The black tufted-ear marmoset is helping the psychobiology lab of Dr. Jeffrey French at UNO understand the ways in which social interactions can positively influence health and well-being.

Stressing the Familiar

by Teresa Gleason and Michael Rukstalis

January 2005

It sounds like an ad pitch from a telephone company: if you're stressed out, the familiar sounds of your significant other's voice can calm your nerves.

In reality, it's the latest research study from the psychobiology laboratory of Jeffrey French, the Varner Professor of Psychology and Biology at the University of Nebraska at Omaha (UNO).

In the study, reported in the January 2005 issue of the scientific journal Hormones and Behavior, UNO graduate research assistant Michael Rukstalis and Dr. French tested this "reach out and touch someone" idea in marmoset monkeys.  The team tested whether familiar monkey calls could reduce levels of ‘stress' in marmosets temporarily isolated from their long-term pair mate. 

Male and female marmosets, small tropical primates about the size of a common squirrel, form strong attachments, or ‘pair bonds,' with their partners.  During times of stress, the physical presence of a marmoset's pair mate is calming and actually reduces physiological indicators of stress, a process often referred to as social buffering.  In addition, marmosets are also well known for possessing individually specific, or ‘signature' vocalizations.  In other words, marmosets can distinguish each other, much like humans, based on sound alone.

In order to investigate if these vocalizations could also reduce stress, adult marmosets were temporarily isolated from their long-term pair mate and exposed to three conditions – one in which they heard recorded calls from their social partner, one in which they heard calls from an unfamiliar marmoset and one in which the monkeys heard nothing.    

Levels of stress were monitored by analyzing the concentrations of cortisol in urine samples.  Cortisol, known as the stress hormone, is produced by the adrenal glands in response to stress – be it physical, environmental, chemical or even emotional. 

The team's results confirmed that isolation from significant social partners is associated with a short stress response – levels of cortisol were almost three times higher than normal levels.  However, when marmosets were isolated and heard their partner's calls, the stress response was reduced by one-half. 

Not just any voice will do, though.  Stress levels were not reduced in marmosets who heard calls recorded from a stranger. 

"Our results provide the first evidence that a monkey call associated with a specific individual – a significant social partner - can decrease the magnitude of a physiological stress response.  This is a process we refer to as ‘vocal buffering' of the stress response," Rukstalis said.  "Since humans also show social buffering of stress responses, this study contributes to our understanding of the ways in which social interactions can positively influence human health and well-being. Further, since one of the goals of Dr. French's research is to promote the captive breeding of this primate that is threatened with extinction, the research will help our group and others design optimal social environments for these efforts."

Dr. French's lab employs techniques he developed for monitoring physiological stress responses using noninvasive sample collection methodologies.  In the past, these measures could only be made by collecting blood samples, a process that itself can be a great source of stress for both the research animal and scientist.  However, the marmosets in Dr. French's lab are trained to provide urine samples in exchange for a treat, a procedure that is decidedly not stressful, Rukstalis noted.

The research in Dr. French's lab is supported by grants from the National Institute of Health and the National Science Foundation.  Dr. French currently serves on the Neuroendocrinology, Neuroimmunology and Behavior Study Section within the National Institutes of Health's Center for Scientific Review.  Since 1991, his lab at UNO has focused on the black tufted-ear marmoset, one of South America's endangered species.

For more information, contact Dr. French at 402.554.2558 or jfrench@mail.unomaha.edu, or Rukstalis at 402.554.3094 or mrukstalis@mail.unomaha.edu.

Teresa Gleason is director of communications at UNO.  Michael Rukstalis is a graduate research assistant at UNO.