Multilingualism refers to speaking multiple languages. It is not just a technical task which only requires a cognitive dimension as it also has emotional, social and cultural significance. There are three dimensions for describing people’s associations with the languages they speak:

• Expertise
  This refers to the degree of proficiency in a language.
• Affiliation
  This refers to the affective relationship with a language.
• Inheritance
  This refers to the membership of a certain language group (e.g. by birth; family; community).

Simultaneous multilingualism (i.e. balanced bilingual) refers to learning the first and second language simultaneously. Both languages are learned in the home environment and the level of both languages is maximal depending on socioeconomic status and input. Successive multilingualism (i.e. functional bilingual) refers to learning the first language first and the second language after mastering the first one. The first language is learned in the home environment whereas the second language is learned at school or work. The level of the first language is maximal but the level of the second language varies. This multilingualism can be domain-specific (e.g. only reading; only speaking).

Lower order processes refer to the level of letter and word recognition. Higher-order processes refer to the comprehension of the content of text. Efficient lower-order processes allow to allocate optimal attention to the interpretation of meaning communicated in the text. Metacognitive skills in reading refer to the ability to use strategies to regulate the reading process.

When learning a language at home, exposure to the best language is essential. It appears as if the first language skill can predict second language learning early on in life. This could help with early diagnoses of reading and spelling problems of the second language. There are several theories as to how the first language influences learning the second:

1. Linguistic interdependence hypothesis
   This states that there is knowledge transfer from the first to the second language. There is metalinguistic transfer and higher-order skills (e.g. reading strategies) can be transferred from the first to second language. This is believed to aid language acquisition.
2. Threshold hypothesis
   This states that there needs to be a knowledge threshold before higher-order skills can be transferred. This holds that reading strategies from the first language can be used in the second language when there is enough knowledge of the second language (e.g. sufficient vocabulary in the second language).
3. Automaticity hypothesis/transfer facilitation model
   This states that for transfer of knowledge to occur, the word recognition (i.e. decoding skills) in the second language needs to be automatic past a threshold. For this to occur, the orthographies of the two languages need to be comparable. A good command of skills (e.g. reading strategies) in the first language is needed and this can be transferred if decoding is automatic in the second language.

In a structural model of languages, there are relations between skills in language one and language two. Lower order skills (e.g. vocabulary; syntax; word recognition) seem to be language-dependent and there is no transfer of skill. However, for higher-order skills (e.g. metacognition; reading strategies), this seems to be language independent. This means that transfer of skill is possible. The higher-order skills only seem to transfer when there is sufficient knowledge (e.g. vocabulary) of the second language. The speed of word recognition is unrelated to potential transfer, meaning that this does not provide support for the automaticity hypothesis. This does provide support for the threshold hypothesis.

For the first language, only metacognitive knowledge is important whereas vocabulary knowledge and metacognitive knowledge are important for reading comprehension in the second language. Processing speed does not contribute significantly to the reading comprehension of either language. A higher-order processing speed is important for reading comprehension of the first language.

One of the most important factors in explaining individual differences in second language learning is motivation. Extramural English exposure refers to English outside of a classroom (e.g. in the media).

Vocabulary is essential for learning a second language. Extramural exposure and formal exposure play an indirect role in vocabulary learning. Motivational factors mediate the relationship between different types of extramural exposure and vocabulary knowledge. Formal group linguistic self-confidence also mediates this relationship.

In research on multilingualism, dyslexic people are often overlooked while multilinguals can have dyslexia. The overall language competence and not just competence in one language needs to be assessed. There is an IQ-achievement discrepancy definition for dyslexia and this is problematic for multilinguals because:

• The IQ scores of immigrant children become more similar to native children with length of stay.
• There is a five to seven-year period for the development of cognitive-academic language proficiency in an additional language.
• There is often avoidance of IQ testing with bilingual students.
• IQ measured in a second language lacks reliability and validity.

This means that IQ is likely to be underestimated, making it more difficult to assess whether there is an IQ-achievement discrepancy in bilingual children. This makes it more difficult to give them an appropriate diagnosis of a specific learning disorder (e.g. dyslexia).

