Press the right key for the next slide (or swipe left)

also ...

Press the left key to go backwards (or swipe right)

Press n to toggle whether notes are shown (no equivalent if you don't have a keyboard)

Press m or double tap to see a menu of slides

 

Permanence

Three requirements

  • segment objects
  • represent objects as persisting (‘permanence’)
  • track objects’ interactions
\textit{Object permanence}:

Object permanence:

the ability to know things about, or represent, objects you aren't currently perceiving.

Permanence is a matter of living in a world where things don't go out of existence when unperceived.
You may not be perceiving your keys now, but there is a fact of the matter about where they are and you know this. (If not where they are, then at least you know that there is a fact about where they are.)

‘young infants’ physical world, like adults’, includes both visible [perceived] and hidden objects’

(Wang et al 2004, p. 194)

Although segmentation and permanence are conceptually distinct, they are closely related because movement is a clue to segmentation and movement sometimes invovles occlusion.
This becomes evident if we think about one more principle of object perception, the principle of continuity.

principle of continuity---

an object traces exactly one connected path over space and time

\emph{Principle of continuity} An object traces exactly one connected path over space and time \citep[p.\ 113]{spelke:1995_spatiotemporal}.
We easily understand this principle by considering cases that accord with, and violate, it.
Here is motion in accord with it.

Spelke et al (1995, figure 1)

Here is one violation of continuity.
And here is another violation of continuity.
\citet{spelke:1995_spatiotemporal} tested sensitivity to the principle of continuity in 4-month-old infants.
The infants were habituated to one of two displays.

Spelke et al (1995, figure 2)

Now in the continuous event we should perceive one object whereas in the discontinous event we should perceive two objects.
But is this about segmentation or persistence?
Segmentation since it's about distinguishing one object from another; and persistence since it's about representing temporarily unperceived objects.
They were then shown one of two test stimuli.
The measure was the degree of dishabituation as measured by looking time.

Spelke et al (1995, figure 3)

What's beautiful about these results is that the two groups show opposite patterns of dishabituation.
Recall that the continuity principle could be violated in two ways.
We've just seen a `continuity violation'. Next I want to show you a solidity violation.
Further evidence that infants represent unperceived objects from around four months includes Baillargeon's famous drawbridge study.
These are the test events from Experiment 1 of Baillargeon et al's 1987 study.
\begin{center} \citealp{baillargeon:1987_object} figure 1 \end{center}

Baillargeon et al (1987, figure 1)

'The habituation event was exactly the same as the impossible event, except that the yellow box was absent.' (Baillargeon et al 1985, 200)
These are the results from Experiment 1 of Baillargeon et al's 1987 study.
\begin{center} \citealp{baillargeon:1987_object} figure 2 \end{center}

source: Baillargeon et al (1987, figure 2)

I'm presenting this experiment as showing that infants represent objects as persisting, and do so in accordance with the Principle of Continuity. However, the experiment is also about causal interactions between objects. After all, infants are demonstrating sensitivity to the fact that a solid object must stop the drawbridge from rotating all the way back.
Some have been critical of the methods used in this experiment. But not everything hangs on this experiment. Fortunately there are at least a hundred further experiments which provide evidence pointing in the same direction. Here we'll look at just one more experiment.
Here is another way of demonstrating object permanence.
This experiment will suggest, incidentally, that the principles we have seen---continuity, rigidity and the rest---don't fully explain how infants succeed in representing objects as persisting.
The subjects were 4 month old infants.
They were shown a large object disappearing inside a small conatiner, or behind a narrow screen.

Wang et al (2004, figure 1)

The experiment was very simple.
All the experimenters did was measure how long infants looked in at the two events.
Infants looked longer at the narrow-occulder event.

Wang et al (2004, figure 2)

There was also a control condition.
In the control condition, infants saw a small rather than a large object.

Control condition

Wang et al (2004, figure 1)

Here’s the experimental condition again for comparison.

Experimental condition

Wang et al (2004, figure 1)

And here's the control condition again.

