The Science of Bilingualism and CLIL Pedagogy

Posted on Nov 11, 2025 in Early Childhood Education

Module 1: Foundations of Bilingualism

In 1950, some educators believed that learning a second language (L2) during childhood would negatively impact the development of the first language (L1), potentially confusing the child. However, research later challenged this view.

Cummins’ Key Hypotheses

In 1980, Jim Cummins proposed two foundational hypotheses:

  1. Developmental Interdependence Hypothesis: This supports the idea that if children possess a strong level of organization and conceptual knowledge in their L1, they will be able to transfer and apply these skills when learning their L2.
  2. Common Underlying Proficiency (CUP): This hypothesis states that languages in the brain are not entirely separated. They share the same base of knowledge and abilities. Therefore, a student does not need to learn the ability of reading or organizing a text twice; they just need to apply these existing skills to the new language they are learning.

To explain CUP, Cummins uses the iceberg metaphor. On the surface, both languages appear separated, but underwater, they are connected, sharing the same cognitive bases. In education, this theory strongly supports bilingual programs that seek the improvement of the first language, especially in methods like Content and Language Integrated Learning (CLIL) or English as a Foreign Language (EFL).

Benefits of Bilingualism

The advantages of bilingualism can be divided into linguistic and cognitive benefits.

Linguistic Advantages

  • People who know a second language have greater communication opportunities, allowing them to interact with more people in more places than a monolingual person.
  • Bilingualism opens doors for working or studying in other countries.
  • Learning an L2 broadens understanding of other cultures, fostering tolerance toward different ways of acting and thinking.
  • A classic model of bilingualism supports the idea that abilities learned in one language can be perfectly transferred to another. Children develop similar levels in both languages because both are based on the same central cognitive operator.
  • Being bilingual enhances metalinguistic awareness—the capacity of thinking about the language itself, rather than just using it.
  • Bilingual individuals often feel more comfortable with the use of synonyms and ambiguity, recognizing that there are many correct ways to express an idea.
  • Studies show that bilingual children are better at recognizing a grammatically correct sentence, even when the sentence lacks semantic sense, demonstrating a deeper knowledge of language structure.

Cognitive Advantages

Peal and Lambert (1962) studied 10-year-old Canadian children bilingual in English and French. They found that these children had a higher mental capacity than their monolingual classmates in both verbal and nonverbal tests. They deduced that bilingual children:

  • Form concepts more easily.
  • Possess higher mental flexibility.

One of the most important advantages is the improvement of executive control. This is the set of abilities that includes:

  • The ability to concentrate on something while ignoring distractions.
  • The ability to inhibit automatic reactions if they are inconvenient.
  • The ability to keep short-term information.
  • The ability to think about two concepts simultaneously.
  • The ability to solve problems.

Studies have also shown that bilingualism aids in divergent thinking—the ability to generate many creative solutions for a problem, rather than just a single correct one. It appears that having more than one word for a concept, thanks to knowing an L2, helps in the development of creative thinking.

Benefits are not limited to children; they extend to adults. A 2007 study found that dementia is delayed in bilingual persons, possibly because using two languages keeps the brain more active over a longer period of time.

To summarize, being bilingual does not mean having the exact same level in both languages. Bilingualism exists on a spectrum, and there are more bilingual than monolingual people globally. The most common cases involve people who can use and understand an L2 correctly, even if they do not know both perfectly. It is not necessary to master a second language completely to gain benefits, but the better one knows it, the greater the advantages will be.

Early Immersion and the Sensitive Period

Young children have a higher capacity for learning a second language easily and quickly compared to when they are older. This is because, at an early age, their neuronal plasticity is greater. Their brain forms a huge quantity of connections between different neurons during their first years of life, allowing them to learn quickly. Some experts refer to them as “linguistic geniuses” because of this.

The Sensitive Period

The high ability to learn an L2 begins to decline after seven or eight years old. If a person tries to learn a new language after this age, it becomes more difficult to pronounce sounds, learn vocabulary, and use grammatical structures correctly. This is because the sensitive period has passed. After this stage, the learning process is less natural and requires more formal instruction, conscious effort, and the use of explicit rules.

This highlights the importance of exposing children to two languages from a young age. Babies retain the first sounds they hear in their first months, and as time flows, they begin to only retain the most frequent sounds heard at home. Early exposure helps them retain the capacity for recognizing different sounds, which aids in understanding the world and developing a native-like accent. Children who learn an L2 later will often retain traces of their native language accent.

Bilingualism and L1 Development Myths

Concerns about bilingualism affecting L1 development are mostly myths rather than real evidence. The primary myth is that early bilingualism delays linguistic development in children. However, L1 development is generally similar in bilingual and monolingual children.

What happens is that the bilingual child is learning two different linguistic systems simultaneously, each with its own sounds, vocabulary, and grammatical rules. Since this process requires more cognitive activity, it might appear that the bilingual child is progressing slower, but this is temporary, and the process eventually balances out. For instance, the first words in both languages are often spoken at the same age.

