Most research on the flipped classroom employs group-based interactive learning activities inside
the classroom, citing student-centered learning theories based on the works of Piaget 1967 and
Vygotsky[79]. The exact nature of these activities varies widely between studies. Similarly, there
is wide variation in what is being assigned as "homework". The flipped classroom label is most
often assigned to courses that use activities made up of asynchronous web-based video lectures
and closed-ended problems or quizzes. In many traditional courses, this represents all the instruction
students ever get. Thus, the flipped classroom actually represents an expansion of the curriculum,
rather than a mere re-arrangement of activities. A simplified depiction of this is shown
in Table 2.