Is the distinction between the two prepositions motivation of a person for an action or are they interchangeable?
a student has written "the motivation of the study is" and I would suggest "the motivation for the study was". Am I right?
Are you saying I should transform the whole sentence?
Is the student's version: The motivation of/for this study was to observe the differences regarding this subject among adults.
any better like this: "The second study was aimed at finding the difference among adults in that respect."