All current behavioural evidence suggests that protein-dependant memory processes (i.e. ITM-intermediate term memory and LTM-long-term memory) occur in series. That is, LTM (altered gene-activity and new protein synthesis) formation depends on prior formation of ITM (new protein synthesis required). Using environmentally relevant stressors (predator detection and crowding) that alter memory formation in the pond snail, Lymnaea stagnalis, we show, for the first time, that ITM and LTM are formed in independently; that is in parallel. Separately, stress resulting from predator detection enhances LTM formation; while stress from crowding blocks LTM formation. In each instance, ITM is also present. However, there are emergent properties when stressors are presented in combination with each other. Stress from the presence of predator scent and crowded conditions experienced in combination block ITM but allow the formation of both short-term memory (STM) and LTM. Since the molecular processes leading to ITM and LTM are highly conserved across species, these data suggest that the parallel formation of ITM and LTM may be a fundamental biological process.