IMPLICIT AND EXPLICIT
CORRECTIVE FEEDBACK
AND THE ACQUISITION OF
L2 GRAMMAR
Rod Ellis, Shawn Loewen, and Rosemary Erlam
University of Auckland
This article reviews previous studies of the effects of implicit and
explicit corrective feedback on SLA, pointing out a number of meth-
odological problems. It then reports on a new study of the effects of
these two types of corrective feedback on the acquisition of past tense
-ed. In an experimental design (two experimental groups and a con-
trol group), low-intermediate learners of second language English
completed two communicative tasks during which they received either
recasts (implicit feedback) or metalinguistic explanation (explicit feed-
back) in response to any utterance that contained an error in the tar-
get structure. Acquisition was measured by means of an oral imitation
test (designed to measure implicit knowledge) and both an untimed
grammaticality judgment test and a metalinguistic knowledge test
(both designed to measure explicit knowledge). The tests were admin-
istered prior to the instruction, 1 day after the instruction, and again 2
weeks later. Statistical comparisons of the learners’ performance on
the posttests showed a clear advantage for explicit feedback over
implicit feedback for both the delayed imitation and grammaticality
judgment posttests. Thus, the results indicate that metalinguistic expla-
nation benefited implicit as well as explicit knowledge and point to
the importance of including measures of both types of knowledge in
experimental studies.
This research was funded by a Marsden Fund grant awarded by the Royal Society of Arts of New
Zealand+ Researchers other than the authors who contributed to the research were Jenefer Philip,
Satomi Mizutami, Keiko Sakui, and Thomas Delaney+ Thanks go to the editors of this special issue
and to two anonymous SSLA reviewers of a draft of the article for their constructive comments+
Address correspondence to: Rod Ellis, Department of Applied Language Studies and Linguistics,
University of Auckland, Private Bag 92019, Auckland, New Zealand; e-mail: r+ellis@auckland+ac+nz+
SSLA, 28, 339–368+ Printed in the United States of America+
DOI: 10+10170S0272263106060141
© 2006 Cambridge University Press 0272-2631006 $12+00 339
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Corrective feedback takes the form of responses to learner utterances that
contain an error+ The responses can consist of ~a! an indication that an error
has been committed, ~b! provision of the correct target language form, or
~c! metalinguistic information about the nature of the error, or any combina-
tion of these+
There has been a growing interest in the role of corrective feedback in SLA
in the last decade+ A number of descriptive studies based on data collected in
classrooms ~e+g+, Panova & Lyster, 2002; Sheen, 2004! and on data collected in
a laboratory-type setting ~e+g+, Iwashita, 2003; Mackey, Oliver, & Leeman, 2003;
Philp, 2003! have examined the types of corrective feedback received by learn-
ers and the extent to which this feedback is noticed, or uptaken, or both by
the learners+ Experimental studies have attempted to examine the contribu-
tion that corrective feedback makes to acquisition ~e+g+, Ayoun, 2004; Han, 2002;
Leeman, 2003; Lyster, 2004!+ This research has addressed, among other issues,
the relative efficacy of implicit and explicit types of corrective feedback+
THEORETICAL ISSUES
A distinction can be drawn between implicit0explicit learning and implicit0
explicit knowledge+ In the case of learning, the term implicit refers to “acqui-
sition of knowledge about the underlying structure of a complex stimulus
environment by a process that takes place naturally, simply and without con-
scious operations,” whereas explicit learning is “a more conscious operation
where the individual makes and tests hypotheses in search for a structure”
~N+ Ellis, 1994, p+ 2!+
In the case of knowledge, the term implicit refers to knowledge that learn-
ers are only intuitively aware of and that is easily accessible through auto-
matic processing, whereas explicit knowledge consists of knowledge that
learners are consciously aware of and that is typically only available through
controlled processing+ Explicit knowledge might be linked to metalinguistic
labels+ These two types of knowledge are not mutually exclusive; that is, speak-
ers can hold implicit and explicit representations of the same linguistic fea-
ture, as, for example, in the case of linguists who formulate explicit rules on
the basis of their implicit knowledge of a language+
Schmidt ~1994! stated that “implicit and explicit learning and implicit and
explicit knowledge are related but distinct concepts that need to be sepa-
rated” ~p+ 20!+ It can be argued, for example, that implicit knowledge is not
entirely dependent on implicit learning but can arise as a product of learners
intentionally practicing linguistic forms that they initially know explicitly
~DeKeyser, 2003!+ It has also been argued that the development of implicit learn-
ing involves at least some degree of consciousness, as when learners notice
specific linguistic forms in the input ~Schmidt!+
Corrective feedback differs in terms of how implicit or explicit it is+ In the
case of implicit feedback, there is no overt indicator that an error has been
340 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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committed, whereas in explicit feedback types, there is+ Implicit feedback often
takes the form of recasts, defined by Long ~in press! as
a reformulation of all or part of a learner’s immediately preceding utter-
ance in which one or more non-target like ~lexical, grammatical etc+! items
are replaced by the corresponding target language form~s!, and where,
throughout the exchange, the focus of the interlocutors is on meaning not
language as an object+ ~p+ 2!
Recasts, therefore, provide positive evidence, but, as Nicholas, Lightbown, and
Spada ~2001! noted, it is not clear whether they provide negative evidence, as
learners might have no conscious awareness that the recast is intended to be
corrective+ Explicit feedback can take two forms: ~a! explicit correction, in which
the response clearly indicates that what the learner said was incorrect ~e+g+,
“No, not goed—went”! and thus affords both positive and negative evidence
or ~b! metalinguistic feedback, defined by Lyster and Ranta ~1997! as “com-
ments, information, or questions related to the well-formedness of the learn-
er’s utterance” ~p+ 47!—for example, “You need past tense,” which affords only
negative evidence+
It can also be argued that recasts and explicit corrective strategies differ
in terms of whether they cater to implicit or explicit learning+ For Long ~1996!,
recasts work for acquisition precisely because they are implicit, connecting
linguistic form to meaning in discourse contexts that promote the micropro-
cessing ~i+e+, noticing or rehearsing in short-term memory! required for implicit
language learning+ Doughty ~2001!, building on Long’s rationale for focus-on-
form, argued that recasts constitute the ideal means of achieving an “immedi-
ately contingent focus on form” and afford a “cognitive window” ~p+ 252! in
which learners can rehearse what they have heard and access material from
their interlanguage+ In contrast, explicit corrective feedback strategies, such
as metalinguistic feedback, are more likely to impede the natural flow of com-
munication and to activate the kind of learning mechanisms that result in
explicit rather than implicit second language ~L2! knowledge+ However, such a
view is not unproblematic+
First, it is not certain that all recasts are as implicit as Long ~1996! and
Doughty ~2001! assumed+ Some recasts are quite explicitly corrective+ Indeed,
the kind of corrective recasts that Doughty and Varela ~1998! employed in their
experimental study were remarkably explicit+ They were preceded by a rep-
etition of the learner’s utterance with the erroneous elements highlighted by
emphatic stress+ If the learner did not self-correct, recasts with emphatic stress
to draw attention to the reformulated elements followed+ Thus, if the correc-
tive force of the recast becomes self-evident, it is difficult to argue that it con-
stitutes an implicit or even a relatively implicit technique+ Second, recasts can
only work for acquisition if learners notice the changes that have been made
to their own utterances, and there are reasons to believe that they do not
always do so+ Lyster ~1998! has shown that the levels of repair in uptake fol-
lowing recasts are notably lower than those following more explicit types of
Implicit and Explicit Corrective Feedback 341
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feedback+ The findings from Lyster’s research, which examined immersion
classrooms in Canada, were corroborated by Sheen ~2004!, who found that
repair occurred less frequently following recasts than following explicit cor-
rection and metalinguistic feedback in four different instructional contexts
~immersion, Canadian English as a second language @ESL# , New Zealand ESL,
and Korean English as a foreign language!+ Even though repair cannot be taken
as a measure of learning, it is reasonable to assume that it constitutes a mea-
sure of whether learners have noticed the key linguistic forms ~although notic-
ing can occur even if there is no uptake!+ Further evidence of the difficulty
that learners might experience in attending to the key forms comes from a
study by Mackey, Gass, and McDonough ~2000!, which demonstrated that learn-
ers often failed to perceive recasts that contained morphosyntactic reformu-
lations as corrections+ Finally, we cannot be certain that recasts promote
acquisition of implicit knowledge+ Indeed, it is entirely possible that recasts
result in explicit knowledge, as demonstrated in Long, Inagaki, and Ortega
~1998!; in this study, all eight students who had learned the target structure
~Spanish adverb word order! through recasts were able to explicitly and cor-
rectly formulate an explanation of the rule+ Thus, there are some doubts as to
how effective recasts are in promoting learning as well as to what kind of learn-
ing and knowledge they cater+
A case can also be made for the contribution of corrective strategies that
are self-evidently corrective to learning+ Carroll’s ~2001! autonomous induc-
tion theory posits that feedback can only work for acquisition if the corrective
intentions of the feedback are recognized by the learner+ Additionally, learners
must be able to locate the error; Carroll noted that “most of the indirect forms
of feedback do not locate the error” ~p+ 355!+ Recasts do not overtly signal that
an error has been made and might assist in locating the error depending on
whether the recast is full ~i+e+, the whole erroneous utterance is reformulated!
