2.1 Second Language Acquisition Theories, Hypotheses, and Frameworks

2.1 Second Language Acquisition Theories, Hypotheses, and Frameworks

Understanding how individuals acquire a second language (L2) requires examining key theoretical frameworks that have shaped modern English for Speakers of Other Languages (ESOL) pedagogy. Second Language Acquisition (SLA) as an academic discipline synthesizes insights from linguistics, psychology, sociology, and neuroscience. For candidates preparing for the Praxis ESOL (5362) examination, mastering these theoretical models is essential not only for answering explicit conceptual questions but also for making principled instructional decisions in classroom scenarios.

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Historical Foundations: Behaviorism vs. Nativism/Innatism

The formal study of SLA evolved through a major paradigm shift in the mid-twentieth century, moving from external behavioral modification models to internal cognitive and innatist perspectives.

Behaviorist Learning Theory (B.F. Skinner)

During the 1940s and 1950s, Behaviorism dominated educational psychology and language teaching. Grounded in B.F. Skinner's operant conditioning, behaviorists viewed language acquisition as a process of habit formation driven by stimulus-response-reinforcement sequences. Learners were thought to acquire language by imitating environmental models, receiving immediate positive reinforcement for correct utterances, and having incorrect utterances corrected immediately to prevent bad habits.

In the ESOL classroom, behaviorism directly inspired the Audio-Lingual Method (ALM). ALM prioritized oral production through repetitive pattern drills, dialogue memorization, and explicit habituation of target structures. However, behaviorism ultimately proved incapable of explaining key language acquisition phenomena:

• Novel Utterances: Children and L2 learners frequently produce original sentences they have never previously heard or modeled.
• Systematic Errors: Learners systematically produce non-target forms (e.g., "he goed" or "two foots") that could not have resulted from imitating adult speech.

Nativist/Innatist Theory (Noam Chomsky)

In 1959, Noam Chomsky published a landmark critique of Skinner's Verbal Behavior, introducing Nativism (or Innatism). Chomsky argued that human beings are biologically endowed with a specialized mental faculty for language: the Language Acquisition Device (LAD). According to Chomsky, the LAD contains Universal Grammar (UG)—an innate set of abstract linguistic principles and parameters common to all human languages.

Chomsky's fundamental argument rested on the poverty of the stimulus: the language input children receive is often degenerate, incomplete, or ambiguous, yet children effortlessly construct complex, rule-governed grammatical systems in a remarkably short time. Under the Nativist view, language is not acquired through habit formation; rather, innate cognitive structures are triggered and parameterized by exposure to environmental input.

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Krashen's Monitor Model: The Five Core Hypotheses

In the late 1970s and 1980s, Stephen Krashen synthesized nativist concepts into a comprehensive framework specifically tailored to second language acquisition known as the Monitor Model. Krashen's framework remains one of the most influential—and frequently tested—models on the Praxis ESOL examination. The model comprises five distinct, interconnected hypotheses:

                         [ Affective Filter ] (Low = Open / High = Blocked)
                                  │
                                  ▼
[ Comprehensible Input (i+1) ] ──► [ LAD / Acquisition System ] ──► [ Implicit Competence ]
                                                                         │
                                                                         ▼
                                   [ Conscious Learning ] ──────► [ Monitor / Editor ]
                                  (Rules, Formal Study)                  │
                                                                         ▼
                                                                [ Fluent L2 Output ]

1. The Acquisition-Learning Hypothesis

Krashen draws a strict distinction between two independent systems of L2 development:

• Acquisition: A subconscious, natural process identical to how children acquire their first language (L1). It occurs through meaningful interaction in communicative contexts where the focus is on message content rather than linguistic form. Acquisition yields implicit knowledge and drives spontaneous language production.
• Learning: A conscious, formal process involving explicit study of grammatical rules, vocabulary lists, and syntax conventions. Learning yields explicit knowledge stored as conscious facts about language.

Praxis Application: Krashen contends that conscious learning cannot convert directly into subconscious acquisition. True fluency stems exclusively from acquired knowledge.

2. The Monitor Hypothesis

This hypothesis defines the specific operational role of conscious learning. According to Krashen, learned knowledge cannot initiate spontaneous utterances; it functions only as a Monitor or internal editor to alter output produced by the acquired system.

Deploying the Monitor requires three prerequisite conditions:

1. Time: The learner must have sufficient time to retrieve explicit rules.
2. Focus on Form: The learner must be consciously attending to grammatical correctness.
3. Knowledge of the Rule: The learner must know the specific formal rule.

Krashen categorizes learners based on Monitor usage:

• Over-users: Learners who constantly monitor their speech, leading to extreme hesitation, lack of fluency, and fear of speaking.
• Under-users: Learners who rely solely on acquisition, ignoring conscious rules and neglecting formal accuracy.
• Optimal Users: Learners who apply the Monitor judiciously when appropriate (e.g., during written editing or formal presentations) without impeding spontaneous communicative flow.

