Stephen Krashen is a well-known applied linguist whose work has significantly impacted second language education. He proposed five main hypotheses: 1) the Acquisition-Learning Hypothesis distinguishes natural language acquisition from formal instruction, 2) the Monitor Hypothesis describes the limited role of conscious learning in editing language use, 3) the Natural Order Hypothesis claims the acquisition of language follows a predictable order regardless of learner factors, 4) the Input Hypothesis states that acquisition occurs best through comprehensible input just beyond a learner's level, and 5) the Affective Filter Hypothesis posits that affective variables like motivation and anxiety impact a learner's ability to acquire a new language.

1. Stephen Krashen
D. Fleming
University of Ottawa

2. Stephen Krashen is one of the best known
applied linguists today
has been severely (and often justifiably) criticized
for being pseudo-scientific and simplistic
his legacy has been important if only for the way
he forced the field to deal with some fundamental
issues and contradictions
second language education can not be fully
understood unless one has a grasp on how the
field has tried to deal with his hypotheses.

3. Acquisition/ Learning Hypothesis
Acquisition
the subconscious process involved in using
language automatically in meaningful
communication;
exemplified by children’s use of language;
instilled by meaningful and natural interaction;
speakers not worried about accuracy.
Learning
the conscious processes involved in learning the
grammar and structure of a language;
instilled by decontextualised formal instruction that
usually has limited meaning or usefulness;
far less important than acquisition and separate
from it.

4. Monitor Hypothesis
language learners monitor themselves in terms of
how closely they conform to learnt models of the
target language they have learnt;
this is the limited role of the ‘learning system’;
the 'monitor' is the editor, which plans and
corrects target language use whenever the learner
has:
sufficient time to activate it;
the opportunity to focus on accuracy;
a correct understanding of the correct structural
rules involved.
the role of conscious learning should be limited to
correcting minor errors

5. some learners over use the monitor, which leads
them to excessively concentrate on grammatical
accuracy and neglect fluency;
these learners might be able to provide a
compendium of grammar rules, but can not use the
language for meaningful communication; they are
often introverts, those with low self-confidence and
perfectionists;
other learners under use the monitor, leading them
to be verbose but inaccurate speakers of the second
language; extroverts and non-perfectionists are
under-users;
optimal users have a balanced use of the monitor.

6. Natural Order Hypothesis
Krashen contended, based on research done in
the 1970’s by Dulay & Burt, Fathman and Makino,
that the acquisition of a second language followed
a predictable 'natural order‘, regardless of age,
gender or other background factors;
He noted that these ‘natural orders’ did not
conform to structural or logical descriptions of
grammar;
Ellis (1985) notes that subsequent research has
only partially borne Krashen out. Some patterns do
occur, but great differences exist between first and
second language acquisition that seem to be
functions, at least, of age and economic
circumstances. Ellis makes the distinction between
order and sequence.

7. Input Hypothesis
acquisition best occurs when the learners
receives second language 'input' that is one step
beyond their current stage of linguistic
competence;
often termed as comprehensible input, or 1+
although there are some similarities between
Krashen’s views and Vygotsky’s Zone of Proximal
Development, bear in mind that comprehensible
input occurs in naturalistic settings and
according to a ‘natural order’ of development;
the instructional aspects of Vygotsky’s theory
are not at play here.

8. Affective Filter Hypothesis
'affective variables' (such as motivation, self-
confidence and anxiety) have a large part to play
in determining how receptive one is to learning a
second language;
learners experiencing high motivation, great self-
confidence, and low levels of anxiety acquire the
second language easier; these learners have low
affective filters
learners experiencing low motivation, poor self-
esteem, and high levels of anxiety have high
affective filters.