Memory is an often overlooked but after non-conscious brain activity, such as the respiratory and pulmonary system, it is mankind's most powerful cognitive ablility. Answers to questions such as, "Who are you?" are usually put together with a string of memories. There are many techniques to improve memory such as the memory palace and batching - the process of putting 3-4 numbers together in rhythm (like a phone number). Humans memory ability is linked directly to imagination. When asked to recall certain events, humans visualize the event in their heads and rely on past auditory stimuli to prepare their response. If a person has ingested a mind-altering, psychoactive substance, their memory is often judged to be inaccurate or unreliable.