The research was conducted on more than 150 bees in Wageningen University's bio-veterinary research laboratory. The scientists trained the bees by giving them a treat — a sugar-water solution — every time they were exposed to the scent of a mink infected with COVID-19. Each time the bees were exposed to a non-infected sample, they wouldn't get a reward (a process known as Pavlovian conditioning). Eventually, the bees could identify an infected sample within a few seconds — and would then stick out their tongues like clockwork to collect the sugar water.