learners vary their use of language similarly. They are more likely to use the correct target-language forms in formal contexts and non-target forms in informal contexts.
Another important factor that accounts for the systematic nature of variability is the psycholinguistic context-whether
learners have the opportunity to plan their production. To illustrate how this works we can turn again to Jean. The transcript on page 16 is of the oral narrative that Jean produced after he had been given the chance to write it out. The transcript below is of another oral narrative which Jean produced, this time with no prior opportunity to plan. A comparison of how Jean marks verbs requiring past tense in the two narratives is revea ling. First, it is
clear that overall Jean uses a higher proportion of irregular verbs like 'saw' and 'went' in the unplanned narrative than in the planned one. Second, Jean is much more likely to mark verbs correctly for past tense in the planned than in the unplanned narrative.
This is true for both regular and irregular verbs but especially so for the latter. In fact, in the unplanned narrative he fails to mark a single regular verb for past tense. It is clear that Jear's use of the past tense is strongly influenced by the availability of planing time. He is more likely to use target-language forms when he has time to plan.