As twin studies have helped to show in the past, rarely is a trait purely genetic or only a product of a person’s environment—more often, it’s a blend. A person’s genes can shape their environment in meaningful ways, and vice versa. This interplay further blurs the lines of how we inherit or acquire traits. Epigenetics obscures that line even further in that specific genes can be turned “on” or “off” and cause variation in traits even among identical twins.
Nevertheless, Reed hopes to trace twin-to-twin variation in the kokumi study back to a particular gene or receptor by mapping the pairs’ preferences for the kokumi-seasoned popcorn onto their genomes. “We look to see where the differences in the DNA might map onto extremeness of kokumi perception,” Reed says. “So for instance, of the people who can really taste it—are they more likely to have a particular genotype and a particular gene?”
Most traits are multigenic and rely on several genes, rather than just one or two. But thanks to surveys from Twins Days, Reed and her colleagues have honed in on a few genes that contribute to specific tastes. The bitterness of brussels sprouts, for example, has been linked to a receptor called TAS2R38, and Reed followed the bitterness of basil back to a receptor called TAS2R60.
“Twins are useful for just getting an idea of, is this a heritable genetic trait and is it worth pursuing in a more in-depth and detailed way?” Breslin says. “It's a very useful first step.”
Geneticists aren’t the only researchers who find a bounty at Twins Days. In a tent near Reed’s, a team from West Virginia University snapped photographs of 360 twins through conventional, infrared, and 3-D cameras. The data will be used by developers to tweak facial recognition software.
“If we can make facial recognition that works well for twins, it should work well for the general population,” says Jeremy Dawson, the team leader and a biometric researcher at West Virginia University. He says current software used in security systems or smartphones still has a hard time distinguishing between mothers and daughters, let alone identical twins.
Meanwhile, Shannon Weitz, a scientist from Proctor & Gamble, ushered 140 sets of identical twins into a trailer for research that will help develop her company’s line of Olay Professional skin care products. She took photos of the twins and recorded their facial measurements. Then, each twin completed a survey on routine habits like sun exposure and hydration. Weitz will pick the twin that looks youngest in the photos and use their survey results to identify which habits may have helped them stave off signs of skin aging.
It’s tough work, mining for all this information at a bustling festival in the heat of summer. The teams frenetically process twins and data to the point of exhaustion, scarcely stopping to eat or drink during 15-hour shifts. “It's about as intense a thing as I've ever done,” Breslin says. The weather, too, can be a problem—in the past, Reed tried to include herbs in her taste trials, but has since abandoned that idea because “Twinsburg is just too hot to try to keep everything fresh.”
And of course the twins are there, first and foremost, to enjoy themselves. “People show up to test with you on taste, after having just had a hot dog that has mustard and relish and ketchup and onions on it and it just makes things difficult,” Breslin says. “Some people might be a little tipsy."
Breslin says it’s all worth it in the end. “We generate incredible volumes of data and we always party when it's over,” he says. “We're so happy to have the data, and we're so happy to be done with it.”
Given the disparate discoveries that can be made by studying twins, the demand for research booths at Twins Days—which the festival caps at 16 per year—isn’t likely to subside for 2015’s 40th annual celebration. "We could probably fill up the whole place with research if we wanted to," says Miller, the festival’s organizer. “But that’s not what Twins Days is about.”