While Young- Helmholz  theory of trichromatic colour vision makes clear some of the processes involved in how we see color, it does not explain all aspects of color vision. The opponent-process theory of color vision was developed by Ewald Hering. These two theories were competing till a way was found to combine the two theories in the dual-process colour transduction theory (Knoblauch, 2002).

Your null hypothesis is that there is no difference between your competeing theories and your H1 is that there is

and then you show how to combine the two to answer your problem! Good luck!

Your question made me think of the classic paper by Platt. Here is the reference:

Platt, J. R.  (1964). Strong inference.  Science, 146, 347-353.

It is well worth reading. It may provoke you to think about research hypotheses in creative and important new ways.

Thank you! I will read it!

I thought of one other thing. You have two variables, X and Y. Call X at time 1 is X1 and Y at time 1 is Y1. At time 2 the variables are X2 and Y2. Do you have enough data at both points in time to run two regression analyses?

In one regression analysis, you regress Y2 on X1 and Y1. In the other, you regress X2 on X1 and Y1.

Your printout from SPSS or SAS would inform you X1 is a significant predictor of Y2 (adjusting for Y1) and if Y1 is a significant predictor of X2 (adjusting for X1). I think such an approach could help you.