Variation theory says that learning consists in coming to discern differences in an object of learning that were previously unnoticed. We are thus learning to see an object in new ways. We can never see a thing simply as what it is - we always see some aspect of it, against a background and as compared with other things.

learning to see something in a certain way amounts to discerning certain critical features of that phenomenon and focusing on them simultaneously. [Marton and Trigwell, Variatio est mater studiorum, p. 393]

According to variation theory, variation is a necessary condition for learning:

The thesis we advocate is that we discern, or learn to see, that which varies. Without variation there is no discernment, no learning at all. [Marton and Trigwell, Variatio est mater studiorum, p. 393]

Dialogism, as applied to learning, would hold that learning is appropriating others’ words, through which we aquire new ways of expression. Appropriation is not simply copying others’ use of words but of making them one’s own, giving them “our-own-ness” using them creatively to one’s own intentions.

Our speech, that is, all our utterances (including our creative works), is filled with others’ words, varying degrees of otherness or varying degrees of “our-own-ness” ….These words of others carry with them their own expression, their own evaluative tone, which we assimilate, rework, and re-accentuate. [Bakhtin, Speech Genres, p. 89]

I argue that discerning features amounts to being able to articulate (or express in some way) differences. Hence variation theory and dialogism about learning are compatible. Appropriating ways of expressing entails appropriating ways of seeing and acting. For example, in mathematics classrooms, when a phenomenon is considered, within any classroom “there will be a range of ways in which the phenomenon is seen and understood by students.” In this case, variation is introduced by helping students experience “how” their own understanding varies from that of their peers and that of canonical mathematical ways of describing the phenomena.

The question about variation theory is to what extent an experience of variation is sufficient for learning. I believe that dialogue is usually essential, that is, it’s not enough to just “see”, one also has to articulate and think and experience how others experience the phenomena.

References:

Bakhtin, M. M. (1986). Speech Genres and Other Late Essays. University of Texas Press. Marton, F., & Trigwell, K. (2000). Variatio est mater studiorum. Higher Education Research & Development, 19(3), 381–395.