Gunster introduced the word 'flip thinking' to describe the process of transforming 'yes-but' to 'yes-and' behaviour.
Gunster and his team have conducted Yes-but® programs for more than 500 organisations, including national and international top 100 companies like Shell, Philips, Accenture, ABN AMRO, Unilever, Nike and Telfort. During the years more than 500.000 people in The Netherlands followed one or more of his programs.
Gunster is best selling author of several books on ‘flip thinking’. His first, "Ja-maar wat als alles lukt" immediately became a bestseller in the Netherlands and was translated into English in 2007 ("Yes-but what if it all works out?").
Besides the training programs Berthold Gunster developed a series of Yes-but® products, for example the Yes-but® Poster and the Yes-but® Quandary Cards.