or partial ~i+e+, only the erroneous part of the utterance is reformulated!, as
Sheen’s ~in press! study indicates+ In contrast, explicit types of feedback not
only make the corrective force clear to the learner but also give clues as to the
exact location of the error+ As such, they might be more likely to induce learn-
ers to carry out the cognitive comparison between their error and the target
form ~R+ Ellis, 1994!, which is believed to foster acquisition ~Schmidt, 1994!+
Connectionist models also lend support to explicit error correction+ N+ C+
Ellis ~2005! distinguished between the mechanisms of conscious and uncon-
scious learning, emphasizing the role of attention and consciousness in the
former and of connectionist learning in the latter+ He proposed the learning
sequence in ~1!+
~1! external scaffolded attention r internally motivated attention r explicit learn-
ingr explicit memoryr implicit learningr implicit memory, automatization, and
abstraction
Ellis went on to suggest that “conscious and unconscious processes are dynam-
ically involved together in every cognitive task and in every learning epi-
342 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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sode” ~p+ 340!+ Although he did not suggest that explicit corrective feedback
is the ideal mechanism for achieving this continuous synergy ~indeed, his
discussion of feedback is restricted to recasts!, it would seem that the meta-
linguistic time-outs from communicating afforded by explicit correction con-
stitute a perfect context for melding the conscious and unconscious processes
involved in learning+Within the context of a single interactional exchange, such
a time-out creates an opportunity for learners to traverse the learning sequence
sketched out in ~1!+ Of course, no single exchange can guarantee that the tar-
geted form will enter implicit memory, but repeated exchanges—directed at
the same linguistic form—might be expected to do so+ Thus, according to such
a theoretical perspective, explicit corrective feedback caters not just to explicit
learning and explicit memory but also to implicit learning and implicit memory+
PREVIOUS RESEARCH ON CORRECTIVE FEEDBACK
This review will focus on studies that have compared the effects of implicit
and explicit corrective feedback on L2 acquisition and will address, in par-
ticular, methodological issues in keeping with the theme of this special issue+1
There have been a number of other studies that investigated separately
whether either implicit or explicit corrective feedback facilitates acquisition+
Nicholas et al+ ~2001!, Long ~in press!, and Ellis and Sheen ~in press! pro-
vided reviews of the research on recasts+ In general, the recast studies dem-
onstrated that implicit feedback of this kind can have a beneficial effect on
acquisition, especially when the recasts are more explicit in nature ~as in
Doughty & Varela, 1998!+ Other studies demonstrated that explicit feedback
is of value+ Carroll, Roberge, and Swain ~1992!, for example, found that a group
that received explicit corrective feedback directed at two complex French
noun suffixes ~–age and –ment! outperformed a group that received no feed-
back, although no generalization of learning to nouns not presented during
the treatment occurred+ Thus, the recast and explicit feedback studies dem-
onstrated that both types of feedback can be effective+
Table 1 summarizes 11 studies that have compared implicit and explicit
corrective feedback+ It is not easy to come to clear conclusions about what
these studies reveal due to a number of factors+ First, whereas some of the
studies are experimental in nature ~e+g+, Carroll, 2001; Carroll & Swain, 1993;
Lyster, 2004; Rosa & Leow, 2004!, others are not ~e+g+, DeKeyser, 1993; Havranek
& Cesnik, 2003!, as this second group of researchers investigated corrective
feedback through post hoc analyses of normal classroom lessons+ Second, the
studies vary in terms of whether they involved laboratory, classroom, or
computer-based interaction+ Third, the nature of the treatment activities per-
formed by the learners in these studies differed considerably+ In some cases,
the activities involved fairly mechanical exercises ~e+g+, Carroll; Carroll & Swain;
Nagata, 1993!, in others they involved communicative tasks ~e+g+, Leeman, 2003;
Muranoi, 2000; Rosa & Leow!, and in others they involved a mixture of the
two ~DeKeyser!+ Fourth, the treatment also differed in terms of whether it
Implicit and Explicit Corrective Feedback 343
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Table 1. Studies comparing the effects of different types of corrective feedback
Study Participants Target structure Design Tests Results
Carroll & Swain ~1993! 100 Spanish adult ESL learn-
ers ~low intermediate!
Dative verbs Groups: ~A! direct metalin-
guistic feedback, ~B! explicit
rejection, ~C! recast,
~D! indirect metalinguistic
feedback, ~E! control+
Treatment: two feedback
sessions, each followed by
recall ~i+e+, production with-
out feedback!+
Recall production tasks
following each feedback
session+
All of the treatment groups
performed better than the
control group on both recall
tasks+ Group A outper-
formed the other groups+
Nagata ~1993! 32 second-year university
learners of L2 Japanese
Japanese passive struc-
tures; verbal predicates and
particles
Groups: ~A! received feed-
back indicating what was
missing or not expected, ~B!
received same feedback
metalinguistic explanations+
Treatment: Learners per-
formed computer-based
exercises requiring them to
respond to sentences pro-
duced by an imaginary part-
ner+ Sentences were
computer-parsed and feed-
back on errors provided on
the basis of group
membership+
Written test using same
format as treatment task+
Group B significantly out-
performed group A on parti-
cles but not verbal
predicates+ Learners
expressed preference for
metalinguistic explanation+
DeKeyser ~1993! 25 Dutch high school
seniors learning L2 French
Variety of features, predomi-
nantly morphosyntactic
Groups: ~A! extensive
explicit corrective feedback
during normal class activi-
ties, ~B! limited explicit
corrective feedback+
Treatment: 10 class periods+
Three oral communication
tasks ~interview, picture
description, and
story-telling!+
Fill-in-the-blank test+
Tests administered twice+
No statistically significant
differences evident between
groups A and B+ Learners
with high previous achieve-
ment, high language apti-
tude, high extrinsic
motivation, and low anxiety
benefited the most from
error correction+
344
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Muranoi ~2000! 114 first-year Japanese col-
lege students
Indefinite article to denote
new information
Groups: ~A! interaction
enhancement ~IE! by means
of requests for repetition
and recasts in communica-
tive task formal debrief-
ing ~explicit grammar
explanation!, ~B! IE
meaning-focused debriefing,
~C! control ~no IE with
meaning-focused
debriefing!+
Grammaticality judgment
test+
Oral production task+
Written production task+
Two posttests 5 weeks
apart+
Both experimental groups
outperformed the control
group on both posttests+
Group A outperformed
group B on posttest 1 but
not on posttest 2+
Kim & Mathes ~2001! 20 Korean adult ESL learn-
ers ~high beginners and
intermediate!
