In modern language learning research and theory a distinction is generally made between a language learner’s competence and a language learner’s performance. Competence in this case, refers to the learner’s knowledge or ability to use the target language. It is assumed that this knowledge or ability is in the mind of the learner. Because it is in the mind of the learner it is assumed that it stays relatively consistent from one moment to the next. Furthermore, because it is in the mind of the learner it cannot be directly observed by a researcher. One can never actually see the knowledge or ability in a learner’s mind. One must infer it by observing the learner’s behavior or performances on tests. Competence is distinguished from performance. Performance in this case refers to the actual use of that language knowledge or ability. Performance is not knowledge or ability, it is actions. Learners use their unseen ability to do visible or testable actions such as speaking, writing, listening, or reading. In this sense, performance is the product of competence. It is competence put to use or put into actions. Whereas competence is not testable, performance is.

Competence, according to Chomsky’s original notion, would be the learner’s ability to use the language under the most "ideal" circumstances. While a learner’s actual performance may vary from one moment to the next, it is believed that the competence does not. For example, if a language learner is speaking but gets confused due to some distraction her visible and testable performance may drop. Although her performance has dropped, it is assumed that her competence, her actual knowledge or ability to use the language, is still the same. This is made clearer by an extreme example. Imagine that someone kidnapped you, tied you up, and put tape over your mouth. In that situation you would not be able to speak. Your performance would be completely gone. Yet, in your head, you would still have your knowledge about English – you would still have your competence. Thus it is believed that competence stays consistent despite circumstances that affect performance.

Performance, unlike competence, varies according to circumstances. A learner’s performance can go down or even disappear when she is affected by variables such as stress, exhaustion, or distractions. When variables such as these cause the learner’s performance to appear lower than her actual competence, it is called a mistake. For example, even a native speaker will make mistakes despite having perfectly complete competence. Native speakers, despite their perfect competence, may forget to use the third person singular ‘s’ morpheme when making sentences that are unusually long or when a little confused by the complexity of the ideas they are trying to express. This does not mean that they lack competence, it merely means they made a mistake. Mistakes are normal and unavoidable in even the best of all speakers.

Not all problems in production are simple mistakes though, some are caused by a lack of competence. When problems in performance are caused by a lack of competence instead of just performance variables, we call them errors. For example, a person who has not successfully acquired the past tense form yet may make sentences such as "Yesterday I go to the store." Thus the absence of certain forms in the learner’s production can be a sign that they are absent in the competence as well. Likewise, rules in the competence may be overgeneralized. For example, a learner who is just beginning to acquire the past tense ‘ed’ morpheme may say, "Yesterday I goed to the store", overgeneralizing the ‘ed’ morpheme to places where it should not be. In other cases, two or more forms may be confused for one another if they have similar meaning, sound, or function. An example of this can be found in language learners who confuse the words ‘boring’ and ‘bored’. They might say, "The book was bored" or "I was boring". As evident from these examples, errors can generally be distinguished from mistakes by their systematic nature and relative consistency. Incomplete or incorrect competence will systematically and consistently cause incomplete or incorrect performance. When such errors are being made, it is safe to assume that the learner either does not clearly know the troublesome form or that the learner knows the form but has had enough practice to internalized it yet.

This last detail about errors leads to some debate. Often second language learners have studied a grammar form and know it explicitly but still cannot use it consistently during communication. Sometimes this condition may last for an extremely long time. Some of my own students for example have been studying English for over thirty years. They may have first learned about the third person singular ‘s’ morpheme (e.g. He likes spaghetti) thirty years ago but still cannot use it well despite decades of effort. Those learners know the form but still seem to be lacking some sort of competence. In other cases, some learners use a form very inconsistently. Sometimes they can use it correctly and sometimes not. They must also be lacking some sort of competence.

Because such cases clearly exist in second language learning one must either conclude that only implicit and automatized knowledge is true competence, or that there are different kinds of competence. If we only count implicit an automatized knowledge as true competence, then we would not include explicit knowledge. This means that, my students who have studied the third person singular form and know it well on tests but cannot use it consistently when speaking, would be said to not really have acquired it yet. In this sense, competence is knowledge, but not normal knowledge. If you choose to believe that there are different kinds of competence, then we could say that those students of mine have one kind of competence that comes from studying, but do not have the most important kind that comes from experience with communication. In this case both explicit and implicit knowledge would be considered competence but only one would be true communicative competence. Yet another more reasonable explanation would be to say that they are all competence but conclude that the knowledge in competence can exist in various stages of internalization. In this view, the goal of the learner is still to acquire implicit and automatized knowledge through experience with communication. Knowledge could start out in one form such as explicit knowledge obtained through studying. This competence would be very "shallow" though. The learner in this case would know the rule but forget it whenever confused. Over time and through meaningful practice however, the knowledge could work its way deeper into the learner’s competence. Thus there would be layers of competence, some shallow and some deep. The more deeply internalized knowledge would be more automatized and therefore more useful during real communication under pressure. The shallow knowledge that is not yet internalized could be useful when the learner has time to plan sentences or when the learner is editing something, but would not be useful during real communication.

In conclusion, the notion of distinguishing competence from performance in language learning theory is very necessary. It would not be fair to judge a learner based totally on her test performances. We must assume that there is always more inside that we cannot see. We must also realize that behind all performance is some source and that to understand language learning is to understand that source and how it works. Once we begin to distinguish competence from performance however, it begins to get much more complicated. How can we know for sure what competence is when performance is so variable? How can we ever judge whether a learner has truly finished acquiring a form?

activity

Read about the following language learners and decide whether they are making errors, mistakes, or neither.

Sally is learning English as a first language. She is only three and a half. She always says "Yesterday I goed to school."

Mr. Kim is a non-native speaker learning English. Although he knows the past tense forms very well he sometimes forgets to use them when he is speaking.

Ms. Choi is a non-native speaker learning English. When she is very nervous or feeling unconfident she gets her pronouns confused (he/she).

John Freen is a native speaker, but when he speaks he always uses Black American English. For example, he might say "I be studying all night" to mean "I study all night every night".

Ms. Park is a non-native speaker learning English. She does not know much about grammar. She usually uses articles (the/a/an) correctly when speaking but cannot explain any of the rules to you if you ask.

Susan Smith is an American native speaker but always says "There’s two cats" instead of "There are two cats".

Mindy is a little girl learning English as a first language. When she speaks she usually doesn’t pronounce the /r/ sound well. For example, she might say "gwapes" instead of "grapes". She can hear the difference between the /r/ sound and other sounds though.