The title of this piece is a bit misleading; really I discovered aizuchi as a child, though if someone had said the word to me I probably would have said 'Bless you'.
It sounds exotic, but 'aizuchi' is the Japanese name for something very common, namely the polite interjections in conversations which demonstrate attention and understanding: the 'yeah's and 'uh huh's that we use to show another person that we're on the same wavelength as them.
Most cultures use aizuchi to some extent and it is an important part of human relationships and conversations. The correct use of aizuchi can be pivotal in determining a conversation's 'success'. Too many interjections could be perceived as rude by some cultures, whereas too few could offend the speaker, by suggesting that the listener has switched off. However, aizuchi is a particularly important linguistic and cultural phenomenon in Japan. The word is part of a proverb 'aizuchi o utsu' (あいづちをうつ) which literally means 'striking the forge hammer'. The phrase describes the rhythmic to-and-fro of two smiths striking a hammer; as linguist Laura Miller describes it 'the alternating strikes of a mallet by a blacksmith and his apprentice'. The blacksmith makes a strike and his apprentice responds, in the same way that in a conversation one person often leads, while the other reassures the speaker that his words are understood.
Crucially in Japanese culture, aizuchi is not the same as agreement. The listener says 'yes' to indicate comprehension, not necessarily agreement. However, it is easy for non-native Japanese speakers to confuse aizuchi with agreement, as I discovered at first hand during my weeks teaching Japanese school children and collaborating with their Japanese teachers.
When not teaching, the other English teachers and I were expected to organize activities for the children, for instance sightseeing in London and Oxford. Once the students had seen Big Ben, Westminster, Buckingham Palace etc, we thought it would be nice for them to spend a day in London Zoo, to coincide with a lesson on animals. The zoo seemed to us good 'school trip' potential, and a safe place in which to let 70 Japanese children wander around and have fun. We mooted our plan to one of the Japanese teachers who spoke English, and were pleased when after every suggestion we made he said 'yes, yes, yes'. 'That's settled then', we thought, and promptly booked 70 tickets to the zoo.
Feeling happy with ourselves, we mentioned to the teacher a few days later that we were excited for the zoo, at which point he said, 'um, I've been thinking, maybe zoo, but maybe not zoo. Maybe National Portrait Gallery?' Knowing a little about Japanese culture (enough to know that the word 'no' is rarely used, but is instead implied) I quickly realised that his 'maybe not zoo' equated to a polite but resounding 'no'. The other English teachers and I could not understand his apparent volt-face, that is until I stumbled upon this article (http://www.tofugu.com/2013/06/25/aizuchi/) and reassessed our conversations mindful of aizuchi. The teacher had never wanted to go to the zoo in the first place, but from our Western perspective we assumed that his aizuchi were marks of approval, and agreement.
The situation resolved itself happily in a compromise: our zoo tickets were not wasted and we were able to see other sights on the same day, and importantly, we English teachers left with a better understanding of Japanese conversational customs.