3. The Natural Order Hypothesis

Krashen asserts that grammatical structures are acquired in a predictable, developmental sequence regardless of the learner's L1 background, age, or sequence of explicit classroom instruction. For example, in English SLA, the progressive -ing and plural -s suffixes are typically acquired well before the third-person singular present tense -s or possessive 's.

Praxis Application: Explicitly teaching a rule out of its natural acquisition order will not force premature acquisition; it only results in temporary learned knowledge accessible via the Monitor.

4. The Comprehensible Input Hypothesis ($i+1$)

This hypothesis posits that language acquisition occurs exclusively when a learner understands input that contains structures slightly beyond their current level of competence. Krashen symbolizes this as $i+1$, where:

• $i$ represents the learner's current stage of interlanguage competence.
• $+1$ represents the next developmental linguistic stage.

Input becomes comprehensible through contextual supports, including visual aids, gestures, body language, simplified teacher speech (teacher talk), graphic organizers, and familiar background knowledge.

5. The Affective Filter Hypothesis

The affective filter is a psychological screen that can block input from reaching the brain's acquisition mechanism (the LAD). Emotional variables affecting the filter include:

• Anxiety: High classroom anxiety raises the filter.
• Self-confidence: Low self-esteem or weak self-efficacy raises the filter.
• Motivation: Low motivation raises the filter.

When the affective filter is high, the learner may understand the message, but the input fails to penetrate the acquisition device. When the filter is low (low anxiety, high self-esteem, strong motivation), input reaches the LAD and acquisition proceeds smoothly.

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Interactionist and Cognitive Frameworks

While Krashen emphasized receptive input, subsequent theorists expanded SLA research by emphasizing interactive communication and active output.

Long's Interaction Hypothesis (Michael Long)

Michael Long extended Krashen's input model by investigating how input becomes comprehensible during face-to-face communication. Long's Interaction Hypothesis asserts that interactive accommodation and negotiation of meaning trigger language acquisition.

When native speakers and L2 learners experience a breakdown in communication, they engage in conversational modifications, including:

• Clarification Requests: Asking the speaker to explain an unclear utterance ("What do you mean by...?").
• Confirmation Checks: Verifying comprehension of the speaker's message ("Are you saying that...?").
• Comprehension Checks: Asking if the interlocutor understood ("Does that make sense?").
• Recasts: Re-stating a learner's incorrect utterance in a corrected form without interrupting communication flow.

Negotiation of meaning forces learners to attend to linguistic form, providing tailored $i+1$ input and pushing them to adjust their own output.

Swain's Output Hypothesis (Merrill Swain)

Merrill Swain challenged Krashen's view that input alone is sufficient for SLA. Studying immersion programs in Canada, Swain observed that students exposed to years of rich comprehensible input achieved high receptive skills but continued to make persistent grammatical errors in production. Swain proposed the Output Hypothesis, arguing that producing language (pushed output) performs three critical functions:

1. Noticing/Triggering Function: Producing L2 forces learners to realize what they want to say vs. what they are capable of saying, drawing attention to gaps in their interlanguage.
2. Hypothesis-Testing Function: Utterances serve as trials where learners test rules and assess listener feedback.
3. Metalinguistic Function: Reflecting on produced language helps internalize linguistic forms and syntactic structures.

Swain emphasized that while input requires semantic processing (focusing on meaning), output pushes learners from semantic to syntactic processing (focusing on grammatical encoding).

Vygotsky's Social Constructivism & Zone of Proximal Development (ZPD)

Grounded in Lev Vygotsky's sociocultural theory, Social Constructivism views language learning as a socially mediated process. Learning occurs first on a social plane (interpsychological) through interaction with More Knowledgeable Others (MKOs), and is subsequently internalized on an individual plane (intrapsychological).

Key constructivist concepts include:

• Zone of Proximal Development (ZPD): The distance between a learner's actual developmental level (what they can perform independently) and their potential developmental level (what they can accomplish with guidance and collaboration).
• Scaffolding: Coined by Wood, Bruner, and Ross (and applied to SLA by Donato), scaffolding represents temporary instructional support structures—such as sentence frames, modeling, graphic organizers, and peer coaching—that allow learners to operate within their ZPD. Scaffolds are systematically faded as the learner gains independent mastery.

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Summary Comparison of SLA Theoretical Frameworks

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Praxis Exam Application & Pedagogical Traps

When evaluating test items on SLA theories, candidates should watch for common conceptual traps:

• Input vs. Output Misconceptions: Remember that Krashen prioritizes input ($i+1$), whereas Swain argues that input alone is insufficient and requires pushed output.
• Corrective Feedback Timing: ALM/Behaviorism advocates instant error correction to break bad habits. Modern communicative approaches view errors as natural indicators of interlanguage development.
• The BICS/CALP and Monitor Trap: Expecting newcomer ELLs to deploy the Monitor during spontaneous speaking is unrealistic; the Monitor requires time and conscious rule retrieval.