Book Review: The Chemistry Between Us, by Larry Young

Review and Interview by James Burkett

Originally published Spring 2013.

sulcus128Love is the one area where we are all scientists: even though we all engage in it to some extent, and we all have some knowledge about it, most of us will freely profess our ignorance. Even those of us who study behavioral neuroscience find that information flying out the window when we see our lover’s face. Can powerful, yet insubstantial emotions be explained by chemical reactions in the brain? Dr. Larry Young certainly thinks so. In his new book, “The Chemistry Between Us: Love, Sex, and the Science of Attraction,” Dr. Young and his co-author Brian Alexander delve deep into the science and the experience of love, sex, desire, and infidelity, presenting the topics in their full complexity and cutting through the controversies using what is known from decades of research on the brain.

Dr. Young’s research lab at Emory resides at the Yerkes National Primate Research Center, although it is by no means limited to primates. His projects are surprisingly broad in scope, focusing mainly on the neural substrates of social attachments in monogamous prairie voles, but also including human and non-human primates, as well as rats and mice. His research ranges from developing PET ligands, to transgenics and optogenetics, to genomics, to animal empathy. Researchers in his lab seem able to dream up any project they like, so long as they have the drive to master the requisite techniques and skills.

mind-reviews-the-chemistry-between_1In this book, Dr. Young makes the case that complex behaviors and emotions are driven by chemical processes in the brain, and in many cases we know quite a bit about those processes. He leads us stepwise through the evolutionary garden, where genes, hormones, life experience, and brain circuitry impact our sex, gender, personality, and desires, as well as our ability to resist those desires. Yet, the book is by no means sterile and clinical; the science is weaved into a series of stories, provocative and accessible and yet informative and surprising.

He opens by showing us the science behind sex, gender, and gender preferences, and the critical periods in development where hormones influence them. Yet he does so through a series of fascinating examples, such as the machihembra from the Dominican Republic, individuals who are born female and yet transform into fully functional males at puberty. He discusses the secrets of how female behavior, preferences, and even odor subtly change over the course of ovulation – and how males somehow detect and respond to these changes, particularly when they are at the strip club. He also talks about the objective irrationality of deciding to have children. When some (roughly half) of us eventually do become mothers, some aspects of maternal instinct are inborn – such as the innate attraction to infants that seems to appear magically during pregnancy – while others are a (perhaps unconscious) result of early life experience, such as empathy and the feeling of reward derived from motherhood.

Dr. Larry Young, Ph.D.
Dr. Larry Young, Ph.D.

Dr. Young then discusses some of the most famous theories from his field – that bonding in females is derived from brain circuitry for maternal care, while bonding in males is derived from brain circuitry for territoriality. Along the journey, we learn about oxytocin and vasopressin and the suite of behaviors to which each is related across a wide range of animals, along with a few other surprising hypotheses – for instance, why human men have large penises and human women have large breasts compared to other animals. We also learn how biology and genetics conspire against sexual fidelity – and how natural and common infidelity really is. Finally, Dr. Young explores the surprisingly faithful parallels between love and addiction, and how drugs of abuse release the same neurochemicals involved in human attachment.

The book is hilarious, graphic, blunt, sometimes crass – but always entertaining. The stories are intricate and yet complete and coherent; intriguing and funny yet based on pure evidence. The text is heavy with humor and science, though sometimes light on philosophy, creating the occasional split between a person’s biology and their identity, while blurring the lines between evolution and psychology. The book will fascinate and enthrall you while it educates you.

I had the opportunity to interview Dr. Young regarding his book.

INTERVIEW:

JPB: What inspired you to write this book? What was your goal in writing it?

The monogamous prairie vole
The monogamous prairie vole

LJY: The biggest inspiration was the research that I have been doing ever since graduate school. It started when I was a PhD student at the University of Texas working with lizards. I realized that I could manipulate their sexual behavior very exquisitely just by giving them one hormone, estrogen or testosterone. As I came to Emory studying the voles, I was again astonished and fascinated to see how individual molecules could affect behaviors as complex as pair bonding. I wanted to share that science with people who are not necessarily behavioral neuroendocrinologists, but who may be interested in how the brain creates sexual desire or love. I wanted to convey to people who are interested in science and even the lay public the principle that the mechanisms that are involved in controlling animal behavior are also playing a similar role in humans.

