According to Vygotskian Socio-Cultural Theory (SCT), dialogue is the basis of all learning including language learning. Language Acquisition Device is situated in dialogue, not within one's head according to SCT. Social interaction leads to development of complex intramental activities. That is, what happens between people leads to development of what happens inside oneself. Therefore, we observe that children progress from object-regulation to other-regulation to self-regulation.
In language learning thus, learners first express their new learning (linguistic forms and functions) in interactions with others, and later they internalize them for independent use. Here, tasks have opportunities to help learners interact in various situations and use different language structures and functions. This will equip learners to use these independently later. Therefore, use of language in collaboration with others will lead to use of use of those and more complex language independently. Tasks are therefore tools for developing collaborative learning activities.
Vygotsky's Zone of Proximal Development (ZPD) implies that there is an actual and potential level of development. It is the potential level that is activated while learner communicates in collaboration with others. Later this potential will be actualized when the learner can independently use complex language. ZPD conceptually looks like the i+1 of Krashen.
In ZPD, the interlocutors create a conducive and comfortable language level and atmosphere where communication takes place. This is what adults do when they take out their child-talk with children. The same is used by teachers in classrooms. It is like an adjustment of levels. There is collaborative construction of discourse or dialogue within ZPD. Tasks can do exactly this. They create an optimum context/zone for communication/language exchange.
For tasks to be able to create ZPDs and promote language development, they must have a meaningful activity in it, participants must interpret the task in similar manner, their goals must be the same, they must have co-ownership of the task's activity and there must be a meaningful outcome to be achieved, which is perceived by the participants.
