Was the russian physiologist who demonstrated that neutral aspects of the environment can attain the capacity to evoke responses through pairing with other stimuli and that bodily processes can be influenced by environmental cues.

Danilo has been working for metropolitan taxi for three months. he expected that his job would be to drive around the city, pick up fares, and drop them off at their desired locations, but in his first few days on the job he realized that the job entails much more. he must keep his taxi cab clean and neat, and some days he will be stationed at the shop and go to people's houses to pick them up and bring them to the local airport. within a few months, he has learned that taxi drivers often express frustration with the people they call "civilians"—that is, non–taxi drivers, whose driving skills they complain about incessantly. in his first few months on the job, describes what danilo is undergoing.