The dried root of the manioc species Manihot anomala, known as sienejna, is used by the Ayoreo Indians of Paraguay to initiate a naijna (shaman), allowing communication with the spirits.
Not all of the Ayoreo believe that this plant works, however it is said that the shaman feels effects similar to drunkenness when sienejna is smoked. In this state, the spirits of the animals (especially those of iguanas, poisonous snakes, and birds) meet him in the shape of small people so that they may let him know of their whereabouts.
Smoking experiments, however, have not revealed any type of hallucinogenic or other psychotropic effect. Further study is required.