Sound changes versus sound changes

[Vidhyanath Rao]

> [Steve Long:]

> The other factor is HOW "DISSIMILAR" those changes are, in the sense that you
> used similar above, in "little or no similarity."  We're not talking about
> "unexpected" or uncommon shifts here but rather shifts that make the words
> sound significantly different.  In other words, a fricative to a labial
> versus a fricative to another fricative.  An ordinary listener might have a
> better chance of finding a similarity in the latter than the former.

But sound changes don't seem to work that way. Labov, in his monograph
about sound changes, looked at various examples of changes in progress
and came to the conclusion that changes of place are more complex than
changes of effort and such things at metathesis can remain partial,
limited by semantics etc. So p>f may be a smaller change than f > th.