Stephen D. Krashen is a prominent linguist known for his influential theories on second language acquisition, particularly developed since the 1980s. His five hypotheses—including the affective filter, acquisition-learning, input, monitor, and natural order hypotheses—examine the relationship between subconscious acquisition and conscious learning, emphasizing the importance of comprehensible input and affective factors like motivation and anxiety. Krashen's work has significant implications for ESL teaching practices, focusing on meaningful interactions and reducing barriers to language learning.

1. Stephen D Krashen
Second Language Acquisition
Dr. Nikhitha Raju

2. Stephen D Krashen(1941-)
• Linguist, educational researcher and political
activist.
• Expert in the field of linguistic, especially in the
theories of language acquisition and development.
• His theory of second language acquisition had
created a large impact in the facet of second
language research and teaching since1980s.

3. Theory of Second Language Acquisition
His five Hypotheses:
Affective
Filter
Hypothesis
Acquisition-
Learning
Hypothesis
Input
Hypothesis
Monitor
Hypothesis
Natural
Order
hypothesis

4. Acquisition v/s Learning
• Two different ways of developing skills in a second language:
Acquisition
Learning

5. Acquisition-learning Hypothesis
Acquisition Learning
 Subconscious process
 Identical to L1 acquisition
 Emphasis given to
meaning
 Conscious Process
 Knowing about a
Language
 Emphasis given to rule

6. Input Hypothesis
• Meaningful output only possible when we get
valuable input.
• According to Krashen, comprehensible input is
one of the most effective thing for language
acquisition.
• By comprehensible input Krashen meant that
one level beyond the level of current
competence.
• Acquisition must be possible when a person
gets more target language atmosphere.

7. Input Hypothesis
Variety of Input
Comprehensible
Input (One level
beyond the level
of present
competence )
Better
Acquisitio
n

8. Affective Filter Hypothesis
• This hypothesis states how affective factors relate to the second
language acquisition process.
• Three categories of Affective factors are mostly related to Second
Language Acquisition (SLA).
 Motivation
 Self-confidence
 Anxiety

9. Affective Filter Hypothesis

10.  High level of
Anxiety

11.  Lack of Motivation

12.  Lack of Self-confidence

13. Monitor Hypothesis
• Acquisition initiates our utterance in a second language.
• Learning has only one function, and that is as a Monitor or editor.
• This monitoring can happen before or after we speak or write(Self-
correction).
• This hypothesis implies that conscious learning plays a limited role in
second language performance.
• There are three conditions must be fulfilled to activate the monitor
system; such as time, focus on form and sufficient knowledge of the
rules.

14. Monitor Hypothesis

15. Monitor Hypothesis
• Highly monitors/over-users
• Moderate monitors/optimal-users
• Low monitors/under-users

16. Monitor Hypothesis
• High monitors are usually monitoring their own output. As a result,
such performers may speak hesitantly, often self-correct in the Middle
of Utterance so they cannot speak with any real fluency
• Low monitors are not ready to use their conscious Knowledge. Low
monitors are uninfluenced by error correction.
• Moderate monitors use the monitor when it is appropriate and when
it does not interfere with communication. They are not use grammar in
ordinary conversation., where it might interfere.

17. Natural Order Hypothesis
• Natural order of acquiring grammar of target
language was another idea given by Krashen.
A natural sequence of a grammar acquisition is
possible. According to Krashen, sometimes a
person acquire the present tense form of the
verb (ing) rather than possessive case.
Copula
Plural
ing form
Article
Auxiliary
I. Past
Possessive
III. Singular
R. Past

18. Feasibility of Krashen’s SLA Theory on ESL
Classroom
Theory into practice:
Input Hypothesis
Affective Filter Hypothesis