Flanagan and Johansson, 2003 figure 1 (part)
To explain this I have to step back and show you something interesting about
adults when they perform, and when they observe actions.
Performing actions (e.g. stacking blocks): you don't look at your hand but at
the block it will pick up, or, when holding a block, at the location where it will place a block.
That is, in acting the eyes move just ahead of the action.
Kanakogi and Itakura, 2011 figure 1
‘Positive relative times of the arrival of gaze at the goal area indicate that gaze precedes the agent’s arrival (predictive);
negative values indicate gaze arrival after agent arrival (non-predictive). Each age group is n = 12.
Error bars are s.e.m.’
GH : grasping hand; BH : back of hand; MC : mechanical claw
Kanakogi and Itakura, 2011 figure 5 (part)
Kanakogi & Itakuar, 2011 show that abilities to grasp objects are correlated with
abilities to track the goal of a grasping action (as measured by proactive gaze).
x-axis is alpha, grasping angle. ‘An α angle value from 90 to 180° indicates that the infant
is engaged in a one-handed grasping action.’
‘The angle α is an index of the development of the onehanded grasping action and was
calculated by measuring the angle of a straight line de ned by the infant’s two hands (the
apex of the junction of the thumb and index nger) when crossed by an imaginary line
projecting frontally from the infant (Fig. 2b). If infants grasped for the objects with their
le hand, we reversed the red rightangled triangle from one side to the other side and
calculated the angle α in the same way. e angle α value of 90° corresponded to a perfect
alignment of the hands in a twohanded reach. erefore, the angle α value deviates from 90°
towards 180°, and bigger angle α value indicates more mature onehanded grasping. If the
angle α was over 90°, the infant was considered to be engaged in a onehanded grasping
action.’
Ambrosini et al, 2013 figure 1 (part)
Further support for a link between action performance and goal tracking
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}.
Kanakogi and Itakura, 2011 figure 1C (part)
Further, changing from a bodily action to the operation of a mechanical claw
(say) undermines the goal tracking effect.
So Kanakogi & Itakuar, 2011 make two points:
(i) goal-tracking depends on action capabilities; and
(ii) only works for events involving biomechanically similar affectors
Kanakogi and Itakura, 2011 figure 5
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
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.
... or IMPAIR INDIRECTLY ...
Bruderer et al, 2015 figures 1, 4
Experiment 1 : shows that 6-month-old infants can distinguish a phonetic contrast
they have never heard before (one that occurs in Hindi but not their linguistic
environments.) (The contrast used was the Hindi dental /d/̪ versus retroflex /ɖ/
distinction.)
These graphs show a difference in mean looking time between cases in which phonemes
are alternated and cases in which they are not. (Iff infants distinguish, they should
find the alternating phonemes more interesting.)
Experiment 2: but not when they have a tongue-controlling dummy in their mouths
Experiment 3: but yes when they have a dummy which leaves the tongue free.