Costantini et al, 2012
In adults, we got at a parallel question by tying their hands.
There’s a similar manipulation in infants involving sticky mittens ...
Needham et al, 2002 / https://news.vanderbilt.edu/files/sticky-mittens.jpg
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.
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}.
Sinigalia & Butterfill 2015, figure 1
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.’