Dative verbs Groups: ~A! received
explicit metalinguistic feed-
back, ~B! received recasts+
Treatment period: Feedback
was presented in two ses-
sions 1 week apart each
followed by production with
no feedback+
Controlled production tasks
~as in the treatment! with-
out feedback+
Differences between perfor-
mance on first and second
production tasks were not
significant+ Differences
between groups for gains in
production were not signifi-
cant+ Learners expressed
preference for explicit feed-
back+
Carroll ~2001! 100 adult low-intermediate
ESL learners
Forming nouns from verbs
~e+g+, “help” ~V! r “help0
helping” ~N! and distin-
guishing thing and event
nouns!
Groups: as in Carroll &
Swain ~1993!+
Elicited verb-noun conver-
sions in a sentence format+
All types of feedback helped
learners to learn the items
targeted by the feedback
but only explicit metalin-
guistic information ~group
A! and indirect prompting
~group D! enabled learners
to form a generalization+
Recasts did not facilitate
generalization+
Havranek & Cesnik ~2003! 207 university students
specializing in English
Variety of English phonolog-
ical, lexical, and grammati-
cal features
Data on 1700 corrective
feedback episodes from
normal English lessons+
Class-specific tests ~transla-
tion, correction, reading
aloud, and written and spo-
ken completion tasks!
directed at corrected items+
Effectiveness of corrective
feedback techniques was, in
order: ~1! elicited self-
correction, ~2! explicit rejec-
tion recast, ~3! recast
alone+
~continued !
Im
plicit
a
nd
ExplicitCorrective
Feedback
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Table 1 ~Continued!
Study Participants Target structure Design Tests Results
Leeman ~2003! 74 first-year university
learners of Spanish
Spanish noun-adjective
agreement
Groups: ~A! recast group,
~B! negative evidence group
~source or problem indi-
cated but not corrected!,
~C! enhanced salience with
no feedback, ~D! control
group+
Treatment: Participants
performed communicative
task one-on-one with
researcher+
Post- and delayed post-
picture description tasks+
Only groups A and C out-
performed the control
group on any posttest mea-
sure+ No difference between
A and C+
Sanz ~2003! 28 first-year university
learners of Spanish
Position of clitic pronouns
between object and verb
Groups: ~A! explicit metalin-
guistic feedback, ~B! implicit
feedback ~e+g+, “Sorry, try
again+”!+
Treatment: Computer-
delivered input processing
instruction without prior
explicit instruction+
Interpretation tests+
Production tests: ~a! sen-
tence completion and ~b!
written video retelling+
Both groups significantly
increased ability to inter-
pret and accurately produce
the target structure with no
difference between the
groups on any measure+
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Lyster ~2004! 148 ~grade 5! 10–11-year-
olds in a French immersion
program
French grammatical gender
~articles nouns!
Groups: ~A! received form-
focused instruction ~FFI!
recasts, ~B! FFI prompts
~including explicit feed-
back!, ~C! FFI only, ~D! con-
trol group+
Binary choice test+
Text completion test ~oral
production tasks!+
Object identification test+
Picture description test+
Two posttests: The second
administered 8 weeks after
the first+
Group B was only group to
outperform control group
on all 8 measures ~posttests
1 and 2!+ Group A outper-
formed control group on 5
of 8 measures+ Group C
outperformed control group
on 4 of 8 measures+ Statisti-
cally significant differences
were found between groups
B and C but not between A
and B+
Rosa & Leow ~2004!2 100 adult university learn-
ers of L2 Spanish enrolled
in advanced courses
Contrary to the fact condi-
tional sentences in the past
Groups: ~A! explicit feed-
back to both correct and
incorrect responses involv-
ing metalinguistic explana-
tion opportunity to try
again if incorrect, ~B!
implicit feedback indicating
whether the answer was
right or wrong, ~C! control
group+
Treatment: Computer-based
exposure to input-based
jigsaw task characterized by
task essentialness+
Three multiple-choice rec-
ognition tests and three
written controlled produc-
tion tests+
Immediate and delayed
posttests+
Results presented in terms
of old and new items+
Recognition tests: A statisti-
cally significant difference
evident between groups A
and B for new but not old
items+
Production tests: A statisti-
cally significant difference
was evident for the old but
not the new items+ Both
groups outperformed the
control group+
Im
plicit
a
nd
ExplicitCorrective
Feedback
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involved output processing ~the vast majority of the studies! or input process-
ing ~Rosa & Leow; Sanz, 2003!+ Fifth, the studies vary considerably in how they
operationalized implicit and explicit feedback+ Given the importance of this
variable, it is discussed in greater detail later in this section+ Sixth, variation
is evident in how learning was measured: Some studies utilized metalinguistic
judgments ~e+g+, Muranoi!, selected response, or constrained constructed
response formats ~e+g+, Havranek & Cesnik; Rosa & Leow!, all of which might
be considered to favor the application of explicit knowledge, whereas others
opted for a free constructed response format ~e+g+, Leeman!, which is more
likely to tap implicit knowledge+ Finally, the studies differ in another impor-
tant respect: Some included an explicit explanation of the grammatical target
prior to the practice activity ~e+g+, Lyster; Muranoi!, whereas others did not
~e+g+, Leeman; Sanz!+ These differences in design reflect the different purposes
of the studies, not all of which were expressly intended to compare implicit
and explicit corrective feedback+
Implicit feedback in these studies has typically taken the form of recasts
~Carroll, 2001; Carroll & Swain, 1993; Kim & Mathes, 2001; Leeman, 2003; Lys-
ter, 2004!+ However, Muranoi ~2000! employed both recasts and requests for
repetition+ Sanz ~2003! made use of only requests for repetition ~“Sorry, try
again+”!+ In Havranek and Cesnik’s ~2003! classroom study, which investi-
gated naturally occurring corrective feedback, a variety of more or less implicit
forms were identified, including recast, rejection recast, and recast rep-
etition+ This bears out the claims of Nicholas et al+ ~2001! and Ellis and Sheen
~in press! that recasts actually vary considerably in how implicit or explicit
they are+ It should be noted, therefore, that the recasts used in the different
studies might not have been equivalent in their degree of implicitness ver-
sus explicitness+
Explicit feedback has also been operationalized in very different ways+ A
minimal form of explicit feedback consists of simply indicating that an error
has been committed ~e+g+, Carroll & Swain’s, 1993, explicit rejection or Lee-
man’s, 2003, negative evidence!+ Rosa and Leow’s ~2004! implicit condition actu-
ally consisted of indicating whether the learners’ answers were right or wrong
and, thus, might have been more accurately labeled semiexplicit+ Carroll ~2001!,
Carroll and Swain, Nagata ~1993!, and DeKeyser ~1993! distinguished between
a form of minimal explicit feedback, involving some specification of the nature
of the error, and extensive corrective feedback, involving more detailed meta-
linguistic knowledge+ Lyster’s ~2004! prompts consisted of clarification requests,
repetitions ~with the error highlighted suprasegmentally!, metalinguistic clues,
and elicitation of the correct form+ Therefore, in Lyster’s sense, prompts include
both implicit and explicit forms of feedback+ The nonexperimental classroom
studies ~DeKeyser; Havranek & Cesnik, 2003! inevitably involved a variety of
explicit forms of correction+ All of these studies examined explicit correction
provided online immediately following learner utterances that contained errors+
In contrast, Muranoi’s ~2000! study investigated the effects of providing an
explicit grammar explanation after the treatment task had been completed+
348 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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Given the substantial differences in the purposes and designs of these stud-
ies, care needs to be taken in any attempt to generalize the findings+ However,
overall, the results point to an advantage for explicit over implicit corrective
feedback in studies in which the treatment involved production+ Carroll and
Swain ~1993! and Carroll ~2001! reported that the group that received direct
metalinguistic feedback outperformed all of the other groups in the produc-
tion of sentences involving dative verbs and noun formation and that this
type of feedback aids generalization to novel items+ Muranoi ~2000! found that
the group that received formal debriefing ~which included metalinguistic in-
formation! outperformed the group that received meaning-focused debrief-
ing, although only on the immediate posttest+ Havranek and Cesnik ~2003!
