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Motor Representation in Object Cognition

 

Motor Representation in Object Cognition

[email protected]

\emph{The CLSTX conjecture} Five-month-olds’ abilities to track occluded objects are not grounded on belief or knowledge: instead they are consequences of the operations of object indexes. \citep{Leslie:1998zk,Scholl:1999mi,Carey:2001ue,scholl:2007_objecta}.

The CLSTX conjecture:

Five-month-olds’ abilities to track briefly unperceived objects

are not grounded on belief or knowledge:

instead

they are consequences of the operations of

a system of object indexes.

Leslie et al (1989); Scholl and Leslie (1999); Carey and Xu (2001)

(‘CLSTX’ stands for Carey-Leslie-Scholl-Tremoulet-Xu \citep[see][]{Leslie:1998zk,Scholl:1999mi,Carey:2001ue,scholl:2007_objecta})
While I wouldn’t want to suggest that the evidence on siganture limits is decisive, I think it does motivate considering the hypothesis and its consequences. In what follows I will assume the hypothesis is true: infants’ abilities to track briefly occluded objects depend on a system of object indexes.
occlusionendarkening
violation-of-expectations

Charles & Rivera (2009)

How does help us with the puzzles?
Object indexes can survive occlusion ...
... but not the endarkening of a scence
But why do we get the opposite pattern with search measures?
So why do 5 month olds fail to manifest their ability to track briefly occluded objects by initiating searches for them after they have been fully occluded?
Because object indexes are independent of beliefs and do not by themselves support the initiation of action.
But we still have to explain this ...
Why do infants succeed in searching for momentarily endarkend objects? This finding seems to run directly against the CLSTX conjecture. After all, (1) object indexes do not survive endarkening; and (2) even if they did, they don’t enable you to initiate purposive actions. So the CLSTX conjecture provides two independent reasons to predict that 5-month-olds will **not** search for endarkened objects.
And yet they do. What does this mean?

Cardellicchio, Sinigaglia & Costantini, 2011 figure 1

Thinks about how adults represent objects. For adults, it is not just a matter of knowledge and object indexes. Objects are also represented motorically. But how an object is represented motorically depends on its affordances.
And representing an object motorically generally depends on its being one you could interact with.

Cardellicchio, Sinigaglia & Costantini, 2011 figure 2

[skip --- only included in case need for discussion]

Costantini et al, 2010 figure 1B

Importantly, putting a barrier between you and an object means that you can’t interact with it, and so the object is unlikely to be represented motorically.
And note that it doesn’t matter whether the barrier is an occluder; even a translucent barrier will prevent objects being represented motorically.

Costantini et al, 2010 figure 1B

[skip --- only included in case need for discussion]
survive occlusionsurvive endarkening
object index
motor representation✘ (barrier)

 

occlusionendarkening
violation-of-expectations
\emph{The CLSTX conjecture} Five-month-olds’ abilities to track occluded objects are not grounded on belief or knowledge: instead they are consequences of the operations of object indexes. \citep{Leslie:1998zk,Scholl:1999mi,Carey:2001ue,scholl:2007_objecta}.

The CLSTX conjecture:

Five-month-olds’ abilities to track briefly unperceived objects

are not grounded on belief or knowledge:

instead

they are consequences of the operations of

a system of object indexes.

Leslie et al (1989); Scholl and Leslie (1999); Carey and Xu (2001)

(‘CLSTX’ stands for Carey-Leslie-Scholl-Tremoulet-Xu \citep[see][]{Leslie:1998zk,Scholl:1999mi,Carey:2001ue,scholl:2007_objecta})

 

... and of a further, independent capacity to track physical objects which involves motor representations and processes.

This generates lots of predictions. For example, should be able to modulate object tracking of endarkened objects by interfering with, or boosting, motor cognition. But the same manipulations should not affect occlusion.

McCurry et al 2009, figure 1 (part)

Perfect way to deconfound barrier and occlusion: a screen you can’t see through but can reach through.
Irony: McCurry et al call their paper ‘beyond the search barrier’. But the whole point of an experiment like this should have been to deconfound occluders and barriers (one blocks vision, the other prevents action).

McCurry et al 2009, figure 1

Now consider an experiment with 5-month-olds using an occluder that is no barrier to ation. Instead the occluder is a fringed screen through which you can reach.
Here's the authors' description of their procedure. 'Once the ball came to rest at the right edge of the platform, the platform was pushed forward until the edge of the platform was directly in front of, and within easy reach of, the infant. In the second phase, the infant was allowed to search for 20 s. ' (McCurry, Wilcox, & Woods, 2009)
McCurry et al found that 5 month old infants reach towards the cloth screen more often when a cube goes in and a ball comes out than when a cube goes in and a cube comes out. (I.e. cube-ball vs cube-cube.)
Why? On the CLSTX conjecture, this makes no sense. As we saw, a signature limit of object indexes is their disregard for featural information. Further, object indexes don’t enable you to initate purposive actions. So the CLSTX conjecture provides two reasons for making the incorrect prediction that infants will not search longer in the cube-ball condition than in the ball-ball condition.
But if you think about it in terms of motor representations, it makes perfect sense. Here is an occluder that is no barrier for action, so no obstacle to representing the objects motorically. And of course motor processes care deeply about the shapes of things, so we should expect a difference between the ball and the cube.
McCurry et al designed the perfect experiment to show that the CLSTX conjecture is not the whole story, and that 5-month-olds can represent unperceived objects motorically. But I don’t want to make too much of this because I’m interpreting their findings post hoc. Unfortunately this is not at all how they interpret their work. Instead, they write that ‘when task demands are minimal (successful performance requires only a direct reach through the fringe) young infants search reliably for hidden objects.’ But I don’t think anyone who has carefully considered Shinskey and Munakata’s work could be convinced by this idea. It’s a shame they weren’t thinking in terms of the Crude Picture of the Mind, but, you know, tant pis.
[skip] What should we predict? Cloth screen does not prevent action,\footnote{ ‘In the first familiarization trial, infants were shown the fringed-screen and were encouraged to reach through the fringe. If necessary, the experimenter gently guided the infant’s hand through the fringed-screen. Once the infant placed his or her hand through the fringed-screen twice, the trial ended.’ } so reaching should be possible. Further, if motor representations are responsible for the effect, the fact that the experiment requires sensitivity to featural information should not be an issue. (Further, a version of this task using violation of expectations may fail because featural information is critical.) And although these are very far from the terms in which they interpret their findings, this is exactly what McCurry et al 2009 found.

McCurry et al 2009, figure 2

\emph{The CLSTX conjecture} Five-month-olds’ abilities to track occluded objects are not grounded on belief or knowledge: instead they are consequences of the operations of object indexes. \citep{Leslie:1998zk,Scholl:1999mi,Carey:2001ue,scholl:2007_objecta}.

The CLSTX conjecture:

Five-month-olds’ abilities to track briefly unperceived objects

are not grounded on belief or knowledge:

instead

they are consequences of the operations of

a system of object indexes.

Leslie et al (1989); Scholl and Leslie (1999); Carey and Xu (2001)

(‘CLSTX’ stands for Carey-Leslie-Scholl-Tremoulet-Xu \citep[see][]{Leslie:1998zk,Scholl:1999mi,Carey:2001ue,scholl:2007_objecta})

 

... and of a further, independent capacity to track physical objects which involves motor representations and processes.

This generates lots of predictions. For example, should be able to modulate object tracking of endarkened objects by interfering with, or boosting, motor cognition. But the same manipulations should not affect occlusion.