Effect of bilingualism on verbal fluency tasks and a standardized neuropsychological assessment battery, in Polish-speaking sample

Introduction

Clinical neuropsychology is a branch of psychology (and neurology) the aim of which is to understand how the structure and function of the brain relates to psychological process and behaviour. It's one of the disciplines of psychology that overlaps with neuroscience, neurology, and even psychiatry. It involves assessing and treating patients who suffer brain illness or injury causing neurocognitive problems. It brings a psychological approach to treatment, by analysing the relationship between injury and dysfunctional behaviour. The core tool used here is a neuropsychological test battery. This usually consists of a number of tasks that examine specific cognitive process, such as memory, learning, language production, and intelligence. These tests are standardized and based on normative data collected from healthy individuals. The obtained general results can be used to compare performances of potential patients against those standardized. Thus, the patient's cognitive abilities can be measured.(Lezak, Howison,Loring 2004)

As one can see, the importance of a standardized neuropsychological test is necessary for the correct estimation of brain dysfunction and appropriate treatment to be applied. For example, neuropsychological assessment can aid in the treatment of patients with Alzheimer's disease by providing important information in order to tackle specific issues.

18th century philosophers, including Locke and Hume provided one with a strong assumption that cognitive abilities are universal. This approach was commonly accepted and visible in practical tests till the 20th century. It was also strengthened by the analogy of the human brain as computer hardware. (Block,1995). This would strongly suggest that the processes of interest in neuropsycholology assessment are generally presumed to be the same among all human beings. The most common battery test has been created in the United States and other western European countries such as the United Kingdom. They provide normative-sample data against which the human race has been assessed. (Nell, 1994)

Nerveless, in the last thirty years a very influential debate has begun, that developed a growing interest in cross-cultural research. The relationship between culture, language and cognition became focus of interest in many disciplines. Neuropsychology faced a challenge to its usefulness posed by the need for cross-cultural sensitivity. (Vijer, Hambleton,1996). Thus, a question could be raised: are cognitive abilities exactly the same for all healthy individuals across the globe? Or do they vary among different environments, cultures and social settings? If so, that means that standardized test should result from culture sensitive data. The neuropsychological tests should be a framework that reflects minority and culture specific differences rather than putative universalism.

Benjamin Lee Whorf believed that linguistic patterns in different languages have an impact on people's habitual thinking. According to him, the linguistic differences shape, and affect the way individuals perceive and remember. Thus, in his view culture and language can not be analysed separately (Whorf,1956). He conducted most of his research among the Native American people, on who he based his core assumptions.

Whorf's idea was taken up by Vygotsky in 1962 ,who also believed that language plays an essential role in the development of cognitive processes (Vygotsky,1962). This can be supported by the recent study by Borodistky in 2001, who has shown the differences in how English and Mandarin speakers perceive time. For example, Mandarin understand time as if it was vertical, and English as if it was horizontal. (Boroditsky,2001)

With the increasing interest in cross-cultural research, the literature provides one with a constantly growing number of examples of cognitive processes being malleable rather than fixed across all human. Lucy in 1992 examined differences in cognitive performance between Mayan and English speakers. He found that there were significant differences in the way the two groups attended to nominal number(Lucy, 1992).

Levinson and his colleagues in 1998 has shown that the Mexican Indians of Tzeltal discourse, unlike western languages, does not use the words left or right to describe spatial orientation. This language characteristic mirrored the way they solved visual puzzle tasks (Pederson,Danziger,Levinson et al,1998)

The other research by Nisbett and his colleagues provided further evidence for cultural and language biases. They compared performances of adults from China and the United States on numerically and spatially based measures of speed of processing and working memory. The author has found numerically based tasks to be cultural biased.

Nisbett also showed that cognitive, and perceptual processes can be shaped by cultural practices. For example, East Asians have a holistic approach to thinking, and ignore formal logic. In contrast, Westerns have an analytical approach, they are attentive to object category, using rules of formal logic. The authors suggested that the differences emerge from each nations social systems (Nisbett, Choi, Peng, Norenzayan, 2001).

