Contingency is the event that can be possible in the future but cannot be predicted.
So when the US occurs just as often without the tone as it does in the presence of the tone,then no conditioning will accure the tone.This suggests that the animals are sensitive to contingency.
Making the correct adjustments in the money supply can be difficult because each action by the Fed has a lag effect as well as an interactive impact on the variables that the Fed is trying to control..