All mediums and directors of mediumship sessions must be aware of, and know how to recognize, the phenomena of animism.  Animism is a state of trance provoked, unconsciously and unintentionally, by the Spirit of the medium, via the property of expansion of his perispirit, without any intervention from another Spirit.  As the author Martins Peralva writes, "Many times, that which appears to be a mediumistic trance, with all the appearances of the influence of a Spirit, is nothing more than the medium, naturally a maladjusted medium, reliving scenes and events extracted from his own subconscious mind, a phenomena which is provoked by the magnetic contact, meaning the approach of entities with whom the medium shares experiences of the remote past.  In phenomena of animism, the medium expresses himself as if there were truly a discarnate Spirit there to communicate"

Animism is provoked by the fixation of the mind on some circumstance, a state in which a being, incarnate or discarnate, sees nothing, hears nothing, and feels nothing outside of that situation.  Isolating himself from the world around him, such an individual begins to concentrate his thoughts and energies around his own misbalance, crystallizing himself in time. At some point in time, the Spirit is able (most likely with the help of others and the transpiring of events) to free himself from this self-captivity.  However, later on, at some time in the future, the memory of that fixation could resurface in the form of animistic phenomena.  Peralva writes "The crystallization of our mind on given situations today, can provoke the future manifestation of animistic phenomena, just as such a crystallization or fixation of the mind at some time in the past can exteriorize itself in the present."

Though such phenomena may not be evident at the start, since it does present the same appearance as a truly mediumistic communication, it can be recognized over time, as the director(s) and members of the mediumistic group find that that particular medium's communications begin to repeatedly display the same characteristics and revolve around the same type of situation, emotions and thoughts. 

How should a case of animism be handled once discovered?  Peralva explains; he writes (also quoting, in part from Andre Luiz's book, "In the Domains of Mediumship")

"The medium, in those conditions, should be treated with the same attention that we administer to the suffering Spirits that communicate.

For that reason the directorship of mediumship work requires, without a doubt, much love, comprehension, and patience-- virtues that, together, result in what the instructors classify as << Fraternal Touch>>, so as not to hurt or offend those who find themselves in such conditions.

If the director of mediumistic sessions does not have a sincere good-will, we believe that a medium in his group will receive little or no benefit.

The medium inclined toward animism is a defective vessel that can be fixed and restored to full service through the director's understanding, or destroyed by his lack there of.

Readjusted, patiently, with the resources of evangelic charity, the medium can be transformed into a valuable work partner. Misunderstood, he could become a victim of obsession." 

As you can see, the potential for the phenomena of animism presents another reason why the teachers of the Doctrine advise their students that the development and exercise of mediumship should be done at the appropriate place, which is a responsible and serious Spiritist Center, under the support and guidance of a knowledgeable and benevolent director.

Schubert, Suely Caldas. "O Transe Mediunico" [The Mediumistic Transe]. Mediunidade: Caminho Para Ser Feliz [Mediumship: The Path to Happiness]. Votuporanga- SP, Brazil. Casa Editora Espírita "Pierre-Paul Didier". 1999. 110.  

Peralva, Martins. "Animismo" [Animism]. Estudando A Mediunidade [Studying Mediumship]. Rio de Janeiro-RJ, Brazil: Federação Espírita Brasileira [Brazilian Spiritist Federation].1998 (20th ed). 186-190.

Peralva, Martins. "Fixacao Mental" [Mental Fixation]. Estudando A Mediunidade [Studying Mediumship]. Rio de Janeiro-RJ, Brazil: Federação Espírita Brasileira [Brazilian Spiritist Federation].1998 (20th ed). 191-192.

Kardec, Allan. "The Action of The Medium In Obtaining Spirit Manifestations." The Mediums' Book. 2nd ed (1st edition FEB). Trans. Anna Blackwell (translated 1876). Ed. Livraria Espírita Allan Kardec. Brasilia-DF, Brazil:  Federação Espírita Brasileira [Brazilian Spiritist Federation}. 1986. 238-239.