The origin of pointing: Evidence for the touch hypothesis

We are very grateful for Adolf Heschl’s reply, although we remain convinced that the touch hypothesis is the best explanation of our results. To remind the reader: in our paper we report three findings. First, that when pointing gestures are produced, the best predictor of what they refer to is not the angle of the pointing finger, which we called the ‘arrow-line’, but rather a line connecting the eye and finger-tip – the line on which you find the object that it looks to the pointer as if she is aiming to touch. Second, that when pointing at objects at odd angles, people rotate their wrists as they would were they trying to touch that object. And finally, we showed that infants are more likely to interpret pointing gestures to refer to the object that it looks as though a pointing figure is trying to touch, than an object that is found along the ‘arrow’ of the pointing finger. We argued that our results are be explained by the hypothesis that pointing gestures emerge from touch-exploration in infancy. Heschl argues that a better way to explain these results is on the basis of reaching – as Vygotsy and others have supposed may be the origin of pointing gestures.

First let us consider Heschl’s proposal for testing the reaching hypothesis in the context of our results.

Heschl proposes that an ‘arm line’ – a vector drawn along the arm from shoulder to wrist in a pointing gesture – will provide a good indicator of what a person is reaching for. If pointing originates in reach, this line should be as good or better a predictor of what a gesture refers to as our ‘touch line’. We agree. To test whether the ‘arm line’ is a better predictor than the ‘touch line’, we took a random sample of 40 shots of participants pointing from our data (5 slides from 2 subjects in each age group). We constructed an ‘arm line’, following Heschl’s proposal, along with the original ‘touch-line’ extending from eye through finger-tip. We measured the angular distance of each line from the target (see sample image here), and tested which line is closer to the target. Even with this small sample, we found that the touch line is significantly closer to the object referred to than the arm-line (in 32 of 40 observations the touch-line was closer; the touch-line average distance was 6.2°, the arm-line 12.9°; one-sample t-test: N=8, t=4.112, p<0.001; data available: https://osf.io/ucj69/). On Heschl’s account, this test thereby provides further support for the touch hypothesis, and against the reaching hypothesis (see illustration here: https://osf.io/w2k8s/).

Heschl is concerned that there is not enough evidence to regard touch exploration as prevalent enough in early infancy to act as a precursor for pointing – again preferring the reaching hypothesis. However, as we discussed in our paper, index-finger touch exploration is highly prevalent in the months leading up to the emergence of pointing (1) – more prevalent than reaching (the relative frequency of reaching and index-finger extension (touch exploration) can be viewed here: https://osf.io/ct6fy/; for similar results see (2)). Heschl is concerned that the effects we found are most prominent in the youngest age groups, and decrease with age. But, our hypothesis is about the ontogenetic origin of pointing – so the fact that these effects are greatest in the youngest age groups supports our position.

Regarding our interpretation study, Heschl proposes that the youngest age groups (18mths and 3yrs) might simply not yet understand pointing gestures. This is not plausible. First, it is well established that infants understand pointing gestures by 12-14 months (3, 4, 5). Second, participants in the youngest age groups systematically preferred the ‘touch’ interpretation to the ‘arrow’ interpretation of these gestures. If these groups had no particular interpretation of pointing gestures, they should have made choices at chance, rather than systematically preferring the ‘touch’ interpretation. Third, we ran a control condition, reported in our paper, where infants had to follow unambiguous points, and participants who failed this condition were excluded.

Some captive great apes have indeed learned to point, but only as imperative gestures (“gimme the coke”) as opposed to informative gestures (“look! A coke!”). Human children also produce such gestures – but these gestures differ systematically from informative pointing gestures. In human infants, imperative gestures are characterized by an open hand (in a ‘grabbing’ shape), and feature significantly less vocalization and joint attention than ‘informative pointing’ (with the distinctive index-finger extension) (6). The remarkable thing about informative pointing is that these gestures are produced solely with the goal of ‘telling’ the viewer something – getting someone to see something, or discover something. This is why informative pointing is implicated so strongly in the origin of language. While imperative gestures in human infants may well originate in reaching, and have a common ontogenesis as these gestures in apes, we think that the uniquely human informative pointing gestures have a distinct origin – in touch.

1. E. Bates, B. Benigni, I. Bretherton, L. Camaioni, & V. Voltera. Cognition and com- munication from nine to thirteen months: Correlational findings. In E. Bates (Ed.), The emergence of symbols: Cognition and communication in infancy (pp. 69–140). New York: Academic Press (1979).
2. N. Masataka, From Index-Finger Extension to Index-Finger Pointing: Ontogenesis of Pointing in Preverbal Infants. In Kita, S. (ed.) Pointing: Where Language, Culture and Cognition Meet. Lawrence Erlbaum Associates (2003).
3. T. Behne, M. Carpenter, & M. Tomasello, One-year-olds comprehend the communicative intentions behind getures in a hiding game. Developmental Science, 8(6), 492-499. Doi: 10.1111/j.1467-7687.2005.00440.x (2005).
4. T. Behne, U. Liszkowski, M. Carpenter, & M. Tomasello, M. Twelve-month-olds' comprehension and production of pointing. British Journal of Developmental Psychology, 30, 359-375. Doi: 10.1111/j.2044-835X.2011.02043.x (2012).
5. M. Tomasello, M. Carpenter and U. Liszkowski, A New Look at Infant Pointing, Child Development, Volume 78, Number 3, Pages 705 – 72 (2007).
6. H. Cochet, J. Vauclair, Pointing gestures produced by toddlers from 15 to 30 months: Different functions, hand shapes, and laterality patterns. Infant Behav. Dev. 33, 431–441 (2010).