The body of evidence in the literature clearly shows that cross-cultural aspect has an enormous effect on the results obtained in neuropsychological assessments. It is unlikely a "one size fits all" battery can remain in usage. One can suggest that the standardized test has suffered from a lack of ecological validity. The limitations on those test practises can undoubtedly affect the quality of the assessment, and what follows effects the treatment. The test norms set for dominant western culture can not truly evaluate the cognitive abilities in other individuals (Ardila, 2000).

For most neurophysiologists the concept of norms should be understood not only as statistical properties, but also as main variables applied across cultures. The evaluation of patients' responses in neuropsychological examination must consider then the contribution of specific social, and cultural experiences.

One of the solutions for this problem could be a translation of instruments into the target language. However, this should be treated with caution, as the translation could be inadequate, and skew the outcome (Nisbett et al, 2001). For example Vijer (2002) shows that the Swedish translation of " The bird with webbed feet" on one task is "bird with swimming feet", this provides a testee with a better clue to the answer. Hence, the results are not valid.

Inappropriate test items also introduce items bias. The newly introduced content may sample undesirable domains and automatically has a negative impact on psychometric properties. Therefore, the translation always requires some effort.

Perhaps, the most daunting element effecting neuropsychological research is different levels of education. For example, in Western society adults will be able to count to twenty and say the alphabet in five seconds. However, the South African labourer with average of 6 years of education took an average of 9.3 seconds ( Nell, 1994). Thus, it is plausible to assume that all the above-mentioned features can be omitted in neuropsychological assessment. When performing experiments on logical thinking or memory the data must be applied locally to people raised in a specific tradition. All psychological assessment faces the problem of culture and cognition, but the most affected group are neuropsychologists. They remain in hospital settings where universality of diagnosis is unchallenged.

In response to this evidence there is an urgent need in cross-cultural neuropsychological research to develop new, reliable normative data that reflects different nations' habits of thinking.

Thus, the primary objective of this study is an attempt to establish a set of normative data for a brief battery of cognitive tests in Polish native speakers currently living in United Kingdom. The analysis will also include demographical variables, and performance in term of education, length of residency in the UK, and level of proficiency with the English language.

As changes in communication technology, and the global economy are constantly closing the gap between nations, creating an almost global "village", more often countries become mulitculturistic and cosmopolitan. Constant migration changes the shape, and size of subculture all over the world. After the end of the Second World War around 300,000 Polish exiles settled in Great Britain. Over the following years, the number of Poles in UK has changed. Some of them return to Poland and some of them have created lives in England.

In 2001 National Statistics have shown, that almost 60,000 Poles lived in England and Wales. A dramatic increase in the number of Polish immigrants was visible after May 2004, when this country became part of the European Union. From that date over 350,000 Polish have applied for work permits in the UK: 65% of total arrivals from new parties of the EU ( Accession Monitoring Report, 2006). Study, work, and search for new opportunities are the main reason for migration. At the same time, in order to achieve their goals, they must adjust to a new culture and communicate in the local language, which is English. As a result of these social processes there are large numbers of Polish immigrants who are bilingual.

The term bilingual varies throughout the literature on the topic. Some authors focus on equal passive competence in both languages, for example reading equally well, whereas others focus on equal production, such as speaking or writing (Albert, Obler,1978), but in general, bilingualism is the ability to conduct aspects of everyday life in two languages. The proficiency in both languages varies in each individual and depends on many factors. Still, people who are bilingual are more often familiar with one language than another, this is caused by learning one of the languages when growing up, and learn the other subsequently. ( Albert, et al,1978) Thus, the use of the term "bilingual" is depended upon context, linguistic proficiency, and ranges across the continuum.

The complexity of this topic must be also considered in neuropsychological tests. Although bilingual individuals may appear conversationally fluent in both languages, they may not have been exposed to the same culture-specific information in either language. For example a native Polish speaker will find it more difficult to express their opinion or talk in detail about the English government than an English native. Lezak highlights that a neuropsychological battery must be sensitive to bilingual performances, as those who moved to a new culture and adopted a new language are likely to have different linguistic capabilities (Lezak,Howison&Loring 2004)

In 1994 Kaufman presented data that indicates that the majority of Spanish children (even those who are equally fluent in English) have shown significant differences in WISC-III, between their Verbal Scale IQs and Performances Scale IQs (Kaufmann & Kaufmann,1994).

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