Dijkstra went on a trip to California, visiting universities and research centers. While doing so, he got annoyed by the many researchers who viewed the difficulties underlying multi-person software projects as "communication problems" and who, therefore, advocated new specification languages.
On the basis of an IFIP WG 2.3 meeting in Han-sur-Lesse (Belgium), Dijkstra expressed his misgivings about the overhead projector. He preferred the blackboard much more and the interaction it required between him and the audience. That is, he preferred to give "lectures", not "presentations". Instead of preparing everything in advance, he wanted room to improvise during his lectures.