found that bare recasts were the least effective form of feedback in their class-
room study+ Lyster ~2004! reported that the group that received prompts
~which included metalinguistic feedback! performed better than the group that
received recasts on both immediate and delayed posttests+ There is also some
evidence that a comparison between two types of explicit feedback will show
that the more detailed metalinguistic feedback works better ~Nagata, 1993; Rosa
& Leow, 2004!+ It is also worth noting that the two studies that asked learners
about what type of feedback they preferred ~Kim & Mathes, 2001; Nagata!
reported a clear preference for more explicit feedback+
However, not all of the studies point to an advantage for explicit feedback+
DeKeyser ~1993! found no difference between the group that received exten-
sive explicit feedback and the group that received limited explicit feedback+
Nevertheless, his study indicated that when individual difference factors, such
as the learners’ proficiency and language aptitude, were taken into account,
the more explicit feedback was of greater benefit to the more able learners+
Kim and Mathes ~2001!, in a study that replicated that of Carroll and Swain
~1993!, also failed to find any statistically significant differences in the scores
of the explicit and implicit groups+ Explicit feedback that consists of simply
indicating that a problem exists does not appear to be helpful ~Leeman, 2003!+
In the one study that examined feedback as part of input-processing instruc-
tion ~Sanz, 2003!, explicit metalinguistic feedback did not confer any advan-
tage+ It is also important to recognize that these studies provide evidence that
implicit methods of feedback can assist learning+ The implicit groups in Car-
roll and Swain, Carroll ~2001!, Muranoi ~2000!, Leeman, and Lyster ~2004! all
scored higher than the control groups on the posttests+
The main limitation of the research to date lies in the method of testing+ As
noted previously, most of the studies did not include tests that can be consid-
ered valid measures of implicit knowledge ~i+e+, tests that call on learners to
access their linguistic knowledge rapidly online!+ The kinds of test used ~gram-
maticality judgment tests, sentence completion, picture prompt tests, transla-
tion tests! favored the use of explicit knowledge+ It can be argued, therefore,
that they were biased in favor of explicit corrective feedback+ The studies that
included a test likely to measure implicit knowledge did not provide clear com-
parisons of the effects of explicit and implicit feedback+ For example, Muranoi
Implicit and Explicit Corrective Feedback 349
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~2000! did not examine online feedback; in his study, feedback was provided
after the treatment tasks were completed+ Leeman ~2003!, as already pointed
out, did not examine explicit feedback that contained metalinguistic explana-
tions+ Lyster ~2004! did not examine metalinguistic clues separately from other
types of nonexplicit feedback designed to elicit the negotiation of form+
The study reported in this article investigated the following research
question:
Do learners learn more from one type of corrective feedback than from
another type?
This study was designed to provide a precise comparison between implicit
and explicit corrective feedback by operationalizing these constructs in
terms of ~a! partial recasts of those portions of learners’ utterances that
contained an error and ~b! metalinguistic explanations in which the learner’s
error was repeated and followed by metalinguistic information about
the target language rule but the correct target language form was not pro-
vided+ The effects of the corrective feedback on learning were assessed
by means of tests designed to measure learning of both implicit and explicit
L2 knowledge+
METHOD
The present study compares the effectiveness of two types of corrective feed-
back: explicit error correction in the form of metalinguistic information and
implicit error correction in the form of recasts+ Group 1 received implicit feed-
back ~recast group!, group 2 received explicit feedback ~metalinguistic group!,
and group 3 ~a testing control! had no opportunity to practice the target struc-
ture and, thus, received no feedback+ The relative effectiveness of both types
of feedback was assessed on an oral elicited imitation test, a grammaticality
judgment test, and a test of metalinguistic knowledge+ There were three test-
ing times: a pretest, an immediate posttest, and a delayed posttest+ The target
grammatical structure was past tense –ed+
Participants
The study was conducted in a private language school in New Zealand+ Three
classes of students ~n 34! were involved+ The school classified these classes
as lower intermediate, according to scores on a placement or a previous class
achievement test+ Information obtained from a background questionnaire
showed that the majority of learners ~77%! were of East Asian origin+ Most of
them had spent less than a year in New Zealand ~the mean length of stay was
just over 6 months!+ The mean age of all participants was 25 years+ The learn-
ers indicated that they had been formally engaged in studying English for any-
350 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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where from 8 months to 13 years, with an average length of time of 7 years+
Around 44% of participants indicated that their studies had been mainly for-
mal ~grammar-oriented! in nature, whereas 30% had received mainly informal
instruction, and the rest had received a mixture of both formal and informal
instruction+
The teaching approach adopted by the school placed emphasis on devel-
oping communicative skills in English+ Learners received between 3 and 5 hr
of English language instruction a day, for which they were enrolled as part-
time or full-time students+ Classes were arbitrarily assigned to one of the two
treatment options ~group 1 12 students, group 2 12 students! or to the
control group option ~group 3 10 students!+
Target Structure
Regular past tense –ed was chosen as the target structure for two reasons+
First, learners at the lower intermediate level are likely to already be familiar
with and have explicit knowledge of this structure+ Our purpose was not to
examine whether corrective feedback assists the learning of a completely new
structure, but whether it enables learners to gain greater control over a struc-
ture they have already partially mastered+ Pretesting demonstrated that this
was indeed the case: On the grammaticality judgment test, the learners scored
a mean of 75% on past tense –ed+ The second reason was that past tense –ed
is known to be problematic for learners and to cause errors ~e+g+, Doughty &
Varela, 1998!; thus, it was hypothesized that although learners at this level
would have explicit knowledge of this structure, they would make errors in
its use, especially in a communicative context and especially in oral produc-
tion ~oral production poses a problem because of Asian learners’ phonologi-
cal difficulties in producing consonant clusters with final @t# or @d#!+ Once again,
pretesting demonstrated that this was indeed the case: On the oral elicited
imitation test, which served as a measure of unplanned language use, the learn-
ers scored a mean of 30% on regular past tense –ed+
Regular past tense –ed is typically introduced in elementary and lower inter-
mediate textbooks, but it is not among the morphemes acquired early ~Dulay
& Burt, 1974; Makino, 1980!+ It is acquired after such morphemes as articles,
progressive –ing, and plural –s but before such morphemes as long plural ~–es!
