Differential bilingual laterality: mythical monster found in Wales

Differential bilingual laterality: mythicalmonster found in Wales

Judith Evans, Lance Workman,* Peter Mayer,and Kevin Crowley

School of Humanities and Social Sciences, University of Glamorgan, Pontypridd,

Wales, CF37 1DL, United Kingdom

Accepted 5 December 2001

Abstract

Paradis (1992) likens studies of bilingual laterality to reported sightings of the Loch Ness

Monster, in that although some studies claim differential laterality much conflicting research

evidence does not—and like the mythical Scottish monster, what reason have we to suspect

that any such phenomenon might exist? This study reexamines differential bilingual laterality

using four groups of English–Welsh bilinguals which differ in their age of acquisition and in

their environment of acquisition. Using a split visual field paradigm we present evidence

which, supports the notion of greater right hemisphere processing in a later learned language.

Our findings also suggest the pattern of lateralization in bilinguals is strongly affected by the

specific language environment during development such that the shift toward greater right

hemisphere involvement for the later learned language will be more pronounced in individuals

which are brought up in areas where that language is not regularly heard. � 2002 Elsevier

Science (USA). All rights reserved.

Keywords: Bilingual; Laterality; Evolutionary; Acquisition; Environment; Age

1. Background

In 1967, Erich Lenneberg proposed that language acquisition is governed by the

maturation of the left and right cerebral hemispheres such that normal left hemi-

sphere superiority is not completed until around puberty (Lenneberg, 1967). If this is

the case then the age of acquisition of a language might affect the degree to which it is

lateralized (Krashen, 1973). Following Lenneberg’s claim, a number of researchers

have suggested that a second language which is learned following maturation of the

nervous system might make greater use of the right hemisphere than one learned atan earlier age (Albanese, 1985; Genesee et al., 1978; Vaid, 1983). In order to explore

this right-hemisphere shift hypothesis for later learned languages, such researchers

Brain and Language 83 (2002) 291–299

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E-mail address: [email protected] (L. Workman).

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have applied split-screen and dichotic listening paradigms to bilingual participantswho vary in their age of acquisition for the two languages. If a later learned language

makes greater use of the right hemisphere then this should be reflected in the pattern

of ear and lateral visual field advantage.

Some studies have provided clear support for this right shift hypothesis for later

learned languages. Genesee et al. (1978), for example, found that English–French

bilinguals who learned their second language after the age of 12 made greater use of

the right hemisphere when categorizing words. Likewise, Wuillemin, Richardson,

and Lynch (1994) found that in Papua New Guinean subjects, late acquirers of bothEnglish and Tok Pisin demonstrated a greater right hemisphere involvement than

early acquirers (see also Albert & Obler, 1978; Shanon, 1982; Vaid & Lambert,

1979). In contrast, however, a number of other studies have failed to substantiate the

notion of a late right shift (see for example, Furtado & Webster, 1991; Hoosain,

1992; Wesche & Schneiderman, 1982).

Such mixed findings have led Michel Paradis to dismiss research into bilingual

laterality as fruitless, caricaturing it as a search for a mythical monster (Paradis,

1990, 1992, 1995). In addition to a general dismissal of the right-shift hypothesisParadis is highly critical of the experimental methods employed by researchers in this

area suggesting that experimental studies of bilingual laterality require more strin-

gent subject selection and more clearly defined standardized methods than have

generally hitherto been adopted (Paradis, 1990, 1992, 1995). This view is shared by

Vaid and Hall who commented that ‘‘differences in method, task and stimulus

characteristics have been shown to affect patterns of asymmetries’’ (Vaid & Hall,

1991; see also Hellige, Bloch, & Taylor, 1988; Sergent & Hellige, 1986).

Although the precise relationship between language development and normalhuman lateralization is an area of unresolved debate, the evidence that there is a

relationship between age and ability to learn a new language is unequivocal (Cor-

ballis, 1991). The older a person is when learning a second language the greater the

amount of effort required. Moreover, universally, language is well established by the

age of 4, suggesting that this early period of linguistic development is a human

adaptation (Corballis, 1991; Lenneberg, 1967; Pinker, 1994; see also Johnson &

Newport, 1989). At some stage following the first 4 years of life acquisition certainly

becomes increasingly more difficult. Suggestions for the precise age at which ac-quiring a new language becomes arduous vary somewhat but most workers would

agree that it is difficult to develop full linguistic skill for a language learned after the

age of around 5 or 6 (Corballis, 1991; Pinker, 1994).

