Stephen D. Krashen (born May 14, 1941) is an American linguist, educational researcher, and activist whose work has had a profound influence on second language acquisition (SLA), bilingual education, and language teaching methodologies. Best known for his Input Hypothesis and the Monitor Model, Krashen reshaped how researchers, teachers, and policymakers approach language learning, advocating for comprehensible input and low-stress environments that foster natural acquisition.
Early Life and Education
Stephen Krashen was born in Chicago, Illinois, in 1941. He showed an early interest in languages and education, which later shaped his academic path.
He earned his B.A. in Linguistics from the University of Illinois in 1963, followed by an M.A. in Linguistics from Columbia University in 1964. In 1972, he received his Ph.D. in Linguistics from the University of California, Los Angeles (UCLA).
During his graduate studies, Krashen became interested in second language acquisition and bilingual education, areas that would define his academic career.
Academic Career
After completing his doctorate, Krashen began teaching at several universities before joining the University of Southern California (USC), where he became a professor in the Rossier School of Education.
Throughout his career, he has published over 500 papers and books on topics such as bilingual education, second language acquisition, literacy development, and educational policy. He also became a prominent advocate for free voluntary reading (FVR) and language immersion programs.
Key Contributions to Language Learning
Stephen Krashen’s theories form the backbone of much modern research in second language acquisition. His ideas emphasize that language learning is not just about memorization or grammar drills but about meaningful communication and natural exposure to language.
1. The Monitor Model
Krashen’s most influential framework, the Monitor Model, consists of five hypotheses that explain how people acquire a second language:
| Hypothesis | Core Idea |
|---|---|
| Acquisition-Learning Hypothesis | There are two ways to develop language competence: acquisition (subconscious, natural process) and learning (conscious knowledge of rules). Acquisition is far more important. |
| Monitor Hypothesis | Learned knowledge acts only as a monitor or editor; it can refine output but cannot generate fluency. |
| Input Hypothesis | Language is acquired when learners are exposed to comprehensible input slightly above their current level — known as i+1. |
| Natural Order Hypothesis | Grammatical structures are acquired in a predictable sequence, regardless of teaching order. |
| Affective Filter Hypothesis | Emotional factors like anxiety, motivation, and confidence affect acquisition. A low-stress environment improves learning. |
These five hypotheses collectively argue that language acquisition is most successful when learners are immersed in meaningful, comprehensible input rather than focusing on explicit grammar instruction.
2. Comprehensible Input
Krashen popularized the idea that input — hearing or reading language that is understandable but slightly above the learner’s current ability — is the driving force of language acquisition.
For example:
- Beginners benefit from graded readers, simplified speech, and visuals.
- As learners progress, exposure to authentic materials like books, movies, and conversations helps push their competence forward.
This concept revolutionized language teaching methodologies, moving away from rote memorization and drills toward input-rich environments.
3. Free Voluntary Reading (FVR)
Krashen strongly advocates for extensive reading as a tool for acquiring vocabulary, grammar, and overall fluency. His research shows that learners who read for pleasure:
- Acquire language faster
- Develop better writing skills
- Achieve larger vocabularies
This approach influenced modern reading-based teaching methods and supports the inclusion of graded readers and authentic literature in classrooms.
4. Influence on Bilingual Education
Krashen has been a major advocate for bilingual education in the United States. He argues that:
- Learners acquire second languages faster and better when their first language is supported.
- Immersion combined with comprehensible input leads to higher proficiency.
His research has influenced policies around dual-language programs and English language learner (ELL) education.
Impact on Language Teaching
Krashen’s theories have had lasting effects on language teaching methodologies:
- Inspired Communicative Language Teaching (CLT), which prioritizes real-life communication over grammar drills.
- Influenced content-based instruction and task-based learning, where students acquire language through meaning.
- Provided a theoretical foundation for input-focused approaches, including:
- Extensive reading programs
- Using authentic materials
- Multimedia-based immersion
Modern methods like the Natural Approach (developed with Tracy Terrell) also build directly on Krashen’s principles.
Selected Major Works
- Principles and Practice in Second Language Acquisition (1982)
- The Input Hypothesis: Issues and Implications (1985)
- Second Language Acquisition and Second Language Learning (1988)
- The Power of Reading: Insights from the Research (2004)
- Explorations in Language Acquisition and Use (2003)
Legacy and Influence
Stephen Krashen’s work continues to shape:
- Second Language Acquisition research
- Language teaching methodologies
- Bilingual education policies
- Approaches to literacy and reading programs
By emphasizing comprehensible input and the role of affective factors in learning, Krashen helped shift language education toward a more natural, communicative, and learner-centered model.
References
- Krashen, S. D. (1982). Principles and Practice in Second Language Acquisition. Pergamon Press.
- Krashen, S. D. (1985). The Input Hypothesis: Issues and Implications. Longman.
- Krashen, S. D. (2004). The Power of Reading: Insights from the Research. Heinemann.
- Krashen, S. D., & Terrell, T. D. (1983). The Natural Approach: Language Acquisition in the Classroom. Pergamon.
- Ellis, R. (1997). Second Language Acquisition. Oxford University Press.
- Lightbown, P. M., & Spada, N. (2013). How Languages Are Learned. Oxford University Press.