The finding refines how scientists study animal happiness Researchers use tickling to study the biology of animal happiness. A new study shows differences in how rats like to be tickled. " data-large-file="https://www.sciencenews.org/wp-content/uploads/sites/2/2026/05/050626_HT_tickling_main.jpg?w=800"> Researchers use tickling to study the biology of animal happiness. A new study shows differences in how rats like to be tickled. Janet Stephens/Wikimedia Commons For nearly a decade, Vincent Bombail has been tickling rats. It’s been a standard technique used in the study of animal happiness . But not all rats particularly enjoy the experience, data show. Female rats prefer gentler, more playful tickling than males, Bombail and his colleagues report April 15 in Biology Letters . The findings suggest that the same physical experience evokes a different emotional response in different individuals, potentially influencing the results of studies on animal happiness.…