The term second language acquisition (SLA) refers to the processes through which someone acquires one or more second or foreign languages. SLA researchers look at acquisition in naturalistic contexts (where learners pick up the language informally through interacting in the language) and in classroom settings. Researchers are interested in both product (the language used by learners at different stages in the acquisition process) and process (the mental process and environmental factors that influence the acquisition process). In this chapter I trace the development of SLA from its origins in contrastive analysis. This is followed by a selective review of research, focusing on product-oriented studies of stages that learners pass through as they acquire another language, as well as investigations into the processes underlying acquisition. The practical implications of research are then discussed, followed by a review of current and future trends and directions.

1. Second language acquisition by
David Nunan
MA English Sem.3, ELT1; Unit 2
Department of English,
Maharaja Krishnakumarsinhji Bhavnagar University

2. Introduction
• The term second language acquisition (SLA) refers to the
processes through which someone acquires one or more
second or foreign languages. SLA researchers look at
acquisition innaturalistic contexts (where learners pick up the
language informally through interacting in the language) and
in classroom settings. Researchers are interested in both
product (the language used by learners at different stages in
the acquisition process) and process (the mental process and
environmental factors that influence the acquisition process).
In this chapter I trace the development of SLA from its origins
in contrastive analysis. This is followed by a selective review
of research, focusing on product-oriented studies of stages
that learners pass through as they acquire another language,
as well as investigations into the processes underlying
acquisition. The practical implications of research are then
discussed, followed by a review of current and future trends
and directions.

3. Background
• The discipline now known as SLA emerged from comparative
studies of similarities and differences between languages.
These studies were conducted in the belief that a learner's
first language (LI) has an important influence on the
acquisition of a second (L2), resulting in the 'contrastive
analysis' (CA) hypothesis. Proponents of contrastive analysis
argued that where LI and L2 rules are in conflict, errors are
likely to occur which are the result of 'interference' between
LI and L2. For example, the hypothesis predicted that Spanish
LI learners would tend, when learning English, to place the
adjective after the noun as is done in Spanish, rather than
before it.
• Such an error can be explained as 'negative transfer' of the LI
rule to the L2. When the rules are similar for both languages,
'positive transfer' would occur, and language learning would
be facilitated. Where a target language feature does not exist
in the LI, learning would also be impeded.

4. • Thus, English LI learners will encounter difficulty
trying to master the use of nominal classifiers in
certain Asian languages such as Cantonese, because
these do not exist in English. In terms of pedagogy,
contrastivists held that learners' difficulties in
learning an L2 could be predicted on the basis of a
systematic comparison of the two languages, and
that learners from different first language
backgrounds would experience different difficulties
when attempting to learn a common L2.

5. • The CA hypothesis was in harmony with the prevailing
psychological theory of the time: behaviourism. Behaviourists
believed that learning was a process of habit formation.
Linguistic habits acquired by individuals as their LI emerged
would have a marked influence on their L2 acquisition. It is
no coincidence that research questioning the contrastivist
position emerged at about the same time as cognitive
psychologists began to challenge behaviourism. A major shift
in perspective occurred in the 1960s, when linguists and
language educators turned their attention from the CA of
languages and began studying the specific language learners
used as they attempted to communicate in the target
language. In an important publication, Corder (1967) made a
strong case for the investigation of learners' errors as a way
of obtaining insights into the processes and strategies
underlying SLA. Errors were seen not as evidence of
pathology on the part of learners (as suggested by
behaviourism), but as a normal and healthy part of the
learning process.

6. • The systematic study of learners' errors revealed
interesting insights into SLA process. First, learners
made errors that were not predicted by the CA
hypothesis. Second, the errors that learners made
were systematic, rather than random. Third,
learners appeared to move through a series of
stages as they developed competence in the target
language. These successive stages were
characterised by particular types of error, and each
stage could be seen as a kind of interlanguage or
'interim language' in its own right (Selinker 1972).

7. • Not surprisingly, the field of SLA has been strongly
influenced by LI acquisition. SLA researchers have
looked to LI acquisition for insights into ways of
investigating the acquisition process as well as the
outcomes of the research. Particularly influential
was a pioneering study by Brown (1973), who
conducted a longitudinal case study of three
children acquiring English as an LI. Brown traced the
development of 14 grammatical structures,
discovering that, contrary to expectations, there
was no relationship between the order in which
items were acquired and the frequency with which
they were used by the parents.

