Joseph Weizenbaum wrote a famed conversational computer program. What is the program called?

The chatterbot was created in 1966. This computer program presented a simulation of an interview with a psychotherapist. The interview was based on the technique of active listening: it let the patients speak about their problems without restraint. It was even able to provide people with some advice (to formulate a response). Some of the program's patients couldn't believe that they had a dialogue with a bot!