  Covariational reasoning -- reasoning about how changes in one quantity relate
to changes in another quantity -- has been examined extensively in mathematics
education research. Little research has been done, however, on covariational
reasoning in introductory physics contexts. We explore one aspect of
covariational reasoning: ``goes like'' reasoning. ``Goes like'' reasoning
refers to ways physicists relate two quantities through a simplified function.
For example, physicists often say that ``the electric field goes like one over
r squared.'' While this reasoning mode is used regularly by physicists and
physics instructors, how students make sense of and use it remains unclear. We
present evidence from reasoning inventory items which indicate that many
students are sense making with tools from prior math instruction, that could be
developed into expert ``goes like'' thinking with direct instruction.
Recommendations for further work in characterizing student sense making as a
foundation for future development of instruction are made.
