We present data from a between-student study on student response to questions
on Newton's Third Law given throughout the academic year. The study, conducted
at Rochester Institute of Technology, involved students from the first and
third of a three-quarter sequence. Construction of a response curve reveals
subtle dynamics in student learning not captured by simple pre/post testing. We
find a a significant positive effect from direct instruction, peaking at the
end of instruction on forces, that diminishes by the end of the quarter. Two
quarters later, in physics III, a significant dip in correct response occurs
when instruction changes from the vector quantities of electric forces and
fields to the scalar quantity of electric potential. Student response rebounds
to its initial values, however, once instruction returns to the vector-based
topics involving magnetic fields.Comment: Proceedings of the 2010 Physics Education Research Conferenc