You may be thinking: Hold up. Love is such a personal thing, how can anyone possibly measure it? Tashiro explains that psychologists have been attempting to do just that for the past 50 years or so. “It’s not perfect,” he says, “It started out using self-reported measures, asking people how much they loved somebody, say on a scale of one to 10. Now, it’s still self-reported, but we also have brain imaging studies, hormonal evidence, and there’s all kinds of data that we can bring to bear about whether someone is in love with someone else.”