Tree or wave?

[ECOLING at aol.com]

In a message dated 1/26/2000 10:55:35 PM, kurisuto at unagi.cis.upenn.edu writes:

>...Ringe, Warnow, and
>Taylor made use of this algorithm to compute the family tree for
>Indo-European.  There is certainly some noise in the data, and there are a
>few problematic areas (notably, the placement of Germanic and of
>Albanian), but on the whole, the same tree structure come up run after
>run.

>If it were the case that the proper model of the relations between the
>IE
>languages were really a fully general wave model, then this isn't the
>expected result; what you'd get in that case would be wildly different
>trees with every run of the algorithm, with very poor scores each time
>for
>how closely the tree comes to a perfect phylogeny.  This is in fact what
>happened when the team tried to compute a phylogeny of the West Germanic
>languages: the languages developed in close contact and shared innovations
>in ways which can't be captured in a tree.  But it's not what you get with
>the IE family in general, and this is very unlikely to be an accident.

Isn't the direction of this difference
(IE representable using tree model,
\vs. Germanic using wave model)
a predictable consequence merely of the difference in time depths,
that intermediates tend to have vanished more with greater
time depths?
If so, does it not have little or no empirical content of interest
to linguists?

***

>As a matter of scientific economy, we should always choose the most
>restrictive theory that the data will allow.  Tree representations are
>much more restrictive than wave representations; so if the data will allow
>us to claim that all language relations are properly represented in this
>more restrictive model, that's the claim we should make.  The _empirical_
>question is whether the IE languages will allow a tree representation.

As a *tentative hypothesis*, yes, because that may yield further progress.

But as a result or conclusion to be reported to non-specialists,
I believe the policy proposed above is a quite pernicious policy.
We should rather be conservative and report what we actually have evidence
for, that is the weakest hypothesis that is sufficient to account for the
data,
not anything unnecessarily stronger than that.

Occam's razor cannot decide empirical fact.
It can only point to a dangerous hyperelaboration of complex hypotheses
to account for some phenomena for which the true explanation may be
much simpler and quite different.

Lloyd Anderson
Ecological Linguistics