2. The importance of the linguistic environment

Clearly, the proficiency gained in each of a bilingual’s languages depends not onlyon the age of acquisition but also on the precise nature of the linguistic environment

during development. Jackendoff (1993) explains the ‘‘paradox of language acquisi-

tion’’ with a ‘‘genetic hypothesis’’ suggesting that the young child’s task in acquiring

language is more like adjusting a TV set to tune it in to the correct channel rather

than ‘‘inventing it again or figuring out how it works (which is the linguists task).’’

Perhaps for bilinguals who are exposed to a dual-language environment, during the

normal period for language acquisition, all they have to do is tune into two channels

instead of one?In line with the right-shift hypothesis we would only expect greater right-hemi-

spheric involvement if not exposed to the characteristic features of a later learned

language until the child has matured past the normal age of acquisition (and

292 J. Evans et al. / Brain and Language 83 (2002) 291–299

therefore has to adopt different learning strategies). As Strozer (1994) comments‘‘adults still have access to the invariant principles of language, but they do not have

access to the direct re-setting of parameters.’’

In the current study, we make use of a population in which childhood linguistic

experience varies considerably within a relatively small geographical area, i.e., the

southern and western counties of Wales. Some countries contain predominantly

monolingual English speakers whereas others contain a large number of English–

Welsh and Welsh–English bilinguals. By making use of this natural variability in

linguistic experience we aim to reexamine the notion of a greater involvement of theright hemisphere in a later learned second language. Using a split-visual field par-

adigm we predict that, in a single-language environment, late acquisition of a second

language will result in left visual field (right-hemisphere) advantage for that lan-

guage, when compared with early acquisition of the second language. Furthermore,

we propose that in a dual-language environment, both early and late acquisition of a

second language will result in a right visual field (left-hemisphere) advantage for that

language, due to the exposure to both languages. In all cases the second language

acquired is Welsh.

3. Method

A variety of methodological problems have been documented in a number of

previous lateralization studies. These include problems of not controlling for age,

stage, and manner of acquisition (Vaid & Genesee, 1980); inconsistency of test

stimulus between groups (Young & Ellis, 1981); not controlling for the factors ofhandedness, gender, and general language environment (Obler, Zatorre, Gallo-

way, & Vaid, 1982); and a general lack of uniformity of test procedures (Bryden

& Mondor, 1991). Additionally, we would suggest the need for stated proficiency

criteria in relation to test material and consistency of measurement criteria.

Therefore, this study adopts precise subject selection and a standardized method

over a series of interrelated experiments to create a fresh pool of comparable

data.

Subjects. One hundred twenty English–Welsh bilinguals formed four distinctgroups, differing in age of acquisition of Welsh, as a second language, and general

language environment. All subjects were right-handed, 15 to 16 years old at time of

testing, and Welsh GCSE (General Certificate of Secondary Education) candidates,

to establish a proficiency criteria in relation to the test material. Each experimental

group comprised 30 subjects (15 males, 15 females) from the same general language

environment and with the same age of acquisition of Welsh. All groups completed

the same visual half-field test for single word recognition.

Target stimuli. Subjects were exposed to the random, computerized, split-screenpresentation of 80 words (40 English and 40 Welsh) on a standard VDU and

required to type their responses on a standard keyboard (which they were fa-

miliar with). All target stimuli were familiar, regular, high-frequency, concrete

nouns—which were verified by a Welsh Advisory teacher for schools—to ensure

that all subjects had at least 4 to 5 years prior regular exposure to these simple

words which would thus be easily recognizable. It is well established that early

acquired words are more easily recognized than later learned ones (Taylor &

Taylor, 1990). Stimulus words were all simple nouns, commonly found in youngchildren’s literature—and these were assessed by relevant language teachers to

ensure that all subjects would be familiar with the translations from the school

curriculum.

J. Evans et al. / Brain and Language 83 (2002) 291–299 293

A number of other controls were made for the words used in this study. Giventhat high-frequency words are easier to recognize than low-frequency ones, only

words rated as high-frequency were used (Kucera & Nelson Frances, 1967). Also

high-frequency words tend to be learned earlier in life and correlate with ‘‘con-

creteness’’ (Ellis, 1983). Therefore, as concreteness correlates with frequency and

earlier learned words, stimulus words were selected for their concrete value (Paivio,

Yuille, & Madigan, 1968). Additionally, stimulus words were regular, with regularity

here being defined as ‘‘straightforwardly predictable from their spelling to anyone

who knows the normal correspondences between the letters and the sounds of thelanguage’’ (Ellis, 1983).