Control condition

Wang et al (2004, figure 1)

As you can see, there was a difference in looking times only in the experimental condition.

Wang et al (2004, figure 2)

This experiment is interesting because it doesn't use habituation, as Baillargeon's earlier drawbridge experiment did.

methods

habituation vs violation-of-expectation

[*Spend some time on habituation vs violation-of-expectations]
How should we interpret these results?
Interpreting violation-of-expectation experiments:
‘evidence that infants look reliably longer at the unexpected than at the expected event is taken to indicate that they (1) possess the expectation under investigation; (2) detect the violation in the unexpected event; and (3) are surprised by this violation. The term surprise is used here simply as a short-hand descriptor, to denote a state of heightened attention or interest caused by an expectation violation.’
\citep[p.\ 168]{wang:2004_young}

‘evidence that infants look reliably longer at the unexpected than at the expected event is taken to indicate that they

‘(1) possess the expectation under investigation;

‘(2) detect the violation in the unexpected event; and

‘(3) are surprised by this violation.’

‘The term surprise is used here simply as a short-hand descriptor, to denote a state of heightened attention or interest caused by an expectation violation.’

(Wang et al 2004, p. 168)

Note that we are talking about expectations.
This raises two questions: How do we arrive at these expectations? and What is an expectation?
Spelke's claim is that we arrive at these expectations by inference from the Principles of Object Perception, including the principle of contintuity.
So what is an expectation?
On the simple view we are adopting for now, an expectation is just a belief.
The attraction of this simple view is it allows us to take literally the claim that we know the principles of object perception and arrive at expectations by a process of inference.
*todo*

‘To make sense of such results [i.e. the results from violation-of-expectation tasks], we … must assume that infants, like older learners, formulate … hypotheses about physical events and revise and elaborate these hypotheses in light of additional input.’

\citep[p.\ 329]{Aguiar:2002ob}

(Aguiar and Baillargeon 2002: 329).

So the abilities to segment objects and to represent them as persisting are conceptually distinct.
However it may be that knowledge of a single set of principles underlies both abilities.
This is one of Spelke's brilliant insights.
Where does this leave us?
We still want to know about the status of the principles of object perception.
But we now the question is more pressing.
Because the claim that these principles of object perception explain infants' (and adults', and other primates') performance is now harder to reject.
It's harder to reject because we have converging evidence for the psychological reality of the principles from both segmentation and permanence.
Before we go any further, let me say a little more about the third thing on our list, causal interactions ...

principles of object perception

{

segmentation

permanence

... (?)

As an aside I wanted to mention that object permanence is found in nonhuman animals including

Object permanence is found in nonhuman animals including

\begin{enumerate}
  • monkeys (Santos et al 2006)
    \item monkeys \citep{santos:2006_cotton-top}
  • lemurs (Deppe et al 2009)
    \item lemurs \citep{deppe:2009_object}
  • crows (Hoffmann et al 2011)
    \item crows \citep{hoffmann:2011_ontogeny}
  • dogs and wolves(Fiset et al 2013)
    \item dogs and wolves \citep{fiset:2013_object}
  • cats (Triana & Pasnak 1981)
    \item cats \citep{triana:1981_object}
  • chicks (Chiandetti et al 2011)
    \item chicks \citep{chiandetti:2011_chicks_op}
  • dolphins (Jaakkola et al 2010)
    \item dolphins \citep{jaakkola:2010_what}
  • ...
    • \item ...
\end{enumerate}
(Wolves matter because their performing similarly to dogs that show dogs' performance probably isn't a consequence of domestication, as \citet{fiset:2013_object} argue.)
Most of these animals have been tested using search as the measure, rather than looking times. (This will be important later.)
 
Note also that many of these studies contrast visible with invisible displacements, or talk about Piaget's stages of object permanence. For simplicity, that's not something I'm covering.
[Aside] Comparative research is hard.

‘The real difficulty is that there is no reward for the great majority of cats in retrieving an unmoving, silent, odor-free, covered-up object from which their attention has been distracted, and hence the cats will not show that they know where it is.’

(Triana & Pasnak 1981, p. 138)