Reply to Bates' second note

[Steve Pinker]

In her second note, Bates writes as if the argument for "unique
qualitative mechanisms" was based entirely on the existence of a
U-shaped learning curve.  This reduction has the virtue of simplicity,
but it bears little resemblance to the actual arguments in the
literature, which work from a range of linguistic, psycholinguistic,
and developmental evidence. In our paper we discuss a variety of
developmental data independent of U-hood that bear on the question of
what kinds of mental mechanisms are involved (OLC, pp.139-145). We
also examine the qualitative differences between the irregular and
regular past-tense systems in some detail (pp.108-125). Of course the
issue is still open, but we doubt that the debate is ultimately going
to turn on slogan-sized chunks of assertion.

Aiming for another reduction, Bates asks, "Does the U-shaped function,
then, mean nothing more to P&P than the claim that errors come and
go?" What the U-shaped function means to us is "a function that is
shaped like a U".  You don't get a function shaped like a U merely if
"errors come and go". You also need some correct performance around
the time when errors come.  Otherwise the function (percentage error
vs. time) could be monotonically decreasing, not U-shaped. The
evidence that Bates first cited against the U-shaped curve was based
on a study that had nothing to do with the matter; then comes the
terminological dispute.

At this point, we'd like to sign off on the round robin.  We welcome
further inquiries, comments, and reprint requests at our own
addresses.

Alan Prince: prince at cogito.mit.edu
Steven Pinker: steve at psyche.mit.edu