Studies have indicated that the left-hemisphere recognition advantage increases as

the length of the target word presented increases (Young & Ellis, 1981). Within the

constraints of the above mentioned criteria, efforts were made to select words which

were similar in length and in their translations. For 30% of the stimulus words the

Welsh equivalent was longer than the English, for 25% of the words the English was

longer than the Welsh equivalent and in 45% of cases the words and their transla-

tions were of equal length.Procedure. All subjects completed the same questionnaire prior to selection to

clearly establish language history in respect of age, stage and manner of acquisition,

handedness, gender, and language environment during early development. All sub-

jects were given the same target stimuli, and in every case there was uniformity of

position, distance (sitting 60 cm from the screen) and exposure duration (150ms). A

cross (a fixation marker) appeared in the center of the screen immediately prior to

each target word appearing on either the right or the left visual field in order to

standardize fixation. Target words appeared to the left or the right of the fixationpoint with their inner edges at 1.8� from this point when viewed at 60 cm. All subjectswere given the same instructions and familiarization with equipment and test pro-

cedure by an initial block of 10 practice words.

Indices of laterality. There are uniquely varying degrees of human laterality

(Springer & Deutsch, 1998). Moreover, previous testing demonstrated a great deal

of variation in the ability of school students to identify words presented very briefly

to them. With these factors in mind, measurement was uniform, with a ratio

analysis undertaken, by calculating an index of laterality for each subject for bothEnglish and Welsh word recognition. Subjects’ raw scores (i.e., number of words

recognized in each language in each visual field) were converted to a ratio mea-

surement ranging from +1 (indicating total left-hemisphere dominance for visual

word recognition) to )1 (indicating total right-hemisphere dominance for visualword recognition). These individual indices of laterality were then subjected to

analysis of variance.

Language environments. Subjects were drawn from two areas of Wales, which,

although geographically close, are linguistically quite distinct. The operational cri-teria for a dual-language environment was that 40% or more of the county’s pop-

ulation aged 3 years and over spoke both English and Welsh habitually (as

determined by the last published Census Survey). Thus, two groups were drawn from

the Welsh county of Dyfed (defined as a dual-language area), and two groups were

drawn from the Welsh counties of South and Mid Glamorgan (defined as single-

language, i.e., English areas) (See Fig. 1.)

Experimental groups:

Group 1: Welsh acquisition prior to 5–6 years old; single-language environment.Group 2: Welsh acquisition after 5–6 years old; single-language environment.

Group 3: Welsh acquisition prior to 5–6 years old; dual-language environment.

Group 4: Welsh acquisition after 5–6 years old; dual-language environment.


4. Results

These descriptive results, representing the mean indices of laterality for each ex-perimental group, show a right-hemisphere effect only for later-learned Welsh in a

single English language environment (i.e., Group 2), as hypothesized (Fig. 2).

Three-factor analysis of variance revealed a significant difference between the

early and later acquisition of Welsh, as a second language in a single-language en-

vironment (for Groups 1 and 2 there is a between-subjects effect for age of acqui-

sition where F ð1; 58Þ ¼ 13:27, p < :001 and a within-subjects effect for age ofacquisition by language where F ð1; 58Þ ¼ 15:08, p < :001). Thus, in a single languageenvironment acquisition after the suggested normal period of acquisition resulted inincreased right-hemisphere involvement.

However, analysis of variance revealed no significant difference between the early

and later acquisition of Welsh, as a second language in a dual-language environment,

(for Groups 3 and 4 there is no between-subjects effect for age of acquisition,

F ð1; 58Þ ¼ 0:31, p ¼ :581 nor a within-subjects effect for age of acquisition by lan-guage; F ð1; 58Þ ¼ 0:001, p ¼ :949). Thus, in the dual language environment, acqui-

Fig. 1.


sition after the suggested normal period of development did not result in greater

right-hemisphere involvement.

5. Discussion

In respect of single word recognition, these results appear to support the pre-

diction of a shift toward the left visual field–right hemisphere for the later learned

language of Welsh, but only for participants who were not exposed to Welsh during

the early developmental period of language acquisition.

Considering first the two groups from dual-language environments, Group 4, wholearned Welsh after the early period, did not show the shift toward the right hemi-

sphere for this language. In fact this group exhibited a pattern of lateralization which

was identical to those who learned both English and Welsh from an early age in an

area where both were spoken (i.e., Group 3). Group 4 participants would have

spoken English at home and then learned Welsh after the age of 5 or 6 at school.

