Visions spark debate
In “Visions for all” (SN: 4/7/12, p. 22), researchers found that functioning people who “hallucinated” God were high on the “absorption” scale and that 4 percent of people studied reported hallucinations.

This reminded me that 4 percent of the population is grade V hypnotizable. All of these superhypnotizable people rate very high on absorption. [As a psychiatrist,] I had patients like this who had been severely abused as children. These are the ones who developed multiple personalities, or dissociative identity disorder. These patients often had visions of helpful spirits. Since none of your sources seemed to recognize that dissociation in healthy grade V hypnotizable people can show this kind of picture, I thought I would bring it to your attention.
Ralph B. Allison, Paso Robles, Calif.

If I didn’t know better, I would say this article, though interesting, seems to have as its goal to reduce God to a hallucination at best and psychosis at worst. There are crucial differences between hallucinations (at least in my experience) and God speaking: Hallucinations occur in times of mental stress, drugs or illness that affect the mind; hallucinations are bizarre, otherworldly auditory and visual sensations; hallucinations do not make moral judgments or render valid insights.
Kenneth V. Hoffman, South Kingstown, R.I.

Neandertal DNA still a mystery
“Icy isolation may have led to new human species” (SN: 4/7/12, p. 5) was the best and most concise article about human ancestry that I have ever read. Yet, by focusing on “cold-climate refuges,” it neglects one area: the human groups that never left Africa. The only information I have seen is that the modern ancestors of these folks have no trace of Neandertal or Denisovan DNA in their genomes. What do we know about the evolution of humans that remained in warm climates?
Gene Phillip, Great Falls, Va.

Geographical variation among populations today in amounts and types of Neandertal DNA is poorly understood. But look for research on this topic to heat up. — Bruce Bower

A question of magnetism
“Sleeplessness agitates the brain” (SN: 4/7/12, p. 16) says, “To look for signs of altered brain function, the team delivered a jolt of magnetic current to the participants’ skulls that kicked off an electrical response in the nerve cells.” I believe the phrase “jolt of magnetic current” is not accurate. The experimenters used transcranial magnetic stimulation, or TMS, which functions by applying to the skull a rapidly changing magnetic field.
Robert P. Yassanye, Sarasota, Fla.

The reader is correct. — Laura Sanders