In his 1991 work titled The Interaction Hypothesis: A Critical Evaluation, Rod Ellis discusses Long’s version of the interaction hypothesis and proposed some revisions based on studies and other academic interpretations of the hypothesis that were available at the time. Notably, he introduces a revised version of the hypothesis, which is characterized as: (1) Comprehensible input is useful for learners but is neither necessary nor sufficient for L2 acquisition; (2) Acquisition is made possible via input modifications (i.e. negotiation of meaning) but only if the learners both comprehend the input and are able to adopt differences into their own output; (3) Interaction situations that force learners to modify their output promotes their L2 learning. This revision is based on the lack of direct evidence supporting the original hypothesis, but that indirect evidence is nonetheless adequate to maintain some level of the theory. Additionally, this revision would allow the theory to be tested empirically, since it more clearly defines the relationship between acquisition, comprehension, and input.