and third person –s+ The typical error made by learners is the use of the sim-
ple or present form of the verb in place of V-ed: *Yesterday I visit my sister+
Hawkins ~2001! noted that some L2 learners “have difficulty in establishing
the regular pattern ~for past tense! at all” ~p+ 65!+
Instructional Materials
For the purposes of the study, each experimental group received the same
amount of instruction ~i+e+, a total of 1 hr over 2 consecutive days during which
Implicit and Explicit Corrective Feedback 351
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they completed two different half-hour communicative tasks!+ The control
group continued with their normal instruction+ They did not complete the tasks
and did not receive any feedback on past tense –ed errors+
The tasks were operationalized according to R+ Ellis’ ~2003! definition of
tasks; that is, they included a gap, they required learners to focus primarily
on meaning and to make use of their own linguistic resources, and they had a
clearly defined outcome+ They constituted what Ellis called focused tasks; in
other words, they were designed to encourage the use of particular linguistic
forms and, to this end, learners were provided with certain linguistic prompts
~see the description of each task!+
Task 1 (Day 1). Learners were assigned to four triads+ Each triad was
given the same picture sequence, which narrated a short story+ They
were also given one of four versions of a written account of the same story+
Each version differed in minor ways from the others+ Learners were told
that they would have only a couple of minutes to read the written account
of the story and that they needed to read it carefully because they would be
asked to retell it in as much detail as possible+ They were not allowed to
make any written notes+ The stories were removed and replaced with the list
of verbs in ~2! that learners were told they would need in order to retell the
story+
~2! visit live walk turn kill want follow attack laugh point stay watch
Learners were given about 5 min to plan the retelling of their story+ They were
told that they would not be able to use any prompts other than the picture
sequence and verb list+ The opening words of the story were written on the
board, to clearly establish a context for past tense: “Yesterday, Joe and Bill+
+ + +” Learners were then asked to listen to each triad’s collective retelling of
the story+ They were also told that each triad had been given a slightly differ-
ent version of the same story and that they were to listen carefully to identify
what was different+
Task 2 (Day 2). Learners were once again assigned to triads+ Each triad
was given a picture sequence depicting a day in the life of one of two char-
acters ~Gavin or Peter!+ Each picture sequence was different+ Pictures were
chosen to depict actions that would require the use of verbs with regular
past tense –ed forms+ Learners were given 5 min to prepare for recounting
the day of either Gavin or Peter+ Again, they were not allowed to take any
written notes+
Each triad was told to begin their account with “Yesterday Peter0Gavin had
a day off+” Learners in the other triads who were listening to the narrated
story were provided with an empty grid and pictures that they were to place
on the grid in the appropriate sequence, according to the narration+ One pic-
ture card did not fit, and learners were told they would be asked to identify
which card remained+
352 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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Instructional Procedures
The same instructor—one of the researchers—was responsible for conduct-
ing both tasks+ The learners had not met the instructor prior to the first
treatment session+ An observer sat in the classroom during each session to
manually record on paper all instances of the use of the target structure and
each instance of corrective feedback+ The treatment sessions were also
audio-recorded+
The learners received corrective feedback while they performed the tasks+
Group 1 received implicit feedback in the form of recasts, as in ~3!+
~3! Learner: + + + they saw and they follow follow follow him
Researcher: Followed
Learner: Followed him and attacked him+
The recasts were typically declarative and of the partial type and, as such,
might be considered to lie at the explicit end of the implicit-explicit contin-
uum for recasts ~see Sheen, in press!+ Nevertheless, because they intruded
minimally into the flow of the discourse, they might not have been very salient
to the learners+
The learners in group 2 received explicit feedback in the form of metalin-
guistic information, as in ~4!+
~4! Learner: He kiss her
Researcher: Kiss—you need past tense+
Learner: He kissed
In this example, which was typical of the corrective feedback episodes in this
study, the instructor first repeated the error and then supplied the metalin-
guistic information+ It is important to note that although corrective feedback
was directed at individual learners, the task was designed to ensure that the
attention of the whole class was focused as much as possible on the speaker
at these times+
Table 2 indicates the number of target forms that were elicited during each
task and the total number of incorrectly produced forms+ The number of
instances of feedback is also given+
Testing Instruments and Procedures
Five days prior to the start of the instructional treatments, the learners
involved in the study signed the consent forms, as required by the Univer-
sity of Auckland Human Participants Ethics Committee, and completed all of
the pretests+ The immediate posttesting was completed the day after the sec-
ond ~and last! day of instruction, and the delayed posttesting was completed
12 days later+ During each testing session, three tests were administered in
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the following order: untimed grammaticality judgment test, metalinguistic
knowledge test, oral imitation test+ The oral imitation test ~Erlam, in press!
was intended to provide a measure of the learners’ implicit knowledge,
whereas the untimed grammaticality judgment test ~especially the ungram-
matical sentences in this test; see R+ Ellis, 2005! and the metalinguistic test
were designed to provide measures of learners’ explicit knowledge+
R+ Ellis ~2004, 2005! discussed the theoretical grounds for these claims+ He
argued that tests of implicit knowledge need to elicit use of language where
the learners operate by feel, are pressured to perform in real time, are focused
on meaning, and have little need to draw on metalinguistic knowledge+ In con-
trast, tests of explicit knowledge need to elicit a test performance in which
the learners are encouraged to apply rules, are under no time pressure, are
consciously focused on form, and have a need to apply metalinguistic knowl-
edge+ The oral imitation test was designed to satisfy the criteria for tests of
implicit knowledge, whereas the untimed grammaticality judgment test and
the metalinguistic test were designed to meet the criteria for tests of explicit
knowledge+ The tests are described in detail in the following subsections+
Oral Imitation Test. This test consisted of a set of 36 belief statements+
Statements were grammatically correct ~n 18! or incorrect ~n 18!+ They
consisted of 12 statements that targeted simple past tense –ed, 12 that tar-
geted comparative adjectives ~a focus of another study!, and 12 distracter
items+ Examples of the past tense –ed items are given in ~5!+
~5! a+ Everyone liked the movie Star Wars+
b+ *An American invent Microsoft Word+
Statements included target items introduced during the instructional treat-
ments ~old items! and new items+ The statements containing new items were
designed to test whether learners were able to generalize what they had
learned to new vocabulary items+ Eight of the 12 statements targeting past
tense –ed presented the target structure in the context of new items+
Table 2. Number of target forms elicited and instances of feedback
Type of feedback
Total target
forms eliciteda
Total incorrect
target forms elicited
Instances
of feedback
Recast
Lesson 1 44 32 24
Lesson 2 48 30 28
Metalinguistic
Lesson 1 52 21 17
Lesson 2 50 24 23
aCorrect and incorrect+
354 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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Each statement was presented orally, one at a time, on an audiotape: Test-
takers were required to first indicate on an answer sheet whether they agreed
with, disagreed with, or were not sure about the statement+ They were then
asked to repeat the statement orally in correct English+ Pretest training pre-
sented learners with both grammatical and ungrammatical statements ~not
involving past tense –ed ! to practice with, and they were given the correct
responses to these items+ Learners’ responses to all items were audio-recorded+
These were then analyzed to establish whether obligatory occasions for use
of the target structure had been established+ Errors in structures other than
the target structure were not considered+ Each imitated statement was allo-
cated a score of either 1 ~the grammatically correct target structure was cor-
rectly imitated or the grammatically incorrect target structure was corrected!
or 0 ~the target structure was avoided, the grammatically correct target struc-
ture was attempted but incorrectly imitated, or the grammatically incorrect
target structure was imitated but not corrected!+ If a learner self-corrected,
then only the initial incorrect production was scored, as it was felt that this
would provide the better measure of learners’ implicit knowledge+ Scores were
expressed as percentage correct+ Three versions of the test were created for
use over the three testing sessions; in each, the same statements were used
but presented in a different order+ Reliability ~Cronbach’s alpha! for the pre-
test was +779+ For more information about the theoretical rationale for this
test and its design, see Erlam ~in press!+
Grammaticality Judgment Test. This was a pen-and-paper test consisting
of 45 sentences+ Fifteen sentences targeted past tense –ed, and the remainder
targeted 30 other structures+ Of the 15 sentences, 7 were grammatically cor-
rect and 8 were grammatically incorrect+ Sentences were randomly scrambled
in different ways to create three versions of the test+ Test-takers were required
to ~a! indicate whether each sentence was grammatically correct or incorrect,
~b! indicate the degree of certainty of their judgment ~as proposed by Sorace,
1996! by typing a score on a scale marked from 0% to 100% in the box pro-
vided, and ~c! self-report whether they used a rule or feel for each sentence+
Learners were given six sentences to practice on before beginning the test+
Each item was presented on a new page, and test-takers were told that they
were not allowed to turn back to look at any part of the test that they had
already completed+ For past tense –ed, 7 of the 15 statements presented the
target structure in the context of new vocabulary and 8 presented the target
structure in the context of vocabulary included in the instruction+ Learners’
responses were scored as either correct ~1 point! or incorrect ~0 points!+ In
addition to the total score, separate scores for grammatical and ungrammati-
cal test items and also for new and old verb items were calculated+ Reliability
~Cronbach’s alpha! for the pretest was +63+ Test-retest reliability ~Pearson’s r!
