Studying Krashen: Benny Lewis and the 5 Theories


Studying Krashen: Benny Lewis and the 5 Theories

Dr. Stephen Krashen has done so much for the teaching and learning of languages through the research and publication of his five theories of language acquisition.

Studying Krashen’s 5 Theories

Krashen’s theory of second language acquisition consists of five main hypotheses:

  • the Acquisition-Learning hypothesis;
  • the Monitor hypothesis;
  • the Natural Order hypothesis;
  • the Input hypothesis;
  • and the Affective Filter hypothesis.

Here’s my cheat sheet of Krashen’s theories:


Acquisition is natural. Learning is intentional and more artificial. Think about the way you learned your own language as a child. You were immersed in messages. You were read to. You watched television. You listened to songs. You read. 

With learning, think about some of the formal instruction you had in school. For example, what a noun is or what an adverb is. Instruction on parts of speech and grammar exercises are examples of formal language instruction that many of us have experienced.


This is the practical result of the language learned. It discusses how learners monitor what they have learned and acquired in the new language.

For example, some over-monitor and as a result, are overly measured in their language use, ultimately at the expense of communication. Some under-monitor, at the expense of accuracy. Optimal learners remain aware enough to monitor their use enough to allow for continued progress yet don’t let mistakes halt their progress.

Natural Order

As Krashen says, “For a given language, some grammatical structures tend to be acquired early, while others late.”

I like to use the example of children again. Think about some of the simple things they say when they’re first learning to speak. They’re choppy and rough. Think about by the time someone graduates from college how sophisticated and polished their language is relative to a small child, and the ease of expression they have. While this natural order seems to be similar among languages and learner profiles, grammar does not need to be learned in a specific sequence.


In order to keep your skills growing in a language, you need comprehensible input. This is language that you can understand, with some new things in there that let you problem solve, think and acquire new structures. They allow you to work on language that is slightly more difficult-just slightly above your level of language- into what you already know.

Affective Filter

This can have a huge impact on how quickly you learn languages. Learning languages can be pretty scary.

Do you have an outgoing personality? Are you an extrovert? Are you willing to put yourself out there, or are you a perfectionist, measured with your communication? 

In order to really bring these theories to life, I’d like to share with you the story of Benny Lewis from Fluent in 3 Months. Benny’s better known as the Irish Polyglot. 

Benny’s a smart guy. He studied engineering at university. He really wanted to learn new languages. But despite his intellect and his strong work ethic, he wasn’t successful in traditional classes. Fast forward about 15 years, and Benny is fluent in more and more languages all the time. 
Without having any background in languages, he perfectly executed Krashen’s five hypotheses. Visit his website, Fluent in 3 Months, as well as his YouTube channel, where he’s documented his journey of language learning missions over the years.

Listen to the episode to hear my study of Benny and Krashen’s 5 Theories.

Krashen, Stephen. “Stephen Krashen’s Theory of Second Language Acquisition.” Stephen Krashen’s Theory of Second Language Acquisition, Stephen Krashen, 3 July 2019,

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