What I asked was; What is trading sentiment? I can understand that trading sentiment is the levels of optimism or pessimism present in the market at anytime and in the instance of the SSI, this index will account for all the long and short positions on a particular pair in order to determine a bullish or bearish bias. The SSI is then said to work best in a contrarious way when a bias can demonstrated. But why is this the case? Couldn't one expect the majority of traders to be right?