Dr. Guthrie and Felis domesticus or: tripping over the cat.
The principal reactions described in Guthrie and Horton's classic learning monograph appear to have been caused by the mere presence of the experimenters. Neither escape nor food reinforcement is necessary for the establishment of such responses. They are species-typical "greeting" reactions, readily elicited by the sight of human observers.
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D002415:Cats / Q000502:physiology*; D003216:Conditioning, Operant / Q000502:physiology; D006801:Humans; D013239:Stereotyped Behavior / Q000502:physiology