B. distinguishes between two types of back-channel signals. Affirmative signals that encourage the speaker to go on the way he has planned like 'true', 'sure', 'exactly', 'I see', etc. are called 'non-steering signals'. Signals like 'really', 'honestly', 'nonsense', 'indeed' etc. that show that the hearer wants to change the content of what the speaker says are called 'steering signals'.