studies have found that one or both of the two components that characterise
the ERP responses to syntactic violations in monolinguals, the (E)LAN and
the P600, are absent in the case of bilinguals (Hahne, 2001; Hahne &
Friederici, 2001; Weber-Fox & Neville, 1996). However, this difference
between bilinguals and monolinguals is most prominent when the bilingual
group consists of participants that were exposed to the second language (L2)
later in life and are less proficient in it. (See also Chapter 4 for discussion of
variations across types of bilingual speakers.) For example, Hahne (2001) pre-
sented sentences with syntactic violations to monolingual German speakers
and to speakers of Russian who had started learning German after the age of
ten. The results indicate that the ELAN component and the late positivity
that were present in the ER Ps of the monolingual German group, were absent
in the case of the bilingual group. On the other hand, highly proficient bilin-
guals that were exposed to both languages during childhood, tend to display
the same components as monolinguals (Weber-Fox & Neville, 1996).
In sum, electrophysiological studies on syntactic violations in bilin-
guals show, somewhat unsurprisingly, that age of acquisition and proficiency
level play an important role in how the human brain processes two languages.
The earlier the exposure to the L2 starts and the higher the level of profi-
ciency, the more the ERP responses of the bilingual brain resemble those of a
monolingual one (see also Zawiszewski, 2007; for an overview see Kotz, 2009;
also Chapters 2, 4 and 5 this volume for further discussion of age effects).
This result however tells us nothing about the possibility that grammati-
cal processing in a given language may be influenced by knowledge of another
language. Could we show that a syntactic difference between two languages
causes the bilingual brain to process language differently, when compared
to the monolingual brain? Crucially, could these differences be detected
when the bilingual is being exposed to input from one language only?
Interestingly, this line of thought has recently been followed in domains
outside syntactic processing, namely in lexical activation. Recent research
(e.g. Dijkstra et al., 1999; Dijkstra & van Heuven, 2002; Kroll & Stewart,
1994) has shown that semantic, orthographic and phonological similarities
between pairs of words in the two languages of a bilingual can affect the
bilingual’s performance and/or patterns of brain activity in a variety of tasks.
These effects are present even when the task consists of material which
comes exclusively from one of the two languages of the bilingual participant.
This type of evidence suggests that the two languages of a bilingual interact,
and processing in one of the two languages is influenced by knowledge of the
other language. In a recent study using ERPs, Thierry and Wu (2007) exposed
Chinese-English bilinguals and English monolinguals to English words, some
of which concealed a character repetition when translated into Chinese. Even
though the experiment was conducted in an all-English language context,
the hidden character repetition created a significant modulation in the brain
potentials of the bilingual participants. Such results indicate that when
216 Part 5: The Bilingual Brain