When teaching bilingual children with dyslexia, it is important to evaluate the balance between the needs of second language learners and needs related to dyslexia. Needs for second language learners include reading for meaning. Needs of students with dyslexia include addressing phonological skills more directly. However, there is a risk that exercises from dyslexia programmes do not work when learners have a limited vocabulary in the target language (e.g. in the case of bilinguals). There are five major challenges when it comes to research and practice with multilingualism and dyslexia:

1. Identification
   This includes learning where to look to identify dyslexia in bilingual children.
2. Defining dyslexia
   This includes having a clear working model of dyslexia and not an IQ-achievement discrepancy definition.
3. Defining bilingualism
   This includes taking into account the dimensions of expertise (1), affiliation (2) and inheritance (3).
4. Teaching strategies
   This includes achieving the best balance between the child’s needs.
5. Involving families
   This includes finding effective strategies for supporting families to play an active part in the children’s progress towards literacy.

There are five problem areas in a school context due to cultural differences:

1. Non-verbal communication
   The way children communicate non-verbally depend on the culture (e.g. looking somebody in the eyes or not).
2. Communication style
   The communication style may differ per culture and thus at home and school.
3. Group versus individual orientation
   The orientation (i.e. individualistic; collectivistic) of a child may differ per culture.
4. Conflicting norms and values
   The norms and values of children may differ per culture (e.g. position vs. independence).
5. Structure in surroundings
   The structure may differ per culture (e.g. strong and clear structure at home vs. malleable structure at school).

For immigrants, social skill training may be necessary. This includes tackling the insufficient command of social situations (1), insufficient knowledge of codes (e.g. way of communicating) (2) and using the incorrect codes (3). This helps children learn additional roles, leading to integration rather than assimilation. It is important to not make any assumptions about a culture.

Acculturation refers to the phenomena which occur when groups of individuals having different cultures come into continuous first-hand contact. This leads to changes in the original cultural patterns of either or both groups. According to unidimensional models, acculturation is a process of change in the direction of the mainstream culture. Bidimensional models hold that there is an adaptation dimension and cultural maintenance dimension of acculturation.

Hutnik proposed a distinction between cultural change (i.e. acculturation) and self-categorization (i.e. identity). This is a two-dimensional model of acculturation. It combines identification with the ethnic minority group and the majority group. There are four identity strategies:

1. Acculturative (i.e. hyphenated identity)
2. Assimilative (i.e. predominant majority identity)
3. Dissociative (i.e. embedded minority identity)
4. Marginal (i.e. indifferent identity)

Resistance to acculturation is most persistent with regard to identity aspects and least with contact aspects of acculturation. The attitudes towards cultural change tend to be in the middle of this continuum (e.g. resistance to change increases when cultural distance is larger).

There are individual differences in cognitive, emotional and motivational determinants of acculturation. Psychological assessment needs to take these individual differences of acculturation into account rather than generalize the acculturation of a minority group as a whole. The adjustment dimension is more relevant than the cultural maintenance dimension. It allows to determine whether a person belongs to a population for which an instrument (e.g. IQ test) has been developed and it allows to determine whether the instrument is suitable for a particular person to measure the intended construct. Assessment outcomes need to be interpreted with the answers to these questions in mind.

It is important to assess acculturation because of three reasons:

• It allows to identify problems in the acculturation process.
• It allows for detection of acculturation-based biases in psychological tests.
• It has a pervasive influence on behaviour and knowledge and should thus be mapped.

When assessing acculturation, it is possible to ask people a single question pertaining to what culture they value most (1), ask two questions regarding how they value adapting and maintaining the culture (2) or four questions regarding each acculturation strategy (3). To approach the potential cultural bias in instruments it is possible to use cut-off scores (1), use hard acculturation data to establish norms (2), use acculturation as a covariate or moderator (3), use standardization or centring (4), use the item response theory (5), use method factors (6) or use the person-fit tradition (7).

