There is widespread agreement within the scientific community and multiple disability advocacy organizations that FC is not a valid technique for communicating with those with autism spectrum disorder. Instead, research indicates that the facilitator is the source of the messages obtained through FC (involving ideomotor effect guidance of the arm of the patient by the facilitator). While proponents say that FC should never involve guiding the patient, researchers attending an FC class in 1993 observed that physical force was used to prevent the patients from moving their hand away from the keyboard. Facilitators may also influence movements without realizing it. Researcher Gina Green stated: "Very subtle influence can affect people's behavior. It doesn't even have to be touch. It can be the slightest sound, the slightest visual cue." Guidelines for facilitators instruct practitioners to expect the emergence of hidden skills and sensitive personal information, to use anecdotal data to validate authorship, to avoid objective scrutiny.