8. Research
• PRODUCT-ORIENTED RESEARCH During the early 1970s a
series of empirical investigations into learner language were
carried out which became known as the 'morpheme order'
studies. Their principal aim was to determine whether there
is a 'natural' sequence in the order in which L2 learners
acquire the grammar of the target language. Dulay and Burt
(1973, 1974) - the principal architects of the morpheme order
studies - found that, like their LI counterparts, children
acquiring an L2 appeared to follow a predetermined order
which could not be accounted for in terms of the frequency
with which learners heard the language items. Moreover,
children from very different LI backgrounds (Spanish and
Chinese) acquired a number of morphemes in virtually the
same order. However, the order differed from that of the LI
learners investigated by Brown. A replication of the studies
with adult learners produced strikingly similar results to
those with children (Bailey et al. 1974).

9. • As a result of these and other investigations, it was
concluded that in neither child nor adult L2
performance could the majority of errors be
attributed to the learners' Lls, and that learners in
fact made many errors in areas of grammar that are
comparable in both the LI and L2, errors which the
CA hypothesis predicted would not occur. Dulay
and Burt (1974) therefore rejected the hypothesis,
proposing instead a hypothesis entitled 'L2
acquisition equals LI acquisition' and indicating that
the two hypotheses predict the appearance of
different types of errors ('goofs') in L2 learners'
speech.

10. • Briefly the CA hypothesis states that while the child
is learning an L2, he [or she] will tend to use his
native language structures in his L2 speech, and
where structures in his LI and his L2 differ he will
goof. For example, in Spanish, subjects are often
dropped, so Spanish children learning English
should tend to say Wants Miss Jones for He wants
Miss Jones.

11. • The 'L2 acquisition equals LI acquisition' hypothesis
holds that children actively organize the L2 speech
that they hear and make generalizations about its
structure as children learning their LI do. Therefore
the goofs expected in any particular L2 production
would be similar to those made by children learning
the same language as their LI. For example Jose
want Miss Jones would be expected since LI
acquisition studies have shown that children
generally omit functors, in this case the -s inflection
for third person singular present indicative. (Dulay
and Burt 1974: 96)

12. • The morpheme order studies indicated a predetermined
order of acquisition for certain grammatical morphemes.
Subsequent research also showed that this order could not
be changed by instruction. However, the researchers were
unable to explain why certain items were acquired before
others. During the 1980s, however, a number of researchers
studying the acquisition of German and English proposed an
interested explanation for the disparity between instruction
and acquisition based on speech-processing constraints
(Pienemann 1989). They argued that grammatical items can
be sequenced into a series of stages, each more complex
than the last. However, this complexity is determined by the
demands made on short-term memory, rather than by the
conceptual complexity of the items in question. Take, e.g.,
third person -s, which morpheme studies had shown is
acquired late. These researchers could explain why this was
so. According to pedagogical grammars, the item is relatively
straightforward. If the subject of a sentence is singular, add -s
to the main verb.

13. • In the 1980s Stephen Krashen was the best-known figure in the
SLA field. He formulated a controversial hypothesis to explain the
disparity between the order in which grammatical items were
taught and the order in which they were acquired, arguing that
there are two mental processes operating in SLA: conscious
learning and subconscious acquisition. Conscious learning focuses
on grammatical rules, enabling the learner to memorise rules and
to identify instances of rule violation. Subconscious acquisition is a
very different process, facilitating the acquisition of rules at a
subconscious level. According to Krashen (1982, 1988), when using
the language to communicate meaning, the learner must draw on
subconscious knowledge. The suggestion of conscious and
subconscious processes functioning in language development was
not new or radical; however, Krashen's assertion that these
processes were totally separate, i.e. that learning could not
become acquisition, was. Krashen went on to argue that the basic
mechanism underlying language acquisition was comprehension.
According to his comprehensible input hypothesis, when the
student understands a message in the language containing a
structure, his or her current level of competence advances by one
step, and that structure is acquired. These hypotheses had a
marked influence on practice, as outlined below.

