Categorical Perception and Knowledge

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Harnad offers a hypothesis which might seem natural to accept at this point.

How is categorical perception involved in the emergence of the knowledge of colours of things?

Categorical perception provides ‘the building blocks—the elementary units—for higher-order categories’

\citep[p.\ 3]{Harnad:1987ej}.

Harnad, 1987 p. 3

Incidentally, Spelke also uses the building blocks metaphor.

But of course Spelke is talking about core knowledge rather than categorical perception. (I think the two might be related, but I suspect she would strongly disagree.)

‘The building blocks of all our complex representations are the representations that are constructed from individual core knowledge systems.’

\citep[p.\ 307]{Spelke:2003fc}

Spelke, 2003: 307

But is it true?

The first problem is to understand the ‘building blocks’ metaphor.

View 1 : Having categorical perception of colour (or X) amounts to having colour (or X) concepts.

‘The module … automatically provides a conceptual identification of its input for central thought … in exactly the right format for inferential processes’

(Leslie 1988: 193-4)

We'll say something about what modules are later---for now, just be aware that categorical perception counts as a modular process.

Is this right?

Here's a first attempt to understand the ‘building blocks’ metaphor. Let's suppose that categorical perception of colour amounts to having colour concepts. This way of thinking concords with Leslie's view about modular cognition.

The toy is put away so that the subjects couldn't see it.

Which one of these is like the toy I just put away?

Kowalski and Zimiles, 2006 Experiment 2

It can't be right that having categorical perception of colour (or X) amounts to having colour (or X) concepts. We know this can't be right because there is a gap of two or more years between categorical perception of colour and possession of colour concepts. For consider what is involved in having a colour concept. It is not just responding differently to red things than to green things (say). It also requires

Acquiring colour concepts depends on acquiring colour words..

\citep{Kowalski:2006hk}.

But for now Kowalski and Zimiles are important because they show that having categorical perception of colour is not the same thing as having colour concepts.

‘the course of acquisition for color is protracted and errorful’

\citep{Sandhofer:2006qo}

Sandhofer and Thom, 2006

NO

View 1 : Having categorical perception of colour (or X) amounts to having colour (or X) concepts.

‘The module … automatically provides a conceptual identification of its input for central thought … in exactly the right format for inferential processes’

(Leslie 1988: 193-4)

Is this right?

So the first view can't be right. It can't be right that having categorical perception of colour (or X) amounts to having colour (or X) concepts. And the same applies in other cases of categorical perception as well. (Of course a defender of the view that categorical perception is or entails concept possession might insist that subjects have concepts but cannot use them, at least not in the sort of task I have just described. This is possible, of course, but it seems to be a desperate defence.) How else might we understand the ‘building blocks’ metaphor?

View 2 : redescription

‘the earliest conceptual functioning consists of a redescription of perceptual structure’

(Mandler 1992)

One worry here is that we've replaced one metaphor with another, ‘redescription’ for ‘building block’. But let's put this aside for a moment in order to reflect on why Mandler is wrong.

Is this right?

Consider Mandler's claim that ‘the earliest conceptual functioning consists of a redescription of perceptual structure’ (Mandler 1992)

The boundaries of adults' perceptual categories do not match the boundaries of infant and toddler perceptual categories. How do we know? First note that the extensions of colour terms vary between languages.

The extensions of colour terms vary between languages.

(E.g. Russian colour terms include ‘goluboy’ (for lighter blues) and ‘siniy’ (for darker blues).)

Indeed, the extensions of colour terms vary quite radically between languages. Ongoing research concerns whether there is any kind of universal prinicple behind the pattern.

English

Roberson & Hanley 2010, Figure 1c

Berinmo

Roberson & Hanley 2010, Figure 1b

So the extensions of colour terms varies between langauges.

Why is this relevant to the relation between infant and adult categorical perception?

The extensions of colour terms vary between languages.

(E.g. Russian colour terms include ‘goluboy’ (for lighter blues) and ‘siniy’ (for darker blues).)

Because the boundaries of adults' (but not infants') perceptual categories are influenced by the extensions of their culturally variable colour terms.

For evidence that adults' perceptual colour categories are influenced by their culturally variable knowledge of colour words, see \citet{Kay:2006ly}, \citet{Roberson:2007wg}, and \citet{Winawer:2007im};

In monolingual adults, the perceptual categories match the extensions of the colour terms in their language.

Roberson and Hanley, 2007; Winawer et al, 2007

This is an amazing finding about the power of words. Learning to use words for colours influences how we categorise them in categorical perception them.

Colour words shape adults’ categorical perception \citep{Roberson:2007wg,Winawer:2007im}.

We'll see more on this later.

But, as you'd expect, infants’ and toddlers’ perceptual categories are not influenced by the extensions of colour terms.

For evidence that toddlers who know some colour words show no influence of language on categorical perception of colours, see \citet{Franklin:2005hp}.

