Rewire Me has run dozens of articles on people’s conscious journeys toward healthier, deeper, more spiritually attuned ways of living. I’ve written about religious experiences that are so powerful they seem to spontaneously rewire the whole person, transforming him or her into not just a better person but a completely new one. Such rebirths, I’ve noted, are often marked with name changes: from Jacob to Israel or Saul to Paul. But religious conversion isn’t the only reason people change their names. Some of the best-known name changes of our era have involved changes in gender, from George Jorgensen to Christine Jorgensen, from Tracy Langondino to Thomas Beatie (who gained tabloid attention a few years ago when he became the world’s first pregnant man). What happens in the brain and the mind when gender presentation is aligned with how a person has always felt?

The animal kingdom is one place to look for insight into this question. For some species, sex changes are part of the ordinary cycle of life. Justin Rhodes, Ph.D., a neuroscientist and professor of psychology at the University of Illinois, has been conducting a long-term study of clownfish (also called anemonefish), the colorful fish that live in symbiotic partnerships with sea anemones in the warm shallows of the Indian and Pacific oceans. (Nemo of Pixar fame was an Ocellaris Clownfish, or Amphiprion ocellaris. Some 30 other species have been identified.)

All clownfish are born with testicular and ovarian tissue and hence with the potential to be either female or male. Each clownfish group has one dominant female; when she dies, over a period of months the largest male changes his sex and takes her place.

As Dr. Rhodes relates in an illuminating YouTube video, the change is precipitated by a social cue (the disappearance of the female) but is orchestrated by the brain. The hypothalamus sends a signal to the pituitary gland, which releases hormones that cause the testes to absorb, the ovaries to develop, and the fish’s behavior to change. As the process gets under way, the fish’s brain literally rewires itself.

“We can measure and track neurogenesis,” Dr. Rhodes says. “We can see what areas of the brain are sprouting new neurons or what areas of the brain are removing neurons. We also have different techniques to study plasticity…certain genes are expressed when a cell is undergoing a lot of genomic changes. And we now have developed the capability to measure the different proportions of ovarian and testicular tissue, [as well as] which neuropeptides are being released from the pituitary gland [and] signaling to the gonads to change. We can discover then, in this one dramatic example, how the social environment reorganizes behavior and presumably makes some inferences about how something similar might happen in other organisms.”

Does something similar happen when a human being decides to switch genders—when a Bradley Manning transitions to a Chelsea Manning or a Chastity Bono becomes a Chaz? The best answer appears to be “no.”

“The general public seems to be inordinately hung up on genital surgery and has all but equated it with a gender transition,” Kaplan told me. “Actually, a very small subset of transsexuals has surgery as part of the transition. Most transitions consist of a ‘social transition’ and then hormones and, in the case of male to female, facial hair removal, voice training, perhaps some cosmetic surgeries.” Unlike clownfish, the vast majority of human beings aren’t hermaphroditic, either physiologically or figuratively. Most people’s sex (as in whether they are born with ovaries or testicles, a penis or a vagina) lines up with their gender (the attributes and behaviors that are culturally attributed to males and females). Gender is not a physical attribute, in this sense, but a kind of Platonic idea that can be abstracted from the physical substance (the body) that it usually expresses itself through.

The biologist Anne Fausto-Sterling has written extensively about “intersexual” people who, due to accidents of physiology, exist on a continuum between female and male. In a famous paper she published in The Sciences in 1993, she argued that “biologically speaking, there are many gradations running from female to male; and depending on how one calls the shots, one can argue that along that spectrum lie at least five sexes—and perhaps even more.” She cited the case of Emma, a fully functioning hermaphrodite who had grown up as a female but could and did have “normal” sex with people of both sexes. “My husband supports me well,” she purportedly told the Johns Hopkins urologist Hugh H. Young, who had offered her surgery, in the 1930s, “so I think I’ll…stay as I am….Even though I don’t have any sexual pleasure with him, I do have lots with my girlfriends.”

For those who are born with one set of sex organs, gender tends to be a matter of either/or rather than neither/both. But for a significant cadre of people, their bodies and their genders don’t match up. “You can’t choose your gender identity any more than you can choose your sexual orientation or being right- or left-handed,” Ami B. Kaplan, a New York City-based therapist who specializes in gender issues, told me. “However, you can choose your gender expression (how you’re going to present) or who you sleep with or which hand you eat with. It may be more or less comfortable depending on how in-synch it is with your true orientation, and if it’s out of synch it can be uncomfortable to the point of suicide for some people.”

“For a human being, the subjective experience of gender—something that only exists in the mind—is so strong that some people feel the need to change their bodies to conform to it. In that sense, a “sex change” is more of an affirmation of what has to be than a conversion to something else.” “‘Gender dysphoria,’” Kaplan continued, “is an extremely uncomfortable state of unease with one’s physical body. The other problems are social—stigma, discrimination, ignorance.” Some transgender people, she adds, “remark after their transitions that they wouldn’t have changed anything and that being transgender has given them a whole new perspective….But it’s a small subset.”

In this light, sexual conversion isn’t a rebirth as a new person—it’s a correction, a realignment that brings one’s inner and outer personas back together. It needn’t be a surgical correction, either.

“The general public seems to be inordinately hung up on genital surgery and has all but equated it with a gender transition,” Kaplan told me. “Actually, a very small subset of transsexuals has surgery as part of the transition. Most transitions consist of a ‘social transition’ and then hormones and, in the case of male to female, facial hair removal, voice training, perhaps some cosmetic surgeries.”

It is a bit paradoxical and hard to grasp. The brain of the little clownfish is so plastic that it can reorganize both itself and its whole body. But for a human being, the subjective experience of gender—something that only exists in the mind—is so strong that some people feel the need to change their bodies to conform to it. In that sense, a “sex change” is more of an affirmation of what has to be than a conversion to something else.