 JPB: How can we, as scientists, take control of the media narrative surrounding our work? Without each of us publishing our own book, that is.

LJY: When scientists write a manuscript, they should always think about, what is the public interest in this paper? Why would a non-scientist be interested in this? Then talk to the PR representatives from the University or your institution, the people who know how to get the media’s attention, and put together a press release. Don’t be bashful about trying to get your work out there. It is our job to convey to the public the importance of science, and that means reaching out to the press and communicating with them when we have things that are of public interest.

 JPB: In the book you present two parallel hypotheses regarding human bonding: that bonding in females is an extension of maternal behavior; and that bonding in males is an extension of territoriality. Are these hypotheses primarily evolutionary, or do you think they extend into human psychology as well?

sulcus178LJY: They are primarily evolutionary. In the book we present these as two mechanisms of pair bonding in monogamous animals, and the relevance of this to humans is more speculative. In the evolution of new behaviors, what the brain tends to do is tap into systems that already exist for other things and tweak them a little bit. Oxytocin, which is responsible for promoting labor, for ejecting milk when the baby nurses, for maternal bonding to the baby, this same molecule is involved in bonding the female to the male. The same thing is true for males and territorial behavior. Vasopressin is involved in scent marking, aggression, and territoriality, and in voles it’s also involved in mate guarding, protecting his female partner. It’s almost as if the female has become an extension of his territory, and he will aggressively defend that female against other animals. Human males don’t think of their female partner as their territory; women don’t think of their husbands or lovers as babies; but there is that root in the biology.

JPB: In light of the studies you discuss showing that OT underlies some aspects of maternal care, what do you think of recent work showing an increase in OT in children from administering OT to parents?

LJY: That is really fascinating work that suggests that the engagement of the parents with the offspring can really stimulate the OT system. That stimulation occurs when the mother and baby, or father and baby, are having reciprocal social interactions. That stimulates the OT release, making that social interaction more reinforcing and helping to build social skills and social aptitude. It builds the brain’s knowledge of how it interacts and relate to others. This system may somehow be disrupted in diseases like autism, and these individuals can’t develop the social skills and the social reciprocity that typical kids may have. If this data is true and can be replicated, this highlights the importance of engagement of the parents or caregivers with the baby in terms of facilitating the normal development of the social brain.

JPB: In Tristan and Isolde, Wagner said that love is a sometimes-fatal chemical imbalance; and in your book you make the case that love is an addiction. If love is truly an addiction, should we be using preventative medicines when going on first dates?

LJY: No, I don’t think so, because if you do that then maybe you’re going to miss the person who’s really the perfect match for you, your soulmate. If I would have done that on my first date with my wife, maybe we wouldn’t have the wonderful life that we have together. You never know when you’re going to meet that right person and when your brain’s real chemistry is going to be kicked off to create that love. You’re right that sometimes when people fall in love, it leads them to do things that they definitely regret later, even things that everyone around them can look at and say, “why in the world is he doing that? It makes no sense.” Nonetheless, his brain neurochemistry is telling him that this is the right thing to do. But the critical thing is that sometimes that crazy thing turns out to be the right thing to do. You meet that special person that you will be really happy with the rest of your life. I would hate for someone to miss out on that because they are afraid of falling in love.

JPB: What new research are you performing along the lines of the hypotheses you present in your book?

LJY: One important aspect of our work is not so much about the neurobiology of love but how we can use our knowledge of the chemistry of social relationships to improve social functioning in social cognitive disorders. For example, in autism, schizophrenia, and some other psychiatric disorders, there is an inability to relate to others and an inability to engage in social reciprocity. We are figuring out how to exploit neurochemistry to improve social functioning and maybe to teach social skills to those who lack them. For example, we are exploring the possibility of combining OT treatment with behavioral therapies so that we can teach social skills to autistic subjects. So that’s one really important application, going from the preclinical basic science to clinical applications. That’s really the goal of the Center for Translational Social Neuroscience that I started here at Emory. But we’re also doing some other things that are very interesting. For example, we are looking at the neurobiology of consoling behavior. When the partner is injured, prairie voles for example will show increased grooming to the partner, maybe to relieve their stress. We’re exploring the neurobiology and the role of oxytocin and vasopressin in that consoling behavior. This may give us insights into the evolutionary origins of things like empathy, which we all think of as a human trait. Empathy, like love, has its origin in animal behavior.

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