When a group of people hear the same story or watch the same video, their heart rates tend to rise and fall in synch. This correlation of heart rates, described this month in Cell Reports, could one day lead to new tools for measuring attentiveness, both in the classroom and the clinic.
Lucas Parra, a biomedical engineer at City College of New York, knew from a previous work that people paying attention to the same videos or listening to the same stories show similar brain activity, as measured by electroencephalogram (EEG). His colleague Jens Madsen convinced him that the heart deserved a look as well, the German News Agency reported.
"Brain signals are hard to get. If the heart can do that, it is even better because you don't have to set up complicated recording equipment for the brain," says Parra.
The pair teamed up with co-senior author Jacobo Sitt of the Paris Brain Institute in France and others in a series of experiments to explore how heart rates increase and decrease across listeners.
They began by asking over two dozen volunteers to each listen to 16 one-minute segments of Jules Verne's "20,000 Leagues Under the Sea" and recorded the results. The heart rates of participants, captured by electrocardiogram (EKG), tended to speed up or slow down at the same points in the story.
The team then showed another set of volunteers a series of five short educational videos on topics ranging from the immune system to how light bulbs work. They then asked volunteers to watch the same videos a second time, but with the added distraction of attempting to count backwards silently in their minds while viewing. Without the distraction, viewers' heart rates were correlated much like in the first study. With the added math challenge, attention waned and heart rates fell out of sync.
The research also found that people whose heart rates most closely correlated with others were better at recalling details such as the names of characters.