It is true that bilingual children may recognize similar-sounding words later than monolingual ones, but this improves over time. We may also observe a smaller vocabulary in one of the languages in 2- to 3-year-old children. However, if we count the total vocabulary the child knows across both languages, their combined vocabulary list is larger than that of a monolingual child. These differences eventually balance, and the L1 level often becomes even higher than that of a monolingual child.

It is possible for children to initially mix grammatical rules from both languages, but they correct this as they spend more time listening to those languages regularly.

Krashen’s Five Hypotheses

Stephen Krashen proposed several influential hypotheses regarding second language acquisition (SLA).

Acquisition vs. Learning Hypothesis

This is Krashen’s most important and well-known hypothesis. It posits two independent systems for developing competence in an L2:

  • Acquisition: The result of learning without being consciously aware, similar to how children learn their L1. To acquire a language, it is essential to communicate by focusing on the message, not on how the message is said.
  • Learning: The result of formal instruction, where the student is aware of the process and learns explicit grammatical rules.

According to Krashen, acquisition is superior to learning for fluency.

Monitor Hypothesis

This explains how learning and acquisition are related. Acquisition allows us to initiate speech, but the learning system acts as a “monitor” or “vigilance” that corrects and edits mistakes. This monitor only works if the student:

  • Has enough time for thinking.
  • Is focused on speaking correctly.
  • Knows the grammatical rule needed in that specific case.

Krashen argues that the monitor should be minimal, used only for correcting minor mistakes, and should not interfere with communication.

Classification of Monitor Users:
  • Over-users: They use the monitor constantly and live correcting themselves.
  • Under-users: They do not use it or do not know the rules.
  • Optimal users: They use it correctly and appropriately.

Personality also plays an important role: Extroverts usually do not use the monitor, while introverts and those lacking confidence tend to use it constantly.

Natural Order Hypothesis

According to this hypothesis, there is a predictable, natural order in which grammatical structures are acquired. While studies are not 100% identical, the general sequence is highly probable. Krashen insists that educators should not follow this order in language lessons if the objective is acquisition.

Input Hypothesis (i+1)

This hypothesis explains how a second language is acquired, focusing entirely on acquisition. Progress occurs when students receive comprehensible input (i+1)—language that they understand but which is slightly higher than their current level (i). For this, the best option is to receive natural communication at school, as not all students have the same level.

Affective Filter Hypothesis

This states that emotions and attitude affect language acquisition. Positive factors that help the process include motivation, high self-confidence, and low anxiety levels. Conversely, children who lack motivation or are anxious activate the Affective Filter, blocking comprehensible input and making learning difficult.

Cummins’ Language Acquisition Framework

BICS and CALP

Cummins differentiates between two types of language proficiency:

  • BICS (Basic Interpersonal Communication Skills): The basic abilities of oral communication needed to listen or talk in a daily, social situation. These are typically acquired within two years.
  • CALP (Cognitive Academic Language Proficiency): Academic competence in the language necessary to work with complex content like history, science, or mathematics. It takes between five and seven years to develop this competence.

A common situation is a child who can communicate perfectly using BICS but is unable to produce or understand academic texts (CALP).

Common Underlying Proficiency (CUP) in Teaching

Cummins emphasizes that children learn abilities in one language that can be used in another; improving one language helps the other. In teaching, it is essential to promote L1 acquisition, advise parents to read extensively in L1, and encourage daily discussion about what they have learned at school in L1.

For example, if a child already understands the concept of “love,” they just need to learn the English word “love.” Conversely, a child who does not understand the concept needs to learn both the meaning and the proper word.

Evaluating Task Difficulty

Cummins created a model for classifying homework difficulties based on the necessary language level and the visual and contextual support students receive. This helps teachers create adapted activities. The model considers two factors:

  • Cognitive Demand: How much mental effort is required.
  • Context: Whether the task has visual or contextual support.

The most difficult level (high cognitive demand, low context) involves concepts hard to relate to real experiences, such as reading a complex text or listening to an academic conference. This type of classwork is difficult for children who have not developed CALP. Teachers should evaluate how difficult a task will be for a non-native student. While starting with easy tasks is helpful, difficulty must be gradually increased daily, offering visual or oral support. The objective is for students to have demanding but accessible tasks in order to develop CALP.

Additive vs. Subtractive Bilingualism

Cummins differentiates two types of bilingualism:

  • Additive Bilingualism: A second language is added without losing the original language and culture.
  • Subtractive Bilingualism: The second language is learned at the expense of losing the first language and culture.

Studies show that children in additive bilingual environments are generally more successful than those in subtractive ones. Teachers should appreciate all present languages and cultures and integrate them into the classroom to show that they are valued equally alongside the target language.

Stages of Second Language Acquisition

Pre-production (0 to 6 months)

This is called the silent period. Students listen, observe, and absorb the language but cannot use it actively. They may try to repeat words or sentences without full comprehension. They have a vocabulary of about 500 words and typically answer with “yes” or “no” or with gestures.

Early Production (6 to 12 months)

Comprehension improves, and students begin to speak. They can answer basic questions and use memorized sentences, even if they do not fully understand the meaning. They primarily use the present tense. Vocabulary improves to about 1,000 words.