14. • PROCESS-ORIENTED RESEARCH Research reviewed
above focused on the products or outcomes of
acquisition. A growing body of research considers
learning processes, exploring the kinds of classroom
tasks that appear to facilitate SLA. The bulk of this
research focuses on activities or procedures which
learners perform in relation to the input data. Given
the extent of research in the field, this review is
necessarily selective. In the first of a series of
investigations into learner-learner interaction, Long
(1981) found that two-way tasks (in which all students
in a group discussion had unique information to
contribute) stimulated significantly more modified
interactions than one-way tasks (in which one member
of the group possessed all the relevant information).

15. • Similarly, Doughty and Pica (1986) found that required
information-exchange tasks generated significantly more
modified interaction than tasks where exchange of information
was optional. The term 'modified interaction' refers to
instances during an interaction when the speaker alters the
form in which his or her language is encoded to make it more
comprehensible. Such modification may be prompted by lack of
comprehension on the listener's part. (For further details, see
Chapter 25 on task-based learning.) This research into modified
interaction was strongly influenced by Krashen's hypothesis
that comprehensible input was a necessary and sufficient
condition for SLA, i.e. that acquisition would occur when
learners understood messages in the target language. Long
(1985a: 378) advanced the following arguments (which are
paraphrased) in favour of tasks which promote conversational
adjustments or interactional modifications on the part of the
learner:

16. • Where (a) is linguistic/conversational adjustment,
(b) is comprehensible input and (c) is acquisition:
Step 1: show that (a) promotes (b). Step 2: show
that (b) promotes (c). Step 3: deduce that (a)
promotes (c). Satisfactory evidence of the (a) -> (b)
-> (c) progression would allow the linguistic
environment to be posited as an indirect causal
variable in SLA. (The relationship would be indirect
because of the intervening 'comprehension'
variable.)
• In a relatively short period of time, SLA researchers
have generated an impressive number of empirical
studies. For detailed reviews of other studies and
issues, see Larsen-Freeman and Long 1991; R.Ellis
1994.

17. Practice
• In this section, practical pedagogical implications of the conceptual and
empirical work summarised above are presented and exemplified. I focus
particularly on claims made by SLA researchers for product-oriented
syllabuses, the implications of the comprehensible input hypothesis, and
proposals for task-based language teaching. Krashen's work on the
subconscious acquisition hypothesis and the comprehensible input
hypothesis is summarised above. According to these hypotheses, innate
processes guide SLA. In practical terms, researchers argued that learners
should be provided with much natural input, especially extensive listening
opportunities and particularly in the early stages of learning. They also argue
that a silent phase at the beginning of language learning (when the student is
not required to produce the new language) has proven useful for most
students in reducing interlingual errors and enhancing pronunciation. Finally,
and most controversially, they argued that formal grammar instruction was
of limited utility as it fuelled conscious learning rather than subconscious
acquisition (Dulay et al. 1982; Krashen and Terrell 1983). While relatively few
researchers still subscribe to Krashen's hypotheses, at least in their original
form, the value of rich and varied listening input early on has wide support
(for more details, see Chapter 1).

18. • Krashen's comprehensible input hypothesis was
challenged by Swain (1985), who investigated
immersion programmes in Canada in which children
receive content instruction in a language other than
their LI. Native speakers of English receive instruction
in maths, science, etc. in French, and vice versa for
French native speakers. These children therefore
receive massive amounts of comprehensible input.
Despite this, L2 development is not as advanced as it
should be according to the comprehensible input
hypothesis. Swain found that the basic instructional
pattern in class was one in which teachers talked a
great deal and students got to say very little. Based on
her observations, Swain formulated an alternative
hypothesis - the 'comprehensible output' hypothesis -
suggesting that opportunities to produce language
were important for acquisition.

