Stroking a cat or a dog for 10 minutes can significantly reduce your stress, suggests new research. Scientists studied 249 students to look at what happened when they stroked one of the animals. It was known that stroking cats or dogs can boost your mood, but now there is real research to prove the physiological effects of doing so. The team from Washington State University found that there were huge reductions in the stress hormone cortisol from just 10 minutes of interaction.