Llama owners will tell you that their pets have a sixth sense about people who are needy, ill or frail. Carol Rutledge says that her therapy llama, whose name is Knock, will walk voluntarily to the bedside of a hospice patient and stand in silence while the patient reaches for him. “It wrenches at your heart,” she said. “It’s taken me several visits to be able to get through it without getting emotional.”

Mona Sams, an occupational therapist in Roanoke, Va., has eight llamas and five alpacas at her practice, which serves children with autism and other disorders, as well as adults with developmental disabilities. One patient is a girl with severe cerebral palsy and seizures who comes twice a week. “I have one llama,” — named Woolly — “who literally sits there with her for a whole hour, face to face,” Ms. Sams said. “She calls Woolly her ‘counselor,’ and she will spend the first part of the hour telling Woolly what difficulties she’s had, and he just sits beside her for that entire time.”

Ms. Sams is the lead author of what seems to be the only published study involving the use of llamas as therapy animals. The article, published in 2006 in the American Journal of Occupational Therapy, describes a very small clinical trial in which children with autism were given either standard occupational therapy or therapy that involved handling llamas. The results “indicated that the children engaged in significantly greater use of language and significantly social interaction in the occupational therapy sessions incorporating animals than in the standard occupational therapy sessions,” the study authors wrote.

Hal Herzog, an anthrozoologist and professor emeritus of psychology at Western Carolina University, said that such results are not surprising, though they do not prove the efficacy of animal-assisted therapy. He says there’s a big mismatch between what the public believes — or wants to believe — about the effectiveness of therapy animals and what scientific studies show.