was calculated for the control group ~n 10! only+ For the pretest and imme-
diate posttest, it was +65 ~p , +05!, and for the pretest and delayed posttest, it
was +74 ~p , +05!+
Implicit and Explicit Corrective Feedback 355
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Metalinguistic Knowledge Test. Learners were presented with five sen-
tences and were told that they were ungrammatical+ Two of the sentences con-
tained errors in past tense –ed+ The part of the sentence containing the error
in each example was underlined+ Learners were asked to ~a! correct the error
and ~b! explain what was wrong with the sentence ~in English, using their own
words!+ They were shown two practice examples+ As in the previous test, each
item was presented on a new page and test-takers were told that they were
not allowed to turn back+ Learners were scored one point for correcting the
error and one point for a correct explanation of the error+ A percentage accu-
racy score was calculated+
Analysis
Descriptive statistics for the three groups on all three tests were calculated+
On the oral imitation test and the grammaticality judgment test, ~a! total scores,
~b! separate scores for grammatical and ungrammatical items, and ~c! sepa-
rate scores for old and new items were calculated+ The decision to examine
grammatical and ungrammatical items separately was motivated by previous
research ~see R+ Ellis, 2005!, which showed that these might measure different
types of knowledge ~i+e+, ungrammatical sentences provide a stronger mea-
sure of explicit knowledge!+ The decision to examine old items ~i+e+, items that
tested verbs included in the instructional treatment! versus new items ~i+e+,
verbs not included in the instructional treatment! was motivated by the wish
to examine whether the instruction resulted only in item learning or whether
there was also evidence of system learning+
The t-tests showed that there were statistically significant differences among
the groups on the oral imitation and grammaticality judgment pretests+ To
take account of this difference, analyses of covariance ~ANCOVAs; with pre-
test scores as the covariate! were computed to investigate to what extent group
differences on the two posttests were statistically significant+
RESULTS
Oral Imitation Test
The descriptive statistics for regular past tense on the imitation test ~see
Table 3! show a range in overall accuracy from 24% to 39% on the pretest+
The scores increase on both posttests+ The ungrammatical items have lower
accuracy scores than the grammatical items+
The results of the ANCOVAs reveal that there is a significant difference
between the groups on their pretest scores+ Once these differences are taken
into account, there is no effect for group on the immediate posttest, F~2, 34!
0+961, p +394; however, there is on the delayed posttest, F~2, 34! 7+975, p ,
+01+ The post hoc contrasts for the delayed posttest show that the metalin-
356 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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guistic group differed significantly from the recast and control groups+ There
was also a tendency toward a significant difference between the recast and
control groups+
The analysis of the grammatical and ungrammatical items showed no sig-
nificant group differences on the immediate posttest for either the grammati-
cal, F~2, 34! 0+853, p +436, or ungrammatical items, F~2, 34! 0+753, p
+480+ However, on the delayed posttest, there were significant differences on
both the grammatical, F~2, 34! 6+697, p , +01, and ungrammatical items, F~2,
34! 4+769, p , +05, with the metalinguistic group differing significantly from
the control on both+ Additionally, the metalinguistic group differed signifi-
cantly from the recast group on the grammatical items, with a similar trend
toward significance for metalinguistic over recasts on the ungrammatical items+
Untimed Grammaticality Judgment Test
The descriptive statistics for regular past tense on the grammaticality judg-
ment test ~see Table 4! show relatively high levels of accuracy on the pretest,
ranging from 69% to 78%+ These accuracy scores generally increased over both
posttests+
The ANCOVAs show overall that there is no difference for group on the
immediate posttest, F~2, 34! 0+714, p +498, although there is for the delayed
posttest, F~2, 34! 4+493, p , +05+ The post hoc contrasts for the delayed
posttest showed that the metalinguistic group differed significantly from the
recast group and that there was a trend toward significance for metalinguistic
over the control+
Table 3. Imitation test results
Pretest
Immediate
posttest
Delayed
posttest
Groups M SD M SD M SD
Recast
Grammatical 0+278 0+278 0+403 0+279 0+514 0+180
Ungrammatical 0+194 0+282 0+319 0+240 0+375 0+334
Total 0+236 0+164 0+361 0+228 0+444 0+223
Metalinguistic
Grammatical 0+444 0+192 0+618 0+257 0+736 0+194
Ungrammatical 0+333 0+225 0+375 0+267 0+653 0+694
Total 0+389 0+164 0+497 0+211 0+694 0+196
Control
Grammatical 0+307 0+207 0+417 0+317 0+400 0+211
Ungrammatical 0+200 0+172 0+217 0+209 0+267 0+196
Total 0+253 0+147 0+317 0+188 0+333 0+152
Implicit and Explicit Corrective Feedback 357
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The ANCOVAs do not reveal any group differences on the immediate post-
test for the grammatical F~2, 34! 1+482, p +243, or ungrammatical items
F~2, 34! 0+092, p +912+ Additionally, there were no differences on the delayed
posttest for the ungrammatical items, F~2, 34! 0+900, p +417+ However, there
were significant differences on the delayed posttest for the grammatical items,
F~2, 34! 5+194, p , +05, with the post hoc contrasts showing that the meta-
linguistic group differed significantly from the recast group, and the control
differed significantly from the recasts+
The Metalinguistic Test
The results from the metalinguistic test ~see Table 5! show that all three groups
had high accuracy scores on the pretest and that these generally remained
Table 4. Grammaticality judgment test results
Pretest
Immediate
posttest
Delayed
posttest
Groups M SD M SD M SD
Recast
Grammatical 0+714 0+122 0+833 0+147 0+784 0+142
Ungrammatical 0+854 0+129 0+844 0+152 0+813 0+146
Total 0+784 0+062 0+839 0+071 0+798 0+075
Metalinguistic
Grammatical 0+738 0+134 0+929 0+114 0+941 0+074
Ungrammatical 0+844 0+108 0+833 0+154 0+844 0+094
Total 0+791 0+073 0+881 0+115 0+892 0+065
Control
Grammatical 0+586 0+247 0+786 0+181 0+871 0+142
Ungrammatical 0+788 0+145 0+813 0+189 0+738 0+190
Total 0+687 0+135 0+799 0+098 0+805 0+096
Table 5. Metalinguistic test results
Pretest
Immediate
posttest
Delayed
posttest
Groups M SD M SD M SD
Recast 0+958 0+144 0+833 0+326 1+00 0+000
Metalinguistic 0+833 0+246 0+917 0+194 0+917 0+194
Control 0+850 0+241 0+900 0+210 0+850 0+337
358 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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high over the two posttests+ Due to the small number of test items ~n 2!,
inferential statistics were not calculated for the metalinguistic test+
Old versus New Items
Tables 6 and 7 present the descriptive statistics for test performance on past
tense verbs that appeared in the treatment tasks ~i+e+, old items! and for past
tense verbs that were not the object of feedback ~i+e+, new items!+ If the effect
of the treatment were only evident on the old items, this would suggest that
corrective feedback caters only to item learning; if the effect could be shown
Table 6. Imitation: new0old item results
Pretest
Immediate
posttest
Delayed
posttest
Groups M SD M SD M SD
Recast
New 0+226 0+247 0+286 0+220 0+345 0+232
Old 0+250 0+309 0+467 0+287 0+583 0+301
Metalinguistic
New 0+321 0+203 0+373 0+230 0+631 0+223
Old 0+483 0+232 0+657 0+265 0+783 0+233
Control
New 0+271 0+171 0+271 0+228 0+271 0+196
Old 0+210 0+242 0+380 0+239 0+420 0+148
Table 7. Grammaticality judgment test: new0old item results
Pretest
Immediate
posttest
Delayed
posttest
Groups M SD M SD M SD
Recast
New 0+823 0+113 0+854 0+139 0+802 0+125
Old 0+750 0+184 0+821 0+138 0+792 0+116
Metalinguistic
New 0+740 0+135 0+875 0+131 0+906 0+094
Old 0+857 0+122 0+881 0+147 0+869 0+129
Control
New 0+613 0+092 0+800 0+121 0+750 0+156
Old 0+786 0+226 0+800 0+154 0+857 0+117
Implicit and Explicit Corrective Feedback 359
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to extend to new items, this would constitute evidence of generalization ~i+e+,
system learning!+
The results of the ANCOVAs reveal that there were significant differences
between the groups on the pretest oral imitation scores+ Once these differ-
ences are taken into account, there were no differences for the new items on
the immediate posttest, F~2, 34! 0+397, p +676; however, there were differ-
ences on the delayed posttest, F~2, 34! 8+943, p , +01+ The post hoc con-
trasts show that the metalinguistic group is significantly more accurate than
both the recast and control groups+ Similarly, for the old items, there was no
difference on the immediate posttest, F~2, 34! 1+211, p +312, but there was
on the delayed posttest, F~2, 34! 3+188, p +056, with the post hoc contrasts
showing that the metalinguistic group was significantly more accurate than
the control group+ Thus, the results reported for the oral imitation test as a
whole apply equally to old and new items+
The results of the ANCOVAs for the grammaticality judgment test reveal
that there were significant differences between the groups on the pretest
scores+ Once these differences are taken into account, there was no differ-
ence among the groups for the old items on either the immediate posttest,
F~2, 34! 0+452, p +640, or the delayed posttest, F~2, 34! 0+817, p +451,
nor for the new items on the immediate posttest, F~2, 34! 0+467, p +632+
However, there was a significant difference for the new items on the delayed
posttest, F~2, 34! 4+295, p , +05, which showed the metalinguistic group to
be significantly more accurate than the recast group as well as a trend toward
metalinguistic group over the control group+
Summary
Table 8 summarizes the main results, focusing on the statistically significant
differences in the pairwise comparisons+
DISCUSSION
An inspection of the pretest oral imitation test scores suggests that all of the
learners initially had only limited implicit knowledge of past tense –ed+ This
was especially apparent in their inability to produce the correct forms when
asked to imitate and correct sentences containing errors in structure+ In con-
trast, the grammaticality judgment pretest scores were high ~i+e+, above 70%
in the two experimental groups!+ It is also noticeable that scores on the ungram-
matical sentences were higher than on the grammatical sentences+ If the
ungrammatical sentences are taken as affording a better measure of explicit
knowledge than the grammatical sentences, as suggested by R+ Ellis ~2004!
