Mental sharpness and bilingualism

[William J Poser]

The finding reported in the article that Jess cites that
childhood bi- and multi-lingualism is associated with better
cognition among elders parallels previous findings of similar
advantages among younger adults. I suspect that there is some
cognitive advantage to multilingualism, but it is difficult to
be really sure because it is virtually impossible to control
for all of the relevant variables in such studies. The only
way to do a perfect experiment would be to randomly select
the children to be raised monolingual and the children to be
raised multilingual prior to birth from a population in which
they could be expected to be brought up in similar ways.
Unfortunately (from a strictly scientific point of view),
this is not possible. Such studies are therefore always of
populations where one can never be 100% certain that some other
relevant factor does not differentiate the monolingual and
multilingual subjects.

So, yes, I think that one can use such studies as support for
the virtue of speaking more than one language, but I wouldn't
want to push it too hard because of the methodological problem.
Note also that there is an earlier literature that claims the
opposite, that is, that bilingualism is damaging. Those studies
are subject to the same methodological limitation (as well as
others - most of them are really bad) so if nothing else the
more recent positive studies can be taken as refuting the
earlier negative ones.

Bill