Why do learners – in the same essay – sometimes make an error in the use of a specific target-language structure and sometimes they don’t?

Teenage girl (16-17) lying on bed, writing, close-up

This morning, whilst correcting Spanish essays written my year 8 students (12-13 year olds if you are not familiar with the British school system) one mistake attracted my attention : a girl had written – on the same line, but within different sentences – ‘llevé una camiseta’ (I wore a T-shirt) and ‘llevo una camiseta’ (I wear a T-shirt) to mean, in both cases, ‘I wear a T-shirt’.  When asked to self-correct, she noticed her mistake immediately and changed the ‘é’ in ‘llevé’ to ‘o’ (a sign that she had declarative knowledge of the first person of the Preterite and Present in Spanish).

But why would a student produce the present tense correctly in one sentence and not in another within the same essay? And how could my year 8 student get the verb right on the second instance when she had just got it wrong a few words before on the same line?

As I often do in my one-to-one corrective conferences, I asked the student in question why she thought she had made that mistake. She shrugged and said: “No idea, sir’. Maybe I was tired”. A plausible explanation considering that she had written a long essay and that the error occurred in last paragraph. But how can tiredness cause such mistakes?

The answer to this question relates to what applied linguists call Interlanguage Variability, a widely documented phenomenon that causes frustration to a lot of teachers but which is actually a developmental feature of L2 acquisition. What is Interlanguage variability? What causes it?

To fully understand this phenomenon, the reader will benefit from getting acquainted with two important concepts: Interlanguage and Spread of Activation. I will take for granted that the reader is familiar with the concept of Working Memory, already explained in some detail in a previous post (see below: “Why do our learners get prepositions, articles and verb and adjectival agreement wrong?”). Please note that in what follows I will focus only on the cause of variability which, in my view, are more relevant to teachers operating in explicit foreign language instruction settings and that I will not venture into sociolinguistic theories of the likes of Labov’s nor into nativist accounts of the phenomenon.


Interlanguage is the name given by Selinker (1972) to the internal representation the L2-learner builds of the target language system in his/her Long Term Memory. How does s/he build it? Mainly through hypothesis-testing, often using his/her dominant language as a reference framework in an attempt to decode and make sense of the target foreign language. Since L2-acquisition occurs through trial and error, Interlanguage is not an exact system, but rather an approximation of the target language system one is acquiring.

It should be noted that the cognitive and affective feedback the learner receives from the target language speakers/knowers plays a pivotal role in the construction of the Interlanguage system, as it will ultimately determine which Interlanguage forms will be automatized and acquired. So, if a given Interlanguage form receives a lot of positive cognitive and affective feedback from the environment, it will eventually be internalized after the brain will have repeatedly been given reassurance that it is accurate.

What often happens, though, during the early stages of L2 acquisition, is that learners do not always receive consistently negative/positive cognitive or affective feedback on their errors; and even when they do receive it, it doesn’t necessarily follow that they will internalize it. This happens for a number of reasons to do with the corrective approach used in the classroom (e.g. selective or no correction); its quality (e.g. ambiguous feedback); strong interference from their first language which makes the Interlanguage structure more resistant to correction; etc.

Moreover, when students engage in unmonitored L2-production (in or outside the classroom), as happens in the course of unstructured communicative activities, their output is likely to contain more errors.

Although errors made at this stage are not automatized immediately, they will not be discarded by the brain straight away either, especially when they are repeated several times – and errors due to L1 transfer are likely to occur quite frequently at the early stages of L2 learning.  Hence, it is very common for the Interlanguage of an L2 learner to ‘contain’ more than one representation of a given target language structure: the correct one and one or more incorrect ones. Example: ‘I went’ in French is ‘je suis allé’, however, L2 students often say ‘j’ai allé’ at the early stages of French acquisition because they overgeneralize the dominant way of forming the Perfect Indicative in French. These two forms ‘j’ai allé’ and ‘je suis allé’ often coexist in L2 learners’ of French Interlanguage and compete with one another for retrieval. I will come back to this example. Now with this in mind let us look at the concept of ‘spread of activation’.

