Categorical perception

[Sherman Wilcox]

This isn't really about categorical perception, but I'll use the same
thread...

The type of data that Liberman & Mattingly used to argue that "speech is
special" can also be found in fingerspelling. That is, they said:

"... the relationship between gesture and signal is not straightforward
... the movements for gestures implied by a single [phonetic] symbol are
typically not simultaneous, and the movements implied for successive
[phonetic] symbols often overlap extensively. This coarticulation means
that the changing shape of the vocal tract, and hence the resulting
signal, is influenced by several gestures at the same time. Thus, the
relation between gesture and signal, though certainly systematic, is
systematic in a way that is peculiar to speech." (L &M, "The motor theory
of speech perception revisited," Cognition 21, 1985).

>>From this, L &M argued that this coded relationship between gesture and
speech requires a special module for phonetic perception, beyond what is
required for general acoustic perception.

But the same "coded" relationship exists between the articulatory
gestures that make up fingerspelled letters and the resulting optical
signal: (1) movements for gestures implied by a single [fingerspelled]
symbol are typically not simultaneous, and (2) movements implied by
successive [fingerspelled] symbols overlap extensively. Coarticulation is
very much present in fingerspelling. It is therefore equally true of
fingerspelling to say that the changing shape of the [fingerspelling
tract? OK, the hand], and hence the resulting [optical] signal, is
influenced by several gestures at the same time, and thus that the
relation between gesture and signal is systematic in a way that is
peculiar to fingerspelling.

Does this then lead us to conclude that a special module for
fingerspelling perception is required?

-- Sherman Wilcox