Things can get out of control quickly when a horse uses the reacting side of its brain, and it's really no different with pilots. There are a number of examples of the bad things that happen when pilots react rather than think. If the pilot of a multiengine airplane reacts without thinking when an engine fails, he would have been better off at the controls of a single. Too frequently, pilots have mistakenly feathered the one engine that was still cooperating. As a result, multi-engine students are taught the phrase, "Dead leg, dead engine," to help them think about what's happening so they can correctly identify which engine has failed before they do something precipitous. Even then, they're taught not to rush to judgment, but to confirm that they have, in fact, selected the correct engine before attempting to feather it. If when they pull back the throttle the engine noise changes or the airplane yaws toward the engine they pulled, they've made the wrong choice and they're about to kill the engine that's been pulling extra duty while its stable mate was loafing. It's only after they've thought through the situation (with the thinking side of their brain) and made sure they've identified the malingering engine that they should go ahead and feather it.