Assume that the two traits for the stimuli are T_1 and T_2. The decision basis is not the extent of correlation between them, but rather their causal relationships with the stimuli. Firstly, what is the effect of interest in this context? Secondly, among the three variables (stimulus, T_1 and T_2 ), determining which causes which is of utmost importance? For a more general discussion, see here.
Gang Chen