19. • The idea that grammatically sequenced syllabuses and the conscious
learning of grammar were of limited utility in language learning was also
vigorously rejected by proponents of the teachability hypothesis. In their
view, grammatical structures can be classified according to the demands
they make on the learner's working memory. The greater the demands, the
more difficult the structure is to learn. An item will only be acquired, and
therefore should only be taught, when the learner is developmentally ready
to acquire it. The researchers who formulated this hypothesis argued that
grammar could and should be taught, but that the timing of instruction
should be in accord with the learner's developmental stage.
• The process-oriented research work of Long and others provided impetus
for the development of task-based language teaching. In task-based
language teaching, the start point for designing language courses is not an
ordered list of linguistic items, but a collection of tasks. SLA research has
informed the work of syllabus designers, methodologists and materials
writers by suggesting that tasks encouraging learners to negotiate meaning
are healthy for acquisition. The growing importance of 'task' as a
fundamental element in curriculums and textbooks of all kinds underlines
the growing links between process-oriented research and classroom
pedagogy.

20. Current and future trends and directions
• Current SLA research orientations can be captured by a single
word: complexity. Researchers have begun to realise that there
are social and interpersonal as well as psychological dimensions to
acquisition, that input and output are both important, that form
and meaning are ultimately inseparable, and that acquisition is an
organic rather than linear process. In a recent study, Martyn
(1996) investigated the influence of certain task characteristics on
the negotiation of meaning in small group work, looking at the
following variables:
– interaction relationship: whether one person holds all of the
information required to complete the task, whether each participant
holds a portion of the information, or whether the information is
shared;
– interaction requirement: whether or not the information must be
shared;
– goal orientation: whether the task goal is convergent or divergent;
– outcome options: whether there is only a single correct outcome, or
whether more than one outcome is possible.

21. • The results seem to indicate that while task variables appear
to have an effect on the amount of negotiation for meaning,
there appears to be an interaction between task variables,
personality factors and interactional dynamic. This ongoing
research underlines the complexity of the learning
environment, and the difficulty of isolating psychological and
linguistic factors from social and interpersonal ones. A major
challenge for curriculum designers, materials writers and
classroom practitioners who subscribe to task-based teaching
is how to develop programmes that integrate tasks with
form-focused instruction. This is particularly challenging
when teaching beginners in foreign language contexts. A
number of applied linguists (see, e.g., R. Ellis 1995) are
currently exploring the extent to which one can implement
task-based teaching with beginner learners, and experiments
are under way to establish the appropriate balance and 'mix'
between tasks which have non-linguistic outcomes and
exercises which have linguistic outcomes.

22. • In searching for metaphors to reflect the complexity
of the acquisition process, some researchers have
argued that the adoption of an 'organic' perspective
can greatly enrich our understanding of language
acquisition and use. Without such a perspective,
our understanding of other dimensions of language
(such as the notion of 'grammaticality') will be
piecemeal and incomplete, as will any attempt at
understanding and interpreting utterances in
isolation from the contexts in which they occur. The
organic metaphor sees SLA more like growing a
garden than building a wall.

23. • From such a perspective, learners do not learn one
thing perfectly one item at a time, but learn
numerous things simultaneously (and imperfectly).
The linguistic flowers do not all appear at the same
time, nor do they all grow at the same rate. Some
even appear to wilt for a time before renewing their
growth. Rate and speed of development are
determined by a complex interplay of factors
related to pedagogical interventions (Pica 1985);
speech-processing constraints (Pienemann and
Johnston 1987); acquisitional processes (Pienemann
1989); and the influence of the discoursal
environment in which the items occur (Levinson
1983; McCarthy 1991; Nunan 1993, 1999).

24. Conclusion
• In this chapter, I describe the emergence of SLA as a
discipline from early work in CA, error analysis and
interlanguage development. I examine research into
SLA in both naturalistic and instructional settings,
considering both process- and product-oriented
studies. The chapter also looks at the practical
implications of current research for syllabus design and
methodology, focusing in particular on the implications
of SLA research for syllabus design, the input
hypothesis, and task-based language teaching. The final
part of the chapter suggests that future work will
attempt to capture the complexity of the acquisition
process by incorporating a wide range of linguistic,
social, interpersonal and psycholinguistic variables into
the design of the research process.

25. Key readings
• R. Ellis (1994) The Study of Second Language
Acquisition
• Krashen (1982) Principles and Practice in Second
Language Acquisition
• Larsen-Freeman (1991) Second language acquisition
research: Staking out the territory
• Larsen-Freeman and Long (1991) An Introduction to
Second Language Acquisition Research
• Lightbrown and Spada (1993) How Languages are
Learned
• Nunan (1999) Second Language Teaching and Learning