For doctors and nurses, hand hygiene is supposed to be as intuitive as breathing. But is this behavior really second-nature, or do health care workers need supervision to keep their hand cleaning habits on target?

A new study out of Santa Clara Valley Medical Center (SCVMC) in San Jose, California, suggests that even doctors may fall prey to what is known as the “Hawthorne Effect” -- whereby people change their behavior when they know they’re being watched.

The study, being presented this weekend at the Association for Professionals in Infection Control and Epidemiology (APIC) conference in North Carolina, found that hand hygiene compliance at SCVMC differed dramatically when health professionals knew they were being evaluated, versus when they did not.

Because infection-causing bacteria are often carried from patient to patient on the hands of health care workers, breaking this chain of transmission is a top priority in hospitals nationwide. But this study -- and many others -- indicate that while the principle of hand hygiene is simple, human behavior is one of the hardest things to change.

Hidden Observers

The researchers at SCVMC had two types of auditors assessing hand hygiene: Infection Prevention (IP) nurses, who everyone in the hospital recognized as the hygiene patrol, so to speak, and high-school and college-aged volunteers who were trained to perform the exact same assessments, but who were not consistently recognized as such by hospital staff.

As the study progressed, one pattern grabbed the researchers' attention.

“[We noticed] a very consistent trend that our Infection Prevention nurses were seeing something different than what volunteers were seeing,” Maricris Niles, an infection prevention analyst at SCVMC, told ABC News. Specifically, the IP nurses noted much higher compliance rates.

The researchers wondered whether it could be that compliance was being recorded differently by different observers. Extra measures were taken to ensure that this was not the case. What it came down to, it seemed, was the Hawthorne Effect.

“When we would come on the floor, I would notice that the nurses or providers were not using the alcohol,” Lisa Hansford, one of the recognizable IP nurses at SCVMC, told ABC News. “Then they would glance up and see me and bend over backwards to lather up.”

The investigators found the hand hygiene compliance rate observed by IP nurses was about 57 percent, while hospital volunteers -- who tended to blend in and not be recognized as hygiene auditors -- recorded rates of about 22 percent. While this phenomenon has been noted before, the team at SCVMC was surprised by the stark gap--and they have launched a series of interventions to try and drive their compliance rates higher and higher.

Clean Hands Count

Poor adherence to hand hygiene has been a longstanding issue. According to the U.S. Centers for Disease Control and Prevention, health providers clean their hands less than half of the time they should, and the World Health Organization reports averages as low as 40 percent.

Another study being presented at APIC from the Henry Ford Health System in Detroit found that hand-washing rates improved after hospital staff members were shown images of millions of bacteria found on common surfaces. Appealing to human emotions -- like disgust -- seems to have had a meaningful impact.

On May 5, the CDC launched a “Clean Hands Count Campaign” to promote hand hygiene adherence in hospitals. Part of their mission is to empower patients to hold healthcare workers accountable for cleaning their hands.