With 100 different cats, he rubbed the plant matter on a sock or a square of carpet, and set the material in the cats’ line of sight. Then he waited. If the cat approached and backed away, he considered that a denial. “Animals tend to move towards things they like, and back away from things they consider threats,” says Buffington. After each success or denial, he’d wait about five minutes for the cat to relax, then try again with another plant type. The response rate was striking: Almost 80 percent of the cats responded to the silver vine (a higher response rate than even nip, which got less than 70 percent of the cats high), and roughly 40 percent each for valerian root and honeysuckle.The kicker is that these other plants do not contain nepetalactone. Read about research into cat euphoria at Wired.