When faced with a decision, we read restaurant and movie reviews and ask friends to recommend plumbers and dentists because it’s easier than gathering all the information ourselves. But this tendency to follow the crowd has broad social implications—even affecting human health, according to Juanjuan Zhang, associate professor of marketing at the MIT Sloan School of Management.

Sometimes that downside is no more serious than the failure of a good yet unpopular restaurant, but Zhang has found that the tendency to act based on what others do—observational learning—also applies to the decisions being made by patients on the kidney transplant list. The result has been the loss of viable organs.

In the United States, kidneys are allocated on a first-come, first-served basis and potential recipients know their place on the waiting list. So, when a kidney is offered to the fifth person in line, he knows that four people have already refused that kidney. He doesn’t know why—everyone has the same information on donor age, gender, and health status—but Zhang found organs are disproportionally rejected simply because other people have declined them. A bias has developed.

“If I know that I’m on the bottom of the waiting list and all of a sudden they offer me a kidney, I can infer that people above me already said no,” Zhang says. “People may say no because they didn’t have time for the transplant that week or they were sick. But that information’s not communicated.”

As the kidney is offered to one potential recipient after another, crucial time passes (a cadaveric kidney must be transplanted within 72 hours)—leading to the loss of about 10 percent of donated kidneys each year in the United States. “Individual decisions aggregate into social behavior,” says Zhang, who investigated the transplant data for her PhD dissertation at the University of California Berkeley.

While marketing experts like Zhang more often examine decisions about consumer products, the fundamental questions apply equally to the organ market, she says. “Hospitals provide organs and the patients choose, and they don’t always choose based on the same criteria.”

Understanding observational learning has public policy implications as well, according to Zhang, whose recent research centers on the hot topic of whether to label foods as deriving from genetically modified organisms (GMO). Currently, 70 percent of US foods fall into this category, with no labeling required. But, several states have considered mandating GMO labeling.

Zhang surveyed shoppers and discovered that even proposing a mandate affects public opinion. “[The proposal itself] is sending a negative signal, a sort of social stigma,” she says. “People’s perception of GMO safety is lower once we give the impression of mandatory disclosure.”

The bottom line, Zhang says, is that actions can have unexpectedly significant societal consequences—which is why it’s so valuable to study human behavior. “From the purely scientific perspective, we just want to know why things happen in the way that they’re happening,” she says. “We always talk at a high order about social behaviors, but no matter what we observe in the end, that’s coming from individual decisions.”

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