Infants’ and toddlers’ perceptual categories are not influenced by the extensions of colour terms.

Franklin et al, 2005

Therefore:

Infants’ perceptual categories do not match adults’ concepts.

no?

View 2 : redescription

‘the earliest conceptual functioning consists of a redescription of perceptual structure’

(Mandler 1992)

Is this right?

So the second view probably isn't right either. For whatever redescription amounts to, it should surely involve there being some kind of match between the perceptual categories and the concepts. And, on the face of, it there is no match at all.

So what are we to make of the ‘building blocks’ idea? It may be that we have to reject the building blocks idea altogether. For infant categorical perception of colour seems only very distantly related to adult uses of colour concepts. Does this mean that categorical perception plays no role at all in explaining the emergence of knowledge about colours? No, we haven't shown that. Only that categorical perception alone is not enough; and also that it is hard to understand exactly how categorical perception plays a role in the emergence of knowledge.

Categorical perception provides ‘the building blocks—the elementary units—for higher-order categories’

\citep[p.\ 3]{Harnad:1987ej}.

Harnad 1987, p. 3

The role of some early-developing abilities in explaining the later acquisition of conceptual understanding does not involve direct representational connections; rather the early developing abilities influence attention and inform behaviour, and these influences facilitate development.

development as rediscovery

What is missing from the building blocks idea is adequate recognition that social interaction is important for the emergence of knowledge.

The challenge, of course, is to say *how* social interaction enables humans to come to know things.

Vygotskian Intelligence Hypothesis:

In emphasising rediscovery I want to identify a major role for social interaction while also recognising the importance of the early developing representations of colours, objects and causes.

The idea is, roughly, that coming to have knowledge involves rediscovering information that is already represented.

How might the idea of development as rediscovery apply in the case of knowledge of colour?

In acquiring a colour concept or word you need to:

identify the dimension (colour not shape, size, or ...)
locate the boundaries

On locating the boundaries, I think having colour words might be helpful as a way of marking a category before you know where its boundaries are. That is, the word allows you to re-identify a category without knowing where it begins or ends.

Given differences between the boundaries of pre-verbal infants' perceptual categories and the extensions of colour words, it seems unlikely that categorical perception could help here. (Although it is possible in principle that, due to abstract features common to all languages' systems of colour words, categorical perception might help; see Kay and ?*.)

It's with this first problem that I think categorical perception helps with. I suggest that categorical perception enables you to lock onto the relevant dimension.

How? Categorical perception alters your experience so that there's a correspondence between (i) changes on the relevant dimension, and (ii) changes in one phenomenal aspect of your experience. This correspondence helps you, eventually, to lock onto the relevant dimension and so to acquire concepts and words. Let me illustrate.

One effect of categorical perception is phenomenological. Consider the (a) difference between an experience of the first blue and the second blue; and (b) the difference between an experience of the second blue and the green. Phenomenally, the second pair of experiences is more different than the first. There is some kind of phenomenological marker of categorical colour properties. To put it colourfully, there is something that it is like for you to experience blue, and something else that it is like for you to experience green. So, to return to the two problems, this is why I think categorical perception might be important for identifying the dimension.

The question for this lecture was, how do we come to know things about colour. The answer, I think, is this. We have categorical perception of colour from early in infancy, certainly from around four months of age. Having categorical perception is not by itself sufficient for having colour concepts. But it does play an important role, because it means that there is a correspondence between (i) changes on the relevant dimension, and (ii) changes in one phenomenal aspect of our experience. I conjecture that this helps us to identify the relevant dimension, colour not shape or size, in acquiring colour words and concepts. But by itself this is not enough. As we've seen, acquiring colour concepts also depends on having some colour words. I speculate that this is because words function as a tool for marking categories prior to knowing where they start and end. The word allows you to re-identify a category without knowing where it begins or ends.

So this is my picture. Acquiring knowledge of colour depends on an interaction between categorical perception, something developmentally quite primitive, and social interaction, in particular the negotiation of words for colour categories.

[SKIP --- just left here as placeholder] [Also note that there’s a simpler walkthrough of the core idea here at the start of lecture_08 Would include that here but TIME!]

[Diagram: years bewteen early capacities (core knowlegde) and knowledge proper.] Relate this to the gap between Core Knowledge and Knowledge Knowledge.

To conclude, we've seen that although infants enjoy categorical perception of colour from four months or earlier, this doesn't straightforwardly explain how they come to know about the colours of things. In particular, having categorical perception does not entail having a concept. Nor does having a concept seem to be a matter of somehow redescribing or latching on to what is catgeorically perceived. On the other hand, having colour words and being able to use them accurately does seeem to matter for the acquisition of knowledge of colour. So this is one example where having verbal labels for things may help with acquiring concepts of them.

conclusion

building blocks: no; rediscovery: maybe

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Categorical Perception and Knowledge

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