After
the mirror neurons saga, the neuromania/neurophobia affair and the dyslexia debate, another topic is
worthy of attention and will fascinate the readers: bilingualism and
its supposed cognitive benefits!
The
beginning was a meta-analysis of the published studies from
conference abstracts, showing a publication bias towards a bilingual
advantage compared to a disadvantage or no effect of bilingualism.
Then,
a couple of weeks ago Psychological
Science
published two Commentaries: a reply by Bialystok et al. and a
counter-response by de Bruin et al.
I've
selected some passages from these two commentaries, putting them
together as in a direct dispute.
I.
The Beginning
Cognitive
Advantage in Bilingualism: An Example of Publication Bias?
de
Bruin A, Treccani B, Della Sala S
Psychological
Science OnlineFirst, published on December 4, 2014 as
doi:10.1177/0956797614557866
Main
statements:
We
analyzed conference abstracts presented between 1999 and 2012 on the
topic of bilingualism and executive control. Conference abstracts
were classified on the basis of their outcome. We observed an effect
of result type on publication: Studies were published relatively
often (68%) if the data demonstrated a bilingual advantage. In
contrast, only 29% of the studies that showed no effect of
bilingualism or even a bilingual disadvantage were published.
This
difference in publication percentage based on the outcomes of the
study could be the result of a bias during several steps of the
publication process: Authors, reviewers, and editors can decide to
submit or accept only studies that showed positive results.
While
we agree that bilingualism should be conceived, a priori, as a
positive and desirable achievement, we are also convinced that
educational and political debates addressing the relevance of
bilingualism should not be promoted by ignoring null or negative
results. Instead of selecting exclusively those tasks and results
that support current theories, investigators should attempt to
include all conducted tasks and reported findings. On the other hand,
reviewers and editors should be more open to studies that challenge
the existing theories, especially when these are not yet fully
established.
II.
The Reply
Publication
Bias and the Validity of Evidence: What’s the Connection?
Bialystok
E , Kroll JF, Green DW, MacWhinney B, Craik FIM
Psychological
Science OnlineFirst, published on May 5, 2015 as
doi:10.1177/0956797615573759
III. The Counter-response
The
Connection Is in the Data: We Should Consider Them All
de
Bruin A, Treccani B, Della Sala S
Psychological
Science OnlineFirst, published on May 5, 2015 as
doi:10.1177/0956797615583443
Bialystok
et al. The implication of their argument is that this publication
bias invalidates the credibility of the positive published evidence.
These are serious charges and need to be carefully scrutinized.
De
Bruin et al. We are not part of a camp that is for or against the
bilingual-advantage hypothesis and have in fact published a study
supporting this hypothesis ourselves (Treccani, Argyri, Sorace, &
Della Sala, 2009).
Bialystok
et al. Their conclusion, however, is undermined by three errors in
reasoning that concern (a) the relation between conference abstracts
and published articles.,
[The
authors] used conference abstracts as a proxy, but there is no way of
knowing how many abstracts that reported positive results and how
many that reported negative results were submitted for publication.
De
Bruin et al. […] in our article, we sent out a short ad hoc
questionnaire to all first authors of unpublished abstracts.
Unfortunately, 33 of the 52 authors contacted did not reply or
refused to fill in the questionnaire... [...] This suggests that more
than half of the null or negative findings had not been submitted.
Bialystok
et al. (b) the difference between null and negative findings.
If
the main point of the article is to demonstrate that journals prefer
to publish articles that show significant effects over those that
show no effects, then their point is correct, and no further analyses
are needed.
[…]
It seems, therefore, that the real purpose of the de Bruin et al.
article is to use publication bias as a means of discrediting
evidence for bilingual effects on cognition.
De
Bruin et al. In our article, we clearly acknowledged that an equal
number of disadvantages and advantages should be found if there is no
advantage at all.
[…]
in the absence of a theoretical motivation for monolingual
executive-control advantages, a bilingual disadvantage is likely to
be interpreted as the result of a Type I error.
Bialystok
et al. (c) the differential effects of bilingualism on verbal and
nonverbal task performance.
The
finding of fewer cases of published negative results is not bias but
rather a reflection of the use of verbal tasks.
De
Bruin et al. [...] we did not include conference abstracts that discuss
lexical tasks without an executive-control component. We did include
executive-control tasks with verbal materials, in which, according to
the studies mentioned by Bialystok et al. themselves (e.g.,
Bialystok, 2009), bilinguals should outperform monolinguals.
However,
when we do exclude all studies using verbal materials from our
analysis [...] The outcome is not affected by the nature of the
materials.
Bialystok
et al. [...] a large and growing body of literature not only
indicates that these changes are real but also increasingly points to
the brain mechanisms by which these changes occur (Green &
Abutalebi, 2013).
De
Bruin et al. We agree that there are many interesting and compelling
data supporting an advantage (e.g., Pliatsikas, Moschopoulou, &
Saddy, 2015). Yet evidence for a bilingual advantage is far from
accepted wisdom. Indeed, the number of studies challenging such an
advantage has recently been increasing (e.g., Lawton, Gasquoine, &
Weimer, 2014; Paap, Johnson, & Sawi, 2014).
And
to conclude:
Bialystok
et al. Not every study of climate change that samples weather
conditions from a specific time and place finds that temperatures are
rising, but researchers (mostly) accept that climate change is
occurring because of global warming.
De
Bruin et al. Publication biases may be worsened by researchers’ own
prejudices or agenda. Bialystok and her colleagues have doubted the
value of null results, asserting that “the considerable literature
that reports group differences between monolingual and bilingual
participants is greatly more informative than the attempted
replications that fail to find significance” (Kroll &
Bialystok, 2013, p. 502). [...] We disagree with the logic underlying
this supposition.
I
highly recommend to read
these articles.
On this topic:
- Is bilingualism really an advantage by Maria Konnikova
- My conversation with Barbara Treccani (in Italian)
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