They would, however, have heard Welsh spoken around them during this early

period. Such findings suggest that the degree to which a language is processed by the

left hemisphere depends very much on the general language environment of earlydevelopment rather than the languages the child actually uses.

Turning to the results for participants from single language areas, the findings for

Group 1 suggest that being taught Welsh in an English monolingual environment

leads to a partial right shift, but that as Group 2 demonstrates, this is more pro-

Fig. 2.


nounced when Welsh is learned following the age of 5 or 6. When combining theresults from Groups 3 and 4 with these findings, it might be suggested that, in order

to observe the full effects of the right shift, it is necessary not only that children

acquire their second language after the age of 5 or 6 but also that this occurs in a

single language environment.

It has been suggested that the nature of the task material may be a significant

factor in producing different patterns of laterality in bilinguals (Vaid & Park, 1997).

However, in the present study both stimulus words and task procedures were con-

sistent for each group. Therefore, this would be an unlikely explanation for the cleardifference in the degree of laterality for Welsh exhibited by Group 2 when compared

to Groups 1, 3, and 4 on the same task.

While task-specific factors appear to be an unlikely explanation for the pattern of

bilingual laterality uncovered in the present study, another possible explanation is

that language-specific factors might be responsible (Vaid, 1983; Workman, Brook-

man, Mayer, Rees, & Belin, 2000). The English and Welsh languages are quite

dissimilar with respect to phonetic regularity. Welsh has a transparent orthography,

that is, words are written as they are pronounced, with none of the confusions thatcan arise due to the deeper orthography of English, as is illustrated by the varied

pronunciation of words such as cough, bough, through, though, and thorough

(Davies, 1993).

It has been suggested that the two cerebral hemispheres have different cognitive

styles, with the left hemisphere dealing better with a phonologically consistent lan-

guage than the right hemisphere (Coltheart, Patterson, & Marshall, 1980; Joanette,

Goulet, & Hannequin, 1990). In the present study, while there is a similarity across

all groups for the lateralized representation of English (as a first language), there is asignificant difference for the lateralized representation of Welsh as a second language

between Groups 2 and 4 (both acquiring Welsh after 5 or 6 years of age). This

difference in laterality indices for Welsh between these two groups renders a language

specific explanation unlikely.

Clearly, while these results suggest that the age of acquisition is of importance to

the neural basis of language, learning to use a language before or after the age of 5 or

6 is not sufficient in itself to explain the pattern of language laterality observed in our

participants. The present study suggests that an interaction between age and lan-guage environment mediates the lateralized representation of early and later learned

languages. Perhaps, the left hemisphere has become adapted to select language pa-

rameters from the linguistic environmental during an early period in life. If, however,

a language is not learned or even heard until beyond this period then more bilateral

or even right-hemisphere representation may develop. To return to Jackendoff’s

(1993) TV analogy, perhaps during an early period of life, the television contains

software which allows for automatic tuning into local channels but that beyond a

certain age this program is lost and effortful manual tuning is now required to receivenew channels.

A split-visual field test of single word recognition can never be used to explain the

full complexity of the cerebral representation of language. It might, however, provide

some insight into the possibility of differential bilingual laterality. In the present study

we used two languages, Welsh and English, which differ in that the former is more

phonetically consistent than the latter. If our suggestion that there will be a shift to-

ward the right hemisphere for a later learned language in monolingual communities is

to stand up to scrutiny over and above language specific effects then it should also beapparent for other later learned languages under similar circumstances. We would

suggest that second languages learned in English secondary schools such as French

and German would make for a good further test of this prediction.


In his criticisms of research on bilingual laterality studies Paradis (1995) proposesthat, in relation to basic or innate language function, we are compelled to assume

that ‘‘implicit linguistic competence is subserved by areas of the left cerebral hemi-

sphere in bilinguals and unilinguals alike.’’ He sees such research into this area as

misguided and likens it to a search for a nonexistent monster. The primitive, 2m

deep-sea fish known to biologists as the coelacanth was thought to be extinct for over

70 million years. In 1938, however, this monstrous prehistorical fish was found to be

alive and well, thriving in the deep waters off the coast of Madagascar. Sometimes

exotic monsters really do exist, if you know where to look.

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Differential bilingual laterality: mythical monster found in Wales

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