It was found desirable after a problem had been solved to present a new and radically different series of settings in order to determine to what extent the subject had learned to choose the correct door by memorizing each particular setting. These supplementary observations may be known as control experiments, and the settings as supplementary settings. In case of these, as for the original settings, the essential facts are presented in tabular arrangement. Settings for Control Experiments PROBLEM 1. First at left end Doors No. of No. of Settings open doors open right door 1..................2.3.4......................3..................2 2..................6.7.8.9....................4..................6 3..................3.4.5......................3..................3 4..................4.5.6.7.8.9................6..................4 5..................6.7.8.9....................4..................6 6..................1.2.3.4.5..................5..................1 7..................2.3.4.5.6.7.8..............7..................2 8..................3.4.5.6.7.8................6..................3 9..................5.6.7......................3..................5 10..................1.2.3.4.5.6.7.8.9..........9..................1 PROBLEM 2. Second from right end Doors No. of No. of Settings open doors open right door 1..................5.6.7.8....................4..................7 2..................2.3.4.5.6..................5..................5 3..................1.2.3.4.5.6.7.8.9..........9..................8 4..................5.6.7......................3..................6 5..................1.2.3.4....................4..................3 6..................4.5.6......................3..................5 7..................2.3.4.5....................4..................4 8..................1.2.3......................3..................2 9..................1.2.3.4.5.6.7..............7..................6 10..................2.3.4.5.6.7.8.9............8..................8 PROBLEM 3. Alternate left and right ends