In 1910 he was awarded a London University DSc for his thesis “The Use of the Theory of Correlation in Psychology” which applied statistical methods devised by Karl Pearson; the thesis provided the nucleus for his book The Essentials of Mental Measurement.
Brown undertook medical training at King's College London and graduated MBBCh in Oxford in 1914.
In WW1 he served in the Royal Army Medical Corps, working as a neurologist with shell shock victims, initially in France and then as commandant of the Craiglockhart Hospital for Neurasthenic Officers.
He returned to his post of Reader in psychology at King's College London meanwhile continuing to acquire medical qualifications: he earned a DM in 1918, MRCP in 1921 and was elected FRCP in 1930.
[2] In 1921 Brown succeeded his teacher William McDougall as Wilde reader in mental philosophy.