time perception. However, the neurochemical basis of psilocybin's effects on the perception of time are not known with certainty. Users having a pleasant experience can feel a sense of connection to others, nature, and the universe; other perceptions and emotions are also often intensified. Users having an unpleasant experience (a "bad trip") describe a reaction accompanied by fear, other unpleasant feelings, and occasionally by dangerous behavior. In general, the phrase "bad trip" is used to describe a reaction that is characterized primarily by fear or other unpleasant emotions, not just transitory experience of such feelings. A variety of factors may contribute to a psilocybin user experiencing a bad trip, including "tripping" during an emotional or physical low or in a non-supportive environment (see: set and setting). Ingesting psilocybin in combination with other drugs, including alcohol, can also increase the likelihood of a bad trip. Other than the duration of the experience, the effects of psilocybin are similar to comparable dosages of LSD or mescaline. However, in the Psychedelics Encyclopedia, author Peter Stafford noted, "The psilocybin experience seems to be warmer, not as forceful and less isolating. It tends to build connections between people, who are generally much more in communication than when they use LSD." Group perceptions Through further anthropological studies regarding "personal insights" and the psycho-social effects of psilocybin, it can be seen in many traditional societies that powerful mind-active substances such as psilocybin are regularly "consumed ritually for therapeutic purposes or for transcending normal, everyday reality". Positive effects that psilocybin has on individuals can be observed by taking on an anthropological approach and moving away from the Western bio-medical society; this is aided by the studies done by Leary. Within certain traditional societies where the use of psilocybin is frequent for shamanic healing rituals, group collectives praise their guide, healer and shaman for helping alleviate them of pains, aches and hurt. They do this through a group ritual practice where participants, or just the guide, ingests psilocybin to help extract any "toxic psychic residues or sorcerous implants" found in one's body. Group therapies using classic psychedelics are becoming more commonly used in the Western world in clinical practice. This may continue to grow as long providing the evidence remains indicative of safety and efficacy. In social sense, the group is shaped by their experiences surrounding psilocybin and how they view the plant collectively. As mentioned in anthropologist article,