The photochemistry of the rotor probe 9(2carboxy2cyanovinyl)julolidine (CCVJ) was studied to elucidate a curious effect of fluid flow previously reported. The apparent sensitivity to fluid motion observed in CCVJ but not in the closely related molecule 9(dicyanovinyl)julolidine (DCVJ) is found to be an indirect effect of a photoisomerization reaction.