and demonstrated in R+ Ellis ~2005!, this might explain the higher scores on
the ungrammatical sentences+ Also, the metalinguistic test indicated a high
360 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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Table 8. Summary of statistically significant differences
Test Pretest Immediate posttest Delayed posttest
Oral imitation
Overall Significant group differences No significant differences M . C ~old and new items!
M . R ~new items!
R . C ~trend!
Grammatical Significant group differences No significant differences M . C, R
Ungrammatical Significant group differences No significant differences M . C
M . R ~trend!
Grammaticality judgment
Overall Significant group differences No significant differences M . C ~trend!
M . R ~new items!
Grammatical Significant group differences No significant differences M, C . R
Ungrammatical Significant group differences No significant differences No significant differences
Note+ M metalinguistic group; R recast group; C control group+
Im
plicit
a
nd
ExplicitCorrective
Feedback
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level of explicit knowledge of past tense –ed+ Thus, the pretest scores can be
interpreted as showing that the learners generally possessed a high level of
explicit knowledge of past tense –ed but were lacking in implicit knowledge+
The descriptive statistics in Table 3 and the results of the ANCOVAs show
that the corrective feedback resulted in significant differences among the
groups on the oral imitation test for past tense –ed, but these differences were
only evident on the delayed posttest+ Corrective feedback also led to gains on
the grammaticality judgment test+ However, the gains were almost entirely due
to improved performance on the grammatical sentences, which R+ Ellis ~2004,
2005! argued tap more into implicit knowledge+
These results suggest that corrective feedback has an effect on the learn-
ing of implicit knowledge+ Indeed, overall, the feedback appears to have had a
greater effect on the learners’ implicit knowledge than on their explicit knowl-
edge, although this might simply reflect the fact that the learners possessed
ceiling levels of explicit knowledge at the beginning of the study+ It is possi-
ble, of course, that the treatments increased learners’ awareness of the gram-
matical targets of the oral imitation test, thus encouraging them to monitor
their output using their explicit knowledge+ However, we do not believe that
this occurred+ First, when asked at the end of the final test if they were aware
of which grammatical structures the test was measuring, only one learner was
able to identify past tense+ Second, as Table 9 shows, there is no clear evi-
dence that the experimental groups were monitoring more than the control
group or more in the posttests than in the pretest+ If the learners were attempt-
ing to use their explicit knowledge in this test, we would have expected a
much higher incidence of self-correction+3
Further evidence that the corrective feedback induced changes in learn-
ers’ implicit knowledge can be found in the fact that the effects of the exper-
imental treatments on the oral imitation test scores were more evident 2 weeks
after the instruction than 1 day after+ This finding reflects previous research
~e+g+, Mackey, 1999!, which has also shown that the effects of instruction
become more apparent in delayed tests that tap the kind of language use likely
to measure implicit knowledge+ The enhanced accuracy evident in the oral
imitation delayed posttest is indicative of the learners’ successful incorpora-
tion of the target structure into their interlanguage systems+
Table 9. Number of instances of participant
self-correction during the oral imitation test
Group Pretest
Immediate
posttest
Delayed
posttest
Metalinguistic 3 1 4
Recasts 1 7 2
Control 2 1 3
362 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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The main purpose of the study was to investigate the relative effects of
explicit and implicit corrective feedback on the acquisition of both types of
knowledge+ In this study, explicit corrective feedback was operationalized as
metalinguistic information, and implicit corrective feedback was operational-
ized as recasts+ The results point to a distinct advantage for metalinguistic
information despite the fact that the learners in the recast group received sub-
stantially more corrective feedback than those in the metalinguistic group ~see
Table 2!+ Nor was the advantage found for the metalinguistic group only evi-
dent in the grammaticality judgment test: It was also clearly evident in the
oral imitation test+ Also, metalinguistic feedback ~but not recasts! was found
to result in learning that generalized to verbs not included in the treatment,
which suggests that system learning took place+
How can we explain the general superiority of explicit feedback over implicit
feedback? In the earlier discussion of theoretical issues relating to corrective
feedback, we noted that in connectionist models of L2 acquisition, explicit
corrective feedback in the context of communicative activity can facilitate the
conversion of explicit knowledge into implicit knowledge+4 Explicit feedback
is more likely than implicit feedback to be perceived as overtly corrective, as
the examples in ~6! and ~7! suggest+ In both episodes, the teacher’s feedback
move overlaps with the learner’s preceding move, but because the metalin-
guistic feedback is longer ~six words as opposed to one!, it might have been
better attended to and perceived as overtly corrective+ In both episodes, how-
ever, the learner successfully repairs the error following the feedback move,
but, again, there is evidence of greater awareness that repair is needed in the
metalinguistic episode+Whereas in ~6! the learner simply repeats the reformu-
lated past tense verb, in ~7! the learner’s “yes” seems to overtly acknowledge
that repair was required+ Thus, metalinguistic feedback—in comparison to
recasts—seems more likely to lead to greater depth of awareness of the gap
between what was said and the target norm, thereby facilitating the acqui-
sition of implicit knowledge+ It is also important to recognize that the meta-
linguistic feedback, as illustrated in ~7!, does not intrude unduly in the
communicative flow of the activity+ It constitutes a brief time-out from com-
municating, which allows the learner to focus explicitly but briefly on form+
The effectiveness of the metalinguistic feedback, therefore, might derive in
part from the high level of awareness it generates and in part from the fact
that it is embedded in a communicative context+
~6! L: yesterday two boys, Joe and Bill visit their rich uncle
T: Visited
L: Visited their rich uncle+
~7! L: yesterday Joe and Bill ah went to ah Bill’s grandmother and visit their grand-
mother
T: and visit . you need past tense
L: Visited, yes+
Key: signifies overlapping elements; . signifies rising intonation; L Learner;
T Teacher
Implicit and Explicit Corrective Feedback 363
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The superiority of the metalinguistic feedback only reached statistical sig-
nificance in the delayed oral imitation and grammaticality judgment post-
tests+ However, gains from pretest to the immediate posttest were also evident+
Thus, the general pattern of the results was: pretest scores , immediate post-
test scores , delayed posttest scores; that is, the benefits of the metalinguis-
tic feedback became more evident as time passed+ This finding supports the
claims of R+ Ellis ~1994! and N+ C+ Ellis ~2005! that explicit L2 knowledge can
enhance the processes involved in the development of implicit knowledge ~e+g+,
noticing and cognitive comparison!; that is, the awareness generated by meta-
linguistic feedback promotes the kind of synergy between explicit and implicit
knowledge that is hypothesized to underlie L2 learning+
The relatively weak effect found for either type of feedback on the ungram-
matical sentences in the grammaticality judgment test reflects the fact that
the learners possessed the explicit knowledge required for judging such sen-
tences from the beginning, which was clearly evident from their high pretest
scores on the ungrammatical sentences on the grammaticality judgment test
and near-perfect scores on the metalinguistic test+
One final comment is in order+ All of the learners in this study demon-
strated partial implicit knowledge of past-tense –ed, as demonstrated by their
performance on the oral imitation pretest+ It is possible that for corrective
feedback of any kind to have an effect on learning, the structures must be at
least partially established in the learners’ interlanguages+ Further research is
needed to establish whether corrective feedback is effective in enabling learn-
