Chapter 4 authors: C. Sue Carter and Stephen W. Porges

Introduction

Social cohesion has been fundamental to the success of mankind; it could very well be the main factor that sets us apart from our less successful Neanderthal cousins, who often failed to creative viable social groups. Despite humanity’s sociability, though, challenges such as war and rapid population growth can present obstacles to cooperation.

Biological Origins of War and Peace

Emotions and mental states associated with aggressive behavior—whether they be defensive or strategic—are central to an understanding of war and peace.

Working Hypotheses and Assumptions

Evolution and Development

Human responses to adversity—based on adaptation via evolution—can be described by activity in the hypothalamic-pituitary-adrenal (HPA) axis. Differing experiences over a long period of history lead to the observation that the current human population exhibits varied behavioral responses to positive and negative conditions.

Genetics, Epigenetics, and Behavior

Human behavior is, at least in part, influenced by inherited genetic codes that have been selected by evolution over time. Moreover, the human genome can actually be altered physically and functionally by behavioral experiences.

Short- and Long-Term Perspectives on Neuroplasticity and Adaption

Parts of the human nervous system are more plastic and adaptable than others. Evolutionarily older components like the brainstem, for example, are less capable of adaption. In the short-term, adaptions may seem advantageous in the face of adversity. But in the long-term, chronic stress and negative experiences can be costly.

Neuroendocrine Perspectives on Mammalian Social Behavior

The Social Nervous System

Neural structures and mechanisms form the basis for behavior that leads to affiliation, selective social attachment, empathy, and other prosocial behaviors. The “social engagement system” refers to the biological and behavioral capacity for both positive social behaviors and positive physical and behavioral reactions to threats.” This system can inhibit automatic fight-or-flight behaviors.

Automatic Nervous System and Physiological Adaptions Linking Sociality and Health

The autonomic nervous system is necessary for vegetative and growth processes, aiding in survival and reproduction. In a safe environment, the autonomic nervous system might elicit positive social behaviors. In an unsafe environment, it might elicit defensive or aggressive behaviors.

Mammalian Reproduction and Motherhood Shape the Nervous System

In the whom, the placenta provides vital nutrients to offspring, and the paternal and maternal genomes contribute to the growth and size of the offspring. Growing up, children learn rapidly and in various ways, benefiting greatly from maternal investment, social synchrony between caretakers and children, and family or group living.

Maternal Behavior as a Prototype of Social Behavior

Oxytocin and vasopressin, the hormones that facilitate birth and lactation, allow mothers to communicate with their babies socially and via the endocrine system.

Oxytocin and Vasopressin Pathways

Properties and Functions of Oxytocin

Oxytocin is a hormone believed to be associated with positive sociality and human contact, and it may directly or indirectly influence other neural systems involved in positive social engagement.

Ties that Bind

It is unknown whether or not humans can form social bonds in the absence of oxytocin. With mothers and children, oxytocin may help to protect both mother and infant from the memory of the pain associated with childbirth, thereby promoting attachment. Moreover, maternal oxytocin may protect against post-partum depression.

Oxytocin Facilitates Growth and Healing

Oxytocin can affective restorative processes, which might explain the well-documented association between social support and prevention of or recovery from many illnesses.

Properties and Functions of Vasopressin

Vasopressin is a hormone associated with active forms of coping and defense. Primitive functions include water retention, and more modern functions might be increased social “bravery.”

Interactions between Oxytocin and Vasopressin

Oxytocin and vasopressin interactions can have mixed results. In some conditions, as with emotional arousal, the behavioral effects of the release of oxytocin and vasopressin can be opposing. Under other conditions, the effects can be similar, as noted in initial encounters among prairie voles.

The Effects of Oxytocin Are Not Always Prosocial

The effects of oxytocin can differ dramatically depending on factors like genetics, context, and social history. For instance, without a supportive rearing experience, the effects of exogenous oxytocin on an individual may no longer appear prosocial or positive.

Developmental Consequences of Oxytocin and Vasopressin

Oxytocin helps protect the brain and heart from hypoxia, especially during birth, and the hormone also shapes the physical development of the brain. Prairie voles exposed to exogenous vasopressin exhibited increased aggression in adulthood.

Sex Differences and Psychiatric Implications of Oxytocin and Vasopressin

While there is a need for more research on the effects of medications and gender on both oxytocin and vasopressin, some evidence suggests that sex differences in the vasopressin system may have consequences for male-biased disorders like autism and early onset schizophrenia. Women experiencing schizophrenia displayed an association between higher levels of oxytocin and fewer psychotic symptoms; in a separate study, women experiencing a psychotic episode displayed higher levels of vasopressin.

Methodological Limitations

It is difficult to address real-time interactions between biochemical changes and social behavior, so future research should have as its goal an understanding of naturally occurring mechanisms that regulate biological mechanisms.

Questions and Challenges for Future Research

In the future, research should try to address methodological issues such as expanding the scope of research from the individual level to the group level; biological measurement issues such as improving the detection and extraction of peptides; issues pertaining to the differences between individuals and sexes; and issues related to modeling with animals and humans.

The Promise of Formative Childhoods

Peptide pathways strongly influence human behavior from birth to adulthood, and formative childhoods are perhaps the best route to peace.