"They collected 1000 narrative reports and mined the text for common words using machine learning techniques. Having identified signature words, they then tested their hypothesis by seeing whether the results could be used to accurately predict which drug the reports referred to. Ecstasy reports tends to use words such as "club", "hug", "rub" and "smile", which reflect the social setting in which the drug is often used and the feelings of love and friendliness the drug seems to produce. Coyle was able to accurately identify Ecstasy reports almost 90% of the time. LSD and magic mushrooms are both associated with words such as "see", "look", "saw", "room", "tell", "ask", "walk", "house". DMT and Salvia are associated with words such as "reality", "dimension", "universe", "state", "consciousness", "form", "entity". These clusters of words allow speculation about the receptors and signalling pathways in the brain that the drugs target." http://arxiv.org/abs/1206.0312 - Adriano