Canadian-born Albert Holden Abbott and Max Wertheimer were both doctoral students of Oswald Külpe. The symbolic photo was probably taken around the 1st Congress of the