Input

Input is the language data that learners are exposed to -- everything they hear, read, or otherwise encounter in the target language. It is the raw material of acquisition and arguably the single most important factor in SLA. No theory of second language acquisition denies the necessity of input; the debate is about what kind of input matters, how much is needed, and whether input alone is sufficient.

Input vs Intake

The critical distinction, introduced by Corder (1967), is between input and intake:

• Input = all target language data available in the learner's environment
• Intake = the subset of input that the learner actually processes and incorporates into their developing system (interlanguage)

Not all input becomes intake. The gap between the two is shaped by attention, noticing, developmental readiness, and processing capacity. Gass and Selinker (1994) proposed a five-stage model: apperceived input, comprehended input, intake, integration, and output -- each stage filtering what ultimately becomes acquired knowledge.

Types of Input

By modality:

• Spoken input -- Teacher talk, peer interaction, audio/video, conversation
• Written input -- Texts, instructions, digital media, realia

By authenticity:

• Authentic input -- Language produced for real communicative purposes, not designed for learners (news articles, podcasts, films)
• Modified/simplified input -- Language adjusted for learner level through slower speech, shorter sentences, controlled vocabulary, or glossing

By design:

• Unenhanced input -- Presented without deliberate manipulation of target features
• Enhanced input -- Target features made more salient through Input Enhancement techniques (bolding, underlining, input flooding)
• Input flood -- High-frequency exposure to a target form within meaning-focused material without explicit attention drawn to it

Theoretical Perspectives on Input

• Input Hypothesis (Krashen, 1985) -- Acquisition occurs when learners receive comprehensible input at i+1 (slightly beyond current competence). Input is both necessary and sufficient; output plays no causal role.
• Interaction Hypothesis (Long, 1983, 1996) -- Input is necessary but becomes most useful when learners negotiate meaning during interaction. Negotiation creates modified input tailored to the learner's level.
• Output Hypothesis (Swain, 1985, 1995) -- Input alone is insufficient. Producing output forces learners to process language at a deeper level, notice gaps in their knowledge, and test hypotheses.
• Input Processing (VanPatten, 1996, 2004) -- Focuses on the strategies learners use to connect form and meaning during comprehension. Processing instruction redesigns input to push learners away from default (often inefficient) processing strategies.
• Noticing Hypothesis (Schmidt, 1990) -- Input only becomes intake when learners consciously notice features. This bridges the input-intake gap and provides the rationale for Input Enhancement and Focus on Form.

Quality vs Quantity

Both matter, but quality is more consequential for classroom contexts where time is limited:

• Rich input contains diverse examples of target forms in meaningful contexts
• Compelling input (Krashen's later term) is so interesting that learners forget they are encountering a foreign language
• Frequent input increases the probability that target forms will be noticed and processed
• Varied input from multiple sources and registers builds more robust representations

Classroom Implications

Making input work harder in the classroom:

• Give learners a compelling reason to process input (tasks, information gaps, genuine questions)
• Use visuals, body language, synonyms, and examples to make input comprehensible without oversimplifying
• Combine authentic and modified input: authentic for exposure, modified for focused practice
• Enhance target features in written input through typographical manipulation
• Ensure sufficient exposure time -- input-poor classrooms produce input-poor learners

Related Concepts

Input is the starting point for nearly every SLA theory. It connects to Comprehensible Input and the Input Hypothesis as Krashen's framing, to Input Enhancement and Input Processing as techniques for optimising how input is delivered and processed, to the Output Hypothesis and Interaction Hypothesis as theories that argue input alone is not enough, and to the Noticing Hypothesis as the cognitive mechanism bridging input and intake.