Speech Emergence (1 to 3 years)

Oral expression becomes more balanced. The student can follow the general sense of texts and recognize details. They can create short sentences and formulate simple questions. They still make mistakes but are generally understandable. Vocabulary reaches about 3,000 words.

Intermediate Fluency (3 to 5 years)

Language becomes more complex grammatically and lexically. Speaking is more natural, and the student can begin to think in the L2. They understand principal ideas in texts and use longer, more elaborated sentences. Vocabulary reaches about 6,000 words.

Advanced Fluency (5 to 7 years)

The student is similar to a native speaker. They can communicate freely and confidently in social and academic contexts. They may logically still make minor mistakes but possess an advanced level of proficiency.

Module 2: Content and Language Integrated Learning (CLIL)

CLIL stands for Content and Language Integrated Learning. This approach combines the deep learning of subject content with language development, fostering effective bilingual educational strategies. Culture is considered essential because languages are integral to identity.

Models of Bilingual Education

  • Dual Language Immersion: A class that divides the day between two languages (e.g., English and Spanish).
  • Transitional Bilingual Education: Designed to help students adapt to the target language before transitioning fully into mainstream instruction.
  • CLIL: Teaching an entire subject (e.g., History or Science) in a foreign language.

The Four Cs of CLIL

CLIL methodology is structured around four core components:

  1. Content: Activities focused on knowledge and specific abilities from the subject matter.
  2. Communication: Activities focused on practicing the language in real contexts.
  3. Cognition: Activities that develop comprehension and thinking skills.
  4. Culture: Activities that include cultural knowledge and intercultural understanding.

Do Coyle’s Principles of Deep Learning

Do Coyle emphasizes that education must ensure equality in learning. This includes being clear about abilities and content, and promoting deep learning through:

  • Autonomous learning/acquisition.
  • Integration of knowledge.
  • Internalization of lasting and inherent learning.

This type of learning demands time, practice, effort, collaboration, and language use. Teachers must analyze the language required for the subject.

The Language Triptych

The language needed in a CLIL classroom can be categorized into three areas:

  • Language of Learning: Specific vocabulary and terminology students need to prepare for tests or understand core concepts.
  • Language for Learning: Functional vocabulary that acts as a guide or help for students to complete tasks (e.g., “In conclusion,” “Compare and contrast”). This needs to be prepared and transferable.
  • Language Through Learning: Language that students acquire naturally while learning the subject content.

Phil Ball and Backwards Design

Phil Ball suggests that all subjects are language subjects, which is why teachers need to talk less and give more leadership to their students. To achieve this, activities must be adapted using the “Backwards Design” model.

Backwards Design requires starting from the final product and working backward:

  1. Identify the Desired Results: Determine which concepts students need to learn, the procedure for learning them, and the types of language required.
    • WALT (We Are Learning To): A method for designing clear objectives (e.g., “Students will be able to…”).
    • This step also considers different abilities: Cognitive, Intrapersonal (emotions), and Interpersonal (behavior).
    • It utilizes Bloom’s Taxonomy, a classification system for learning objectives.
  2. Determine Acceptable Evidence (Evaluation): Decide what will be evaluated, using clear, observable criteria.
    • WILF (What I’m Looking For): Criteria used for assessment, often detailed in rubrics or other instruments.
    • Determine when assessment will occur: formative (during the process) or summative (final exam).
  3. Plan Learning Experiences: Create a logical sequence of activities using diverse materials. Lessons should start by activating curiosity and prior knowledge, presenting new language, moving to controlled practice, and finishing with free practice.

Key Concepts in CLIL Pedagogy

Cummins Quadrant: Cognitive Demand vs. Context

This model evaluates task difficulty based on two factors:

  • Cognitive Demand: How much the student has to think.
  • Contextual/Visual Support: How much visual or oral support the student receives.

A supported task includes images, gestures, or visual aids. A non-supported activity would be listening without help or reading a complex text. This model is crucial for CLIL because it seeks to balance cognitive challenges while providing enough support, ensuring students acquire both content and language.

Bloom’s Taxonomy: HOTs and LOTs

Bloom’s Taxonomy classifies learning objectives into different levels of complexity:

  • HOTs (Higher Order Thinking Skills): Superior mental abilities such as analyzing, evaluating, and creating.
  • LOTs (Lower Order Thinking Skills): Foundational mental abilities such as remembering, understanding, and applying.

What is Scaffolding?

Scaffolding is an educational strategy in which teachers provide temporary support or help to their students to achieve a higher level of understanding or skill. This support is gradually removed (retired) when the student can perform the task independently. Scaffolding is vital for CLIL because it makes cognitively demanding content accessible to students who are simultaneously learning the language.

Types of CLIL Activities

Effective CLIL classrooms utilize a variety of activities:

  • Project-based learning (applying content knowledge and language skills).
  • Collaborative activities (students work together to solve problems).
  • Discussions and debates (practicing argumentation on specific topics).
  • Role-playing.
  • Interactive experiments.
  • Reading and writing tasks.
  • Multimedia projects.