I have long held a deep affection for the phenomenon of proactive inhibition. It has not always returned this affection. At times it has behaved in quite unexpected 'ways and has see~ed particularly reluctant to accept my theoretical gifts. In view of these experiences with proactive inhibition, I suppose that I should have been prepared for the series of events that I will relate in this and the following chapter. I was not prepared for them, and I am convinced they would never have happened except for one of those casual or incidental decisions that are inevitably necessary in designing experiments. This decision will become exposed in due time. It is necessary fIrst to give the background for a major experiment we undertook in the fall of 1971.