Marton and Booth’s Theory of Variation (1997) is drawn from the phenomenographical research tradition. According to Marton’s Theory of Variation, discernment of critical features occurs under systematic interaction between a learner and the thing to be learnt, and variation is the agent that generates such interaction (Marton, Runesson, & Tsui, 2004).
Phenomenography argues that individuals understand phenomena in the world differently because experience is always partial.
This requires teachers to engage closely with their students to grasp the variations in understandings and knowledge so they can take account of this diversity in structuring the learning activities in a lesson (Marton & Tsui, 2004).
Variation, therefore, is a primary factor in encouraging student learning.
Variation theory sees learning as the ability to discern different features or aspects of what is being learned. It postulates that the conception one forms about something or how something is understood is related to the aspects of the object one notices and focuses on.
The application of the Theory of Variation has become increasingly popular in Lesson Studies.
Variation theory argues that the most effective way to help students understand a concept is to focus on providing opportunities for students to experience variation in the features of the concept that they currently take for granted (Marton and Tsui, 2004).
Marton and Tsui (2004) specify four patterns of variation were proposed: contrast, generalization, separation and fusion. They form the kernel for discernment under variation.