Consider this study: A New York Times article published on April 24, 2007, reported the research of Dr. Giorgio Vallortigara, a neuroscientist at the University of Trieste, Italy, and his two colleagues. The researchers asked whether a dog wags its tail in a preferred direction in response to positive stimuli and in another direction in response to negative stimuli. To answer their question, they recruited 30 dogs that were family pets. Filming each dog from above, they allowed it to view (through a slat in its cage) three positive stimuli separately, in order of descending positivity: its owner, an unfamiliar human, and a cat. All the dogs responded by wagging their tails to the right. But when the dogs were presented with an unfamiliar, aggressive dog, a negative stimulus, all dogs wagged their tails to the left. Which of the following statements is the research hypothesis for this study?

a. A dog's tail will wag differently in response to positive stimuli and to negative stimuli. b. A dog's tail will wag more to the left in response to positive stimuli and more to the right in response to negative stimuli. c. A dog's tail will wag more to the right in response to positive stimuli and more to the left in response to negative stimuli. d. There will be no difference in a dog's tail wagging while viewing positive and negative stimuli.