https://www.sciencedaily.com/releases/2018/05/180529132128.htm

Pet owners are familiar with the challenges of figuring out what their pets want. Building on Pavlov's work teaching his dogs to associate the ringing of a bell with food, researchers have tried to understand how animals and humans react to rewards under different circumstances. However in the real world, what constitutes a reward and how this may motivate behavior are rarely clear.

Writing in PLOS Computational Biology, a team of scientists at Kyoto University's Graduate School of Biostudies report how worms evaluate a potential reward, examining their reactions by studying their movements.