Spread of activation and Variability from processing inefficiency

When we are attending to a task, like forming the Perfect tense of ‘Aller’ in French, as in the above example, Working Memory will have to retrieve from Long-term Memory the correct match for ‘I went’ in French. As Working Memory attends to this tasks, every single bit of information (lexis, grammar, imagery)  related to the concept ‘I went’ stored in our Long Term Memory gets activated. ‘Electrical impulses’ run through semantic memory’s neural networks and the information or ‘nodes’ along the network get more or less activation based on the strength of their associations with the proposition we mean to ‘translate’ into French – the so-called ‘fan effect’. The items along the activated neural networks which will receive the greatest activation will be ‘‘j’ai allé’ and ‘je suis allé’ and, possibly, in my experience, ‘j’allé’. Which one of the three forms will be retrieved and used in the written/oral performance will depend on the ‘weight’ of each form (i.e. the strength of the memory trace) and on the context.

If the learner knows the correct French translation of ‘I went’ and Working Memory is not experiencing cognitive overload thereby having enough free space to monitor the output, even though s/he might have an initial moment of indecision due to the concurrent activation of the other two activated forms, s/he will be likely to apply the correct Interlanguage form. However, if his/her Working Memory is experiencing cognitive overload (processing inefficiency) due to a challenging task-in-hand, in the absence of close monitoring, any of the three forms may be retrieved (pretty much randomly) if their ‘weights’ are more or less equivalent. Hence the importance, at the early stages of learning, not to engage in overly unstructured oral or writing tasks.

Variability as caused by formulaic language

Variability can also be caused by formulaic-language learning that is to say the acquisition of unanalyzed chunks or set phrases memorized without really knowing what each constituent of the phrase actually means or how the grammar rules which ‘holds’ them together actually work. Thus, if a learner uses ‘je suis allé au cinema’ correctly in a written piece because s/he has learnt that sentence as an unanalyzed chunk, it will not mean that s/he masters the use of the Perfect Tense of verbs requiring the auxiliary ‘Etre’ in the Perfect Tense. Hence, when, a few lines below, in the same essay, s/he translates ‘I went’ incorrectly in a different context (e.g. I went to the park) we should not be particularly surprised by the occurrence of variability.

Variability as caused by learner strategies

Variability can also be caused by the learner’s attempt at testing a specific hypothesis they formulated about a given target language structure. Let us look at Muskaan’s hypothesis-testing strategy. Muskaan is a year 9 student of Spanish I teach who, today, told me that when she is not sure whether her assumptions about how to use a given structure are correct, tries them all out deliberately in order to get feedback from me as to which one is correct. In the essay we were marking together today, for instance, she had used a conditional and an imperfect form to translate two very similar sentences which should have required the imperfect. She wanted to tested the hypothesis that, just like in English you would use the conditional tense in sentences like “when I was young I would play the guitar in my free time’ one can do the same in Spanish. In Muskaan’s case, the retrieval of the two concurrent Interlanguage forms is not automatic / subconscious, but is triggered by a deliberate risk-taking strategy.

Risk-taking is another frequent cause of variability in our learners’ output and a phenomenon that must not be discouraged as it has great potential for learning.

In conclusion, Variability is a complete normal phenomenon that should not cause us too much frustration, even when it seem to be caused by our teaching. The most important implication of this phenomenon for the MFL classroom is that we need to be cognitively empathetic with our learners when we find this kind of mistakes and while addressing them through appropriate remedial learning, we must not stigmatize them. Secondly, teachers must give students enough time to monitor their output and encourage them to edit their written work carefully and in ways which lessen the cognitive load on their Working Memories (as the problem which triggered the error in production is likely to hinder its detection whilst proofreading). One such strategy is to have several runs through the same text, each one aimed at checking a particular type of item at a time (e.g. first time, adjectival agreement; second time, verb agreement; third time, omissions of copulas; fourth time ‘small function words’). Sentences that are particularly long and require complex processing should be dealt with by investing more time and focus.


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