When i was in Europe for an official work, i had to discuss some business details with the operations department. I went to their cabin and i was listening to their requirement. The person had completely explained the detailed and i was shaking my head as i was listening to her and i was able to understand what she wanted. Once she completed explaining, she looked at me and then again started explaining again. I thought she wanted to stress her point and hence repeating the requirement. I was again shaking my head.
She looked at me and asked “Did you understand?”.
I told her “Yes, continue to the next requirement”.
Then she asked me “then why are you shaking you head as NO”.
When i was shaking my head i was shaking it left to right and then to right to left. She understood that as ‘No, i did not understand” and hence she repeated the statement.
Indians mostly shake their head left –right as an acknowledgement. Where as rest of the world they shake their head up-down fashion to acknowledge. So Indian going abroad shake your head correctly but foreigners coming to India do as you do in you country otherwise this will create another confusion.