle.
The puzzle will help us to understand why someone might think that ‘infant pointing is best understood … is best understood … as depending on … shared intentionality’

a puzzle about pointing

\subsection{Why don’t ape’s point?}

Contrast apes with humans ...

‘there is not a single reliable observation, by any scientist anywhere, of one ape pointing for another’.

Tomasello 2006, p. 507

\citep[p.\ 507]{Tomasello:2010dy}

footnote: ‘There is actually one reported incident of a bonobo pointing for conspecifics in the wild (Veà and Sabater-Pi 1998)’

Tomasello 2006, footnote 1

‘Although some apes, especially those with extensive human contact, sometimes point imperatively for humans […],

‘no apes point declaratively ever.’

\citep[p.\ 510]{Tomasello:2010dy}

Tomasello 2006, p. 510

What does declaratively mean? Liszkowski and Tomasello call pointing declarative when its done to initiate joint engagement.

Why don’t apes point? (Tomasello’s question)

motor issues?

But they do gesture

understanding action?

But they are sensitive to facts about
the goals of others' actions.

So the discrepancy is not easily explained.
Comprehension is also missing ...
This question is the puzzle. Or, rather, it's half of the puzzle. (The other half is about why infants don't point until they're around 11 months old.)

A clue: apes don't comprehend declarative pointing ...

In this experiment, we contrast failed reaches with pointing ...
Hare and Call (\citeyear{hare_chimpanzees_2004}) contrast pointing with a failed reach as two ways of indicating which of two closed containers a reward is in. Chimps can easily interpret a failed reach but are stumped by the point to a closed container.
You are the subjects. This is what you saw (two conditions). Your task was to choose the container with the reward.
Infants can do this sort of task, it's really easy for them \citep{Behne:2005qh}. (And, incidentally, they distinguish communicative points from similar but non-communicative bodily configurations.)
The pictures in the figure stand for what participants, who were chimpanzees, saw.
The question was whether participants would be able to work out which of two containers concealed a reward.
In the condition depicted in the left panel, participants saw a chimpanzee trying but failing to reach for the correct container.
Participants had no problem getting the reward in this case, suggesting that they understood the goal of the failed reach.
In the condition depicted in the right panel, a human pointed at the correct container.
Participants did not get the reward in this case as often as in the failed reach case, suggesting that they failed to understand the goal of the pointing action.
(Actually the apes were above chance in using the point, just better in the failed reach condition. Hare et al comment ;chimpanzees can learn to exploit a pointing cue with some experience, as established by previous research (Povinelli et al. 1997; Call et al. 1998, 2000), and so by the time they engaged in this condition they had learned to use arm extension as a discriminative cue to the food’s location' \citep[p.\ 578]{hare_chimpanzees_2004}.)
\footnote{ The contrast between the two conditions is not due merely to the fact that one involves a human and the other a chimpanzee. Participants were also successful when the failed reach was executed by a human rather than another chimpanzee \citep[][experiment 1]{hare_chimpanzees_2004}. }
\textbf{Note that} chimpanzees do follow the point to a container \citep[see][p.\ 6]{Moll:2007gu}.

Hare & Tomasello 2004

‘to understand pointing, the subject needs to understand more than the individual goal-directed behaviour. She needs to understand that by pointing towards a location, the other attempts to communicate to her where a desired object is located; that the other tries to inform her about something that is relevant for her’

\citep[p.\ 6]{Moll:2007gu}.

Moll & Tomasello 2007

Why don’t apes point comprehend pointing gestures?

What we've said is about comprehending pointing.
But our question was, Why don't apes point?
I think we can answer both questions, the one about production and comprehension together.
I've taken the detour via comprehension only because I it's easier to see the answer in the case of comprehension.
Here's what we already have about comprehending pointing gestures.
This explains why apes don't comprehend pointing gestures --- they don't know (2) or (3) or both.
But what can we say about why they don't point? Think about what would be involved in producing a pointing gesture.

Informative pointing

To comprehend:

  1. know that this person is pointing to location L;
  2. know that by so pointing she is attempting to communicate; and
  3. know that what she is attempting to communicate is that object X it at L.
Here's parallel view about production.

To produce:

  1. know how to point to location L;
  2. know that by pointing to location L you can communicate with this audience;
  3. know that what you can communicate is that object X is at L.
So why don't apes point?
Because they don't know (2) or (3) or both.

Why don’t 3-month-olds point?

Tomasello also asks this question.
‘the specific behavioral form — distinctive hand shape with extended index finger — actually emerges reliably in infants as young as 3 months of age (Hannan & Fogel, 1987). […] why do infants not learn to use the extended index finger for these social functions at 3 – 6 months of age, but only at 12 months of age?’ \citep[p.\ 716]{Tomasello:2007fi}
(Again Tomasello's answer involves shared intentionality: it's because they don't understand shared intentionality until around their first birthdays.)
We can answer this in the same way --- they don't understand communication.
This makes sense of why chimpanzees don't point --- they don't understand communicative intention.

Why don’t apes point?

(And why don’t they understand declarative pointing?)

Because they fail to ‘understand that by pointing towards a location, the other attempts to communicate to her where a desired object is located’ (Moll & Tomasello 2007)

Note that this is an explanation which doesn't mention shared intentionality.
That's deliberate; sometimes Tomasello and colleagues answer this question by appeal to shared intentionality; I wanted to consider a simpler answer first and postpone thinking about shared intentionality for as long as possible.
Compare \citep[p.\ 516]{Tomasello:2010dy}: ‘they do not understand communicative intentions’

But

  • What is it to understand this?
  • Do 12-month-old humans understand it?

But is this consistent with the findings that 12-month-old infants do point?
What is it to understand that by this pointing action another intends to communicate that?
\subsection{pointing vs linguistic communication}
‘the most fundamental aspects of language that make it such a uniquely powerful form of human cognition and communication---joint attention, reference via perspectives, reference to absent entities, cooperative motives to help and to share, and other embodiments of shared intentionality---are already present in the humble act of infant pointing.’ \citep[p.\ 719]{Tomasello:2007fi}
‘cooperative communication does not depend on language, […] language depends on it.’ \citep[p.\ 720]{Tomasello:2007fi}
‘Pointing may […] represent a key transition, both phylogenetically and ontogenetically, from nonlinguistic to linguistic forms of human communication.’ \citep[p.\ 720]{Tomasello:2007fi}

appendix

I want to say a tiny bit more on what is involved in understanding a pointing gesture.
Suppose that we are doing puzzle. Then if I point to a piece, I probably intend you to do something with it in the context of our activity.
By contrast, if we are tidying up, a point to the same object might mean something different.
So:
Comprehending pointing is not just a matter of locking onto the thing pointed to; it also involves some sensitivity to context \citep[see][]{Liebal:2010lr}.
This is nicely brought out in a study by Christina Liebel and others.
\subsection{Pointing: referent and context}

pointing: referent and context

Liebal et al 2009, figure 1

Liebal et al 2009, figure 2

18-month-olds can do this, but 14-month-olds can't. (Don't infer anything from null result.)

Liebal et al 2009, figure 3

Liebal et al 2009, figure 4

‘Already by age 14 months, then, infants interpret communication cooperatively, from a shared rather than an egocentric perspective’ \citep[p.\ 269]{Liebal:2010lr}.
‘The fact that infants rely on shared experience even to interpret others’ nonverbal pointing gestures suggests that this ability is not specific to language but rather reflects a more general social-cognitive, pragmatic understanding of human cooperative communication’ \citep[p.\ 270]{Liebal:2010lr}.