A primer on language inputUpdated 2026-11-09
What Is Comprehensible Input? Try Jibber Jabber
Menu

Comprehensible input · Primer

Research on comprehensible input

Research supports several routes for language learning, including meaningful reading and instruction. It does not establish that understandable input alone is sufficient for every learner or skill.

By Jibber Jabber · Updated

On this page (4)

Theory is not a test result

Krashen's 1982 book states a theory of acquisition. It is a primary source for his claims, not a controlled comparison that proves the input-only claim. A study must be read in light of its participants, comparison and outcome measures.

Reading and vocabulary

Hu and Nation studied unknown vocabulary density in reading; Kremmel and colleagues later replicated the work and did not fully confirm the original threshold. Neither study establishes a universal percentage for video or a rule that applies to every reader.

Instruction and interaction

Norris and Ortega's research synthesis examines the effects of second-language instruction. Long's account discusses interaction, and Swain's work argues for a role for output. These perspectives do not all make the same claims or test the same activities.

Use evidence with care

Ask what was measured and what the comparison group did. Better performance on a particular reading test does not prove that a video app produces the same result. No source on this site establishes a fixed number of hours to fluency.

Sources

  1. Hu and Nation (2000), unknown vocabulary density and reading comprehension
  2. Kremmel and colleagues (2023), replication of Hu and Nation
  3. Norris and Ortega (2000), synthesis of second-language instruction
  4. Krashen (1982), Principles and Practice in Second Language Acquisition
  5. Long (1996), the linguistic environment in second language acquisition
  6. Swain (1985), publication details in the reference list of a Cambridge article

Continue reading

Cite this page

Jibber Jabber. "Research on comprehensible input." What Is Comprehensible Input?, updated 2026-11-09. https://whatiscomprehensibleinput.com/research/

How the related sites connect

This guide is one of a collection published by Jibber Jabber. The sites share one publisher and are not independent endorsements. See the related websites.