Creating indices on foreign keys

I think PostgreSQL does not create indexes on foreign keys of a table,
and I have to do so explicitly. That means, wherever I am using master-
detail table, I have to create explicit indexes on the foreign key in
the detail table. Am I wrong?

Refering the discussion here, I assume I am correct:

http://groups.google.co.in/group/pgsql.general/browse_thread/thread/516db5b5f36c82d0

thanks
Sanjay