 The research team also modified the experimental design after the results of "Casey", these indicated that crews were able to learn rapidly and were able to accommodate the level of difficulty, within a few sessions, to an effective level.Beginning with "Cowboy", the air-defense crews were presented with a series of sessions each of which had a higher task load than the previous session.The task load was made up of two variables, kind and number of hostile aircraft and characteristics of friendly traffic (among which the hostile aircraft were sprinkled).