ers to acquire completely new grammatical structures+
CONCLUSION
This study demonstrates that explicit feedback in the form of metalinguistic
information is, overall, more effective than implicit feedback ~in the form of
recasts! and contributes to system as well as item learning+ Table 10 summa-
rizes the actions that learners are hypothesized to carry out in order to pro-
cess feedback for acquisition ~based on Carroll’s, 2001, account of corrective
feedback!, and the extent to which the two types of feedback engage these
processes+ It illustrates how both implicit and explicit types of feedback might
facilitate these actions and it demonstrates why explicit feedback might do
so more effectively than implicit feedback+ In particular, explicit feedback seems
more likely to promote the cognitive comparison that aids learning+
The study reported in this paper incorporated a number of unique meth-
odological features+ To the best of our knowledge, this is the first experimen-
tal study that has compared the effects of online explicit corrective feedback
in the form of metalinguistic explanations and implicit corrective feedback in
the form of recasts in classroom-based instruction+ Other studies that have
compared explicit and implicit corrective feedback ~see Table 1! have either
examined other forms of corrective feedback or have been laboratory based,
364 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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or both+ We argue that metalinguistic explanation and recasts constitute the
best exemplars of explicit and implicit corrective feedback, as both are sup-
ported by previous research that shows them to be effective in promoting
learning+ We also argue that from a pedagogical perspective, it is important to
examine corrective feedback within the classroom context+ We do not believe
that it is easy to extrapolate the results obtained from laboratory studies that
involve one-on-one interactions to classrooms in which the teacher interacts
with the whole class+ In our view, ecological validity can only be achieved
through classroom-based research+
Table 10. Facilitative potential of implicit and explicit feedback compared
General action Specific step
Implicit feedback
~recasts!
Explicit feedback
~metalinguistic
information!
Detecting the error The learner’s atten-
tion must switch
from meaning to
form; this can only
occur if the correc-
tive intention is rec-
ognized, which
happens only if the
feedback is perceived
as irrelevant to the
ongoing discourse+
Partial recasts are
more likely to induce
a switch in attention
from meaning to form
than full recasts;
however, the correc-
tive force of partial
recasts is not self-
evident, as repeti-
tions serve other
functions in dis-
course+
Metalinguistic infor-
mation is clearly
irrelevant to the
ongoing discourse,
which makes a switch
from meaning to form
likely and the correc-
tive intention of the
feedback clear+
The learner must be
able to locate the
error+
Recasts make the
location of the error
clear+
Repeating the error
and then giving a
metalinguistic clue
makes the location of
the error clear+
Correcting the error The learner must be
able to distinguish
the phonological
dissimilarity between
his or her erroneous
form and the target
form in the feedback+
Recasts make it pos-
sible for the learner
to compare two pho-
nological forms ~the
erroneous form and
the target form!, but
the learner has to
attend to the
difference+
The process of com-
paring the erroneous
and target phonologi-
cal form is enhanced
because the teacher
repeated the incor-
rect form before sup-
plying metalinguistic
information+
The learner must be
able to decide
whether pronuncia-
tion, morphology,
syntax, or semantics
is causing the prob-
lem+ The learner can
make use of explicit
knowledge to decide+
Recasts provide no
clues as to the nature
of the error; that is,
the learner is left to
infer whether the
error is one of pro-
nunciation or mor-
phology+
The nature of the
error is made clear+ A
connection is made
between the implicit
use of a specific form
~the error! and an
explicit representa-
tion of the target
form required+
Note+ Recasts refer to partial recasts of the kind used in this study+
Implicit and Explicit Corrective Feedback 365
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Another unique feature is that the corrective feedback occurred in the con-
text of learners performing communicative tasks+ In Long’s ~1991! terms, there-
fore, the feedback constituted focus-on-form+ In the majority of studies listed
in Table 1, the feedback was part of a focus-on-forms+ The importance of the
study reported in the preceding sections is that it demonstrates that when
learners receive explicit feedback on their attempts to communicate, acquisi-
tion takes place+ Thus, the study supports Long’s claims about focus-on-form+
In the view of the teacher who taught the lessons and of the researchers who
inspected the transcripts of the corrective feedback episodes, the learners
were engaged with performing the tasks and the primary focus was on mean-
ing, not form+ The study demonstrates that metalinguistic feedback does not
detract unduly from the communicative flow of a lesson+
A third unique feature of the study is to be found in the instruments used
to measure learning+ These measures were based on prior research designed
to develop relatively separate measures of implicit and explicit knowledge ~R+
Ellis, 2005; Erlam, in press!+ These measures enable us to consider whether
the effects of the corrective feedback were related to implicit as well as explicit
knowledge+ The results reported earlier suggest that corrective feedback results
in gains in implicit knowledge+ As such, they constitute evidence against the
claims that have been advanced by some theorists ~Krashen, 1982; Schwartz,
1993! that corrective feedback plays no part in the development of implicit
knowledge+
As in all classroom studies, there are inevitable limitations+ First, the sam-
ple size for this study was small+ Also, we were forced to use intact groups,
with the result that the groups were not equivalent at the commencement of
the study, thus obligating the use of ANCOVA+ Second, because our main aim
was to compare the relative effectiveness of the two types of corrective feed-
back, we only included a testing group as a control group ~i+e+, we did not
have a control group that completed the communicative tasks without any
corrective feedback!+ Third, the length of the treatments was very short
~approximately 1 hr!+ It is possible that with a longer treatment, recasts would
have proved more effective+ Fourth, the structure we chose for study was a
structure that the learners had already begun to acquire+ In one respect, this
can be considered a strength, as it enabled us to examine which type of cor-
rective feedback works best for structures already partially acquired+ How-
ever, in another respect, it constitutes a weakness, in that we are unable to
say whether corrective feedback ~and what type of corrective feedback! is
effective in establishing new knowledge+ As always, further research is needed+
NOTES
1+ Other studies have examined the relationship between implicit0explicit feedback and learner
uptake ~e+g+, Oliver & Mackey, 2003!, but these are not included in this review, which focuses exclu-
sively on the effects of feedback on L2 acquisition as measured in posttests+ The extent to which
uptake constitutes a measure of acquisition is controversial, with many researchers, including our-
selves, preferring to view it as evidence of noticing+
366 Rod Ellis, Shawn Loewen, and Rosemary Erlam
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2+ Rosa and Leow’s ~2004! study also involved other experimental conditions+ These depended
on whether there was a prior grammatical explanation of the target feature+ The feedback condi-
tions summarized in Table 1 did not include any prior explanation+
3+When scoring the oral imitation test, self-corrections were discounted+
4+ A reviewer of a draft version of this paper pointed out that the results could be explained in
terms of the learners’ having automatized their declarative knowledge of past tense –ed as a result
of the treatment+ This interpretation draws on the distinction between declarative and procedural
knowledge, which informs skill-building theories of the kind advocated by DeKeyser ~1998!+ How-
ever, we have chosen to frame the paper in terms of the implicit0explicit distinction, noting with
Eysenck ~2001! that recent changes in the definitions of both pairs of terms have brought them
closer together, making it “increasingly difficult to decide on the extent to which different theories
actually make significantly different predictions” ~p+ 213!+
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