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Performing vs Understanding Actions in Infancy

Infants use the teleological stance to identify goals.

But does this involve reasoning or motor processes?

Costantini et al, 2012

In adults, we got at a parallel question by tieing their hands. There’s a similar manipulation in infants involving sticky mittens ...

Needham et al, 2002 /

Needham et al, 2002 showed that putting ‘sticky mittens’ on 3-month-old infants (for 10-14 play sessions of 10 minutes each) resulted in their spending more time visually and manually exporing novel objects.

Sommerville, Woodward and Needham, 2005

Play wearing mittens then observe action.


Observe action then play wearing mittens then.

In this study, I think infants wore the mittens for just 200 seconds (so the play sessions were much shorter than in Needhman et al, 2002).
The observation was based on this study, which we saw earlier

Woodward et al 2001, figure 1

Sommerville, Woodward and Needham, 2005 figure 3

The results show that infants who played wearing the mittens first were more attentive to the goal.
From at least three months of age, some of infants’ abilities to identify the goals of actions they observe are linked to their abilities to perform actions \citep{woodward:2009_infants}.
But one potential objection to this study concerns observation vs performance. The infants who played wearing sticky mittens first had spent longer observing actions by the time it came to the violation of expectations trial. Could it be observation of action (including one’s own) rather than performance that matters?
In adults, tying the hands impairs proactive gaze \citep{ambrosini:2012_tie}; in infants, boosting grasping with ‘sticky mittens’ facilitates proactive gaze (\citealp{sommerville:2005_action}; see also \citealp{sommerville:2008_experience}, \citealp{ambrosini:2013_looking}).

Sommerville et al 2008, figure 1

To address this issue, \citet{sommerville:2008_experience} did a study in which one group had observation while the other group had performance. The participants were 10-month-old infants this time.
The materials were a bit different: so that training vs observation could be as similar as possible with respect to the causal structure exposed, there was a hook to get an object.

Sommerville et al 2008, figure 2

The results show that infants with the training paid attention to the distal goal (choice of toy) whereas those without paid attention to the choice of cane.

Ambrosini et al, 2013 figure 1 (part)

Further support for a link between action performance and goal ascription comes from a developmental study by Ambrosini et al which studied whether proactive gaze in infants is influenced by pre-shaping of the hand, and, in particular, whether it is influenced by precision grips.

Ambrosini et al, 2013 figure 1 (part)

Ambrosini et al, 2013 figure 1 (part)

By using no shaping (a fist), Ambrosini et al could treat sensitivity to whole-hand grasp and precision grip separately.

Ambrosini et al, 2013 figure 3

‘infants’ ability to perform specific grasping actions with fewer fingers directly predicted the degree with which they took advantage of the availability of corresponding pre-shape motor information in shifting their gaze towards the goal of others’ actions’ \citep[p.~6]{ambrosini:2013_looking}.


In infants and adults,
abilities to perform actions enable identifying goals when observing them.

Why is this true?

The Motor Theory of Goal Ascription:

goal ascription is acting in reverse

The idea is that we could solve the problem--the problem of matching optimisation in planning actions with optimisation in predicting them--by supposing that a single set of mechanisms is used twice, once in planning action and once again in observing them.
What does this require?

-- in action observation, possible outcomes of observed actions are represented

-- these representations trigger planning as if performing actions directed to the outcomes

-- such planning generates predictions

predictions about joint displacements and their sensory conseuqences

-- a triggering representation is weakened if its predictions fail

The proposal is not specific to the idea of motor representations and processes, although there is good evidence for it (which I won't cover here because we're in Milan!)

Sinigalia & Butterfill 2015, figure 1


In infants and adults,
abilities to perform actions enable identifying goals when observing them.

Why is this true?
In suggesting that it’s because of the Motor Theory, I’m going beyond anything Sommerville et al would endorse although moving in a direction they cautiously indicate.
I’m also contradicting how most people think of the relation between the Teleological Stance and the Motor Theory. Most theorists think of these as alternatives. E.g. \citep{Csibra:2007hm} contrast what can be explained with Teleological Stance and Motor Theory (they claim Teleological Stance is required for novel situations in which Motor Theory should fail; this is probably in part right, although success in the face of novelty could be driven by associations.) See also \citet[p.~204]{gredeback:2010_infantsa}: ‘We suggest that anticipation of action goals is mediated by a direct matching process (Flanagan & Johansson, 2003) whereas retrospective evaluations of rationality are dependent on more abstract well-formedness criteria as described by the teleological stance (Gergely & Csibra, 2003).’ (NB: their argument is not good: they claim that because infants who have little or no experience of feeding themselves can show suprise (pupil dilation) in response to nonrational self-feeding actions, they are using the Teleological Stance here. But it might be motoric; or it might be association (cf the ‘telephone to ear’ study).)

The Teleological Stance

... provides a correct computational description of (some or all) infant (and adult) goal ascription.

But which processes and representations underpin it?

Csibra & Gergeley’s hypothesis: ordinary inference and beliefs

The Motor Theory: motor representations and processes


Manipulating abilities to perform actions changes abilities to identify goals.


  1. Proactive gaze indicates fast goal ascription.
  2. The Teleological Stance provides a computational description of the goal ascription underpinning adults’ proactive gaze
  3. Proactive gaze depends on motor processes and representations: the Motor Theory provides an account of the representations and algorithms.


  1. Proactive gaze (from ~12 months) and violation-of-expectations (from ~3 months) indicate goal ascription.
  2. The Teleological Stance ...
  3. Two conjectures about algorithms and representations ...
The question was, Is there any evidence? ... Yes, we found evidence.

caveat: there’s probably more

There’s probably more than the Motor Theory to goal ascription (in infants, and adults).

Melzer et al, 2012 figure 1

\citep{melzer:2012_production}: ‘The infant was given a cube (occupation object) in either his/her left or right hand. Subsequently,a second toy (target object) was held either (a) in front of the empty hand to elicit an ipsilateral reaction (ipsilateral presentation) or (b) in front of the occupied hand to elicit a contralateral reaction (contralateral presentation).’

Melzer et al, 2012 figure 3

Infants become good at contralateral grasping between six and twelve months.

Melzer et al, 2012 figure 2

And here is an anticipatory looking task ...

Melzer et al, 2012 figure 4 (part)

How did the infants do? The data in figure indicate that 12-month-olds showed quite good, adult like anticipation of contralateral actions, whereas 6-month-olds were arriving at the target object behind the hand.
This suggests a link between performance and goal ascription, once more. (p. 577: ‘At 12 months, most infants were able to anticipate the goal of contralateral movements, whereas at 6 months, infants showed mainly reactive eye movements.’)
Further, p. 577: ‘Production and perception of contralateral reaching movements were correlated at 12 months of age. The more sophisticated 12-month-olds’ reaching production was, the better they anticipated other people’s contralateral movements.’
But the result that that \citet{melzer:2012_production} focus on is this: p. 577: ‘perception and production were not yet correlated at 6 months. The lack of a significant correlation was neither due to a larger variance in the younger infant group nor to the influence of a bias in our sample. Accordingly, our findings suggest that a link between production and perception of contralateral arm movements, and possibly therefore a common representation, develops in the second half of the first year of life.’