Dr. Harold Levinson has looked deep into the human psyche and has discovered that there may be no need to look that deep after all. A great number of phobias, mood disorders and learning disabilities, he says, are all just a simple problem of the inner ear.

This may come as a surprise to a majority of the world's psychiatrists and scientists, who have looked instead to Freud or to neurotransmitters, for example, to explain problems such as agoraphobia or dyslexia. But Levinson holds his ground."Ninety percent of all phobias that show up in psychiatrist's offices and 98 percent of all learning-disabled kids have inner ear problems," says Levinson, who was in Salt Lake City recently to promote two new books on the subject.

Levinson has impressive credentials. With a background in both psychiatry and neurology, he is an associate professor of psychiatry at New York University Medical College and is director and founder of the Medical Dyslexia Treatment Center in Great Neck, N.Y.

He says he first began to suspect the culpability of the inner ear when he was hired by the New York City Board of Education in the 1960s to work with learning-disabled kids. In those days, he says, it was believed that learning problems - trouble learning to read or spell, speech disorders, lack of concentration - were emotional problems.

"After examining literally a thousand of these children," says Levinson, "I found that at least 75 percent had a history of balance and coordination problems. They were usually late walkers and talkers. They had difficulty with large and small motor coordination."

All this data seemed to point to physiological problems, and the common denominator seemed to be that these are functions that are controlled by the cerebellar-vestibular system, or inner ear.

The inner ear system provides the body with both sensory processing and motor processing. Levinson likens it to the fine-tuning mechanism on a TV set - the inner ear makes sure that things like light, sound, motion, air pressure and chemical information entering the brain are tuned just right. It also fine tunes all the motor information leaving the brain, guiding and coordinating our eyes, head and limbs in time and space.

If the inner ear isn't working properly - perhaps as a result of an infection, a concussion, whiplash, pregnancy or surgery - the result may be a host of problems, says Levinson.

He began to realize the extent of those problems, he says, when he started treating his learning-disabled patients with simple anti-motion sickness medicine. The patients not only showed improvement in learning, he says, they also reported that they were no longer afraid of elevators or snakes or the dark, or a whole catalog of other phobias.

Other problems also began to clear up, he says, including hyperactivity, impulsivity, obsessions, moodiness, and psychosomatic symptoms such as headaches, dizziness and rapid heartbeat.

According to Levinson, 75 percent of the learning disabled and phobic patients he has treated with anti-motion sickness pills have shown "significant improvement."

About four-fifths of these patients no longer need to take any medication after four years, he adds. Most will notice some changes within hours or within several days. Most patients, however, will have to try several types of medication before finding one that works.

But Levinson stresses that no one should be his own doctor. "No one should treat himself or herself, regardless of whether medications can be bought without a prescription," he emphasizes in his new book, "Phobia Free." Both this book and a companion book, "Smart But Feeling Dumb" are available in paperback.

Aware that there might be skepticism about his theories, Levinson emphasizes that the concept and treatment are "completely supported" by Sir John Eccles, Nobel Laureate in inner ear neurophysiology, "as well as by a majority of neurotologists, who are ear, nose and throat physicians specializing in inner ear dysfunction." One of these, says Levinson, is Dr. Howard P. House, President Reagan's personal physician.

Levinson has set up to national hotlines to answer questions about his inner ear insights: 800-334-READ and 800-8PHOBIA.