Walter's talk for the Second Geoffrey Parr Memorial Lecture, 8 October 1966. Here, Walter describes his early collaboration with Parr at the Maida Vale Hospital; the Lewes Gaol Case in 1938; his experiences in the Second World War; the discovery of delta waves; the use of stroboscopes in epilepsy research; the role of amateurs in scientific research; the physiological effects of the experimenter/subject relationship; the discovery of contingent negative variation (CNV) and its possible applications; and problems with a statistical approach.