Berry’s acculturation model assumes that acculturation strategies have trait characteristics and are the preferred strategy in all domains of life. The contextual acculturation model states that acculturation orientations are simultaneously influenced by pressure from the ethnic community and the host society. The preferred strategy may differ per domain. For example, in the public domain, the norms of the dominant group are most salient and influential. In the private domain, the ethnic in-group norms are most salient and most easily enforced. Acculturation strategies may thus differ depending on the context. When assessing acculturation is it necessary to look at both the public and private domain and to take attitudes into account.

There are two possible outcomes of acculturation. Psychological adjustment includes subjective well-being (1), satisfaction self-esteem (2) and psychological health (3). It is associated with a stress-and-coping approach of acculturation. This is predicted by high levels of social support (1), low incidence of life changes (2) and an internal locus of control (3). Sociocultural adaptation is related to learning processes and involves the acquisition of effective behaviours (1), social skills (2), language mastery (3) and cultural knowledge (4). This is predicted by a longer period of residence (1), a smaller cultural distance at group level (2), more frequent interactions with host nationals (3), more favourable attitudes toward cross-cultural adaptation (4), more emotional stability (5) and more extraversion (6).

The distinction between both types of outcomes of acculturation is important for assessment. When assessing competence-related behaviours in an academic or professional setting, it is important to look at attitudes towards adaptation (1), length of residence (2), cultural distance (3), language mastery (4), extraversion (5), achievement motivation (6) and social contacts and skills (7). When assessing psychological disturbances, it is important to assess positive attitudes towards cultural maintenance as this may be a source of psychological security and self-worth.

An item or instrument is biased if it does not have the same meaning for a different group (e.g. migrants vs. non-migrants). There are several types of bias:

1. Construct bias
   This refers to an incomplete identity of a construct across groups or incomplete overlap of behaviours associated with the construct (e.g. characteristics of being a good son or daughter; this changes per culture). This means that a construct cannot be used in both groups.
2. Method bias
   This can result from sample incomparability (1), instrument characteristics (2), tester and interviewer effects (3) and the mode of administration (4).
3. Anomalies at item level (i.e. item bias)
   This occurs when people with the same standing on an underlying construct (e.g. intelligence) do not have the same average score on the item because it favours one cultural group.

The identification and prevention of construct bias typically require thorough knowledge of the society of origin and in-depth interviews and field observations. The method bias can be alleviated by using a detailed protocol and having trained administrators. The item bias can be alleviated by using psychometrics.

The rates of adjustment are in between the extremes in practice. Migration is stressful and it impacts psychological development. It is therefore important to focus on psychological adjustment and sociocultural adaptation.

Children are vulnerable to changes due to migration and acculturation. Adolescents are at particular risk to develop psychological problems. Needing to function in different cultural contexts (e.g. family; peers; institutions of society) can lead to feelings of alienation. Difficulties with language acquisition (1), integration in the educational system (2), racism (3) and identity (4) during adolescence may lead to behavioural and emotional problems.

Moroccan parents report similar levels of problems for their children compared to Dutch parents. However, teachers report more externalizing problems for Moroccan children than for Dutch children and the Moroccan adolescents report fewer problems than Dutch adolescents.

Turkish parents report more problem behaviour than Moroccan and Dutch parents. However, adolescents themselves do not report any differences. Teachers did not report more problem behaviour for Turkish adolescents compared to Moroccan adolescents. The differences between Moroccan and Turkish parents are most striking between the age of four and eleven. Teachers report more externalizing problems for Moroccan children than for Turkish children but for adolescents, they have fewer problems.

The effect of migration and acculturation on two immigration populations can be different. This may be due to the size of the cultural gap that has to be bridged. However, this is debated. The results may be explained by true differences in children’s behaviour (1), perceptual biases (2), social desirability (3) and different thresholds to report problem behaviours (4). Differences may occur due to methodological differences (1), different informants (2) and different cultures (3). Culture may influence expectancies and beliefs regarding children and this may influence distress felt concerning particular kinds of child behaviour. It may also influence the threshold for parents to report something as problem behaviour (e.g. behaviour has to be deviant from culture of origin rather than host culture to be seen as problematic).