This is the second of the two lectures that Nikolaas Tinbergen held in Lindau. Tinbergen pioneered experimental investigations on top of the “watching and wondering” which characterized most of ethology during the first half of the 20th century. But both lectures concern what can be learnt concerning autism by applying the methods of ethology, i.e. watching animal behaviour. In his first lecture at the Lindau Meeting 1978, he described the research project that he and his wife Elisabeth had started around 1970 and which was reported on already in his Nobel Lecture in Stockholm 1973. The main conclusion was that autism is not connected with the genes or is an effect of a brain damage. Instead a more psychoanalytical hypothesis was put forward, that autism derives from a hyperanxiety developed in the child through early loss of contact with the mother. In his second lecture, the present one, Tinbergen reported that they now had found a cure for autism. This cure originated with an American psychiatrist, Martha Welch, who had pioneered a therapy where the mother holds the autistic child for extended periods of time and thereby establishes contact with it. Tinbergen refers to an investigation where he and his wife found that almost all autistic children responded to the cure. Inspired by this result, they wrote a book together entitled “Autistic Children: New Hope for a Cure”, published in 1983. As of today, a detailed understanding of autism is still missing, but it seems clear that the hypothesis of the two Tinbergens is not the whole story and that there may be some genetical aspects of autism. Concerning their optimism of having found a cure, this seems also to have been somewhat premature.