Hey there pooks - the person that is out in front cannot tell if they are drafting unless they look behind them. There is no "drag" effect, if that is what you are asking.

It is very easy to drop someone when you are on the front - particularly if they are a slower rider, or are tired. Hence glancing back every now and again, and checking if you are doing the right speed for them.

In a race situation, you tend to work together at the same speed but in a training ride, you should be riding at the speed of the slowest people.