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A new study reports two studies exploring the effects of streaks in symptom checklists on perceived personal disease risk. In the context of these studies, a streak is a sequence of consecutive items on a list that share the characteristic of being either general or specific.  

The study was conducted with Virginia Kwan of Arizona State University, Sean Wojcik of the University of California, Irvine, Talya Miron-shatz of Ono Academic College, Ashley Votruba of ASU, and Christopher Olivola of the University of Warwick- appears in Psychological Science, a journal of the Association for Psychological Science.

Participants perceived a higher personal risk of having an illness when presented with a checklist in which common symptoms were grouped together than when presented with a checklist in which these same symptoms were separated by rare symptoms. This research demonstrates that something as arbitrary as the order in which symptoms are presented in a checklist can affect perceived risk of disease.

The researchers identify a psychological mechanism underlying the effect of streaks in a list of symptoms and show that the effect of streaks on perceived risk varies with the length of the symptom list. The findings reveal a tendency to infer meaning from streaks in medical and health decision making. 

Surveying cancer-related sites, they discovered that these vary in the way they present common and mild-or "general"-symptoms and more specific and serious ones. To test how streaks affect risk perception, students were presented with lists of six symptoms of a fictional kind of thyroid cancer ("isthmal"). 

One group got three general symptoms (such as fatigue and weight fluctuation) followed by three specific ones (e.g., lump in the neck); another the reverse order; and the third group a list alternating between general and specific. 

Participants checked off symptoms they'd experienced in the previous six weeks and then rated their perceived likelihood of having the cancer. The first two orders yielded similar risk ratings. But the ratings were significantly lower when the list alternated.

A second experiment compared lists of 12 or 6 symptoms, this time for a real cancer, meningioma. The three orders were the same as in the first experiment. The effect of order disappeared for the longer, but not the shorter, list-that is, the influence of streaks was diluted when the list was longer. It's possible that even if a participant checked a series of symptoms-leading to suspicion of disease-boxes left unchecked offered reassurance of to the contrary, the authors think.

The findings could prove useful for public health education, Kwan says. "With certain types of illnesses, people tend to seek medical attention at the latest stage." Meanwhile, "people also go to doctors asking all the time about illnesses that are very rare."  To encourage people to seek earlier health screenings, grouping common and mild symptoms might be wise. To limit overreaction, the rare ones should top the list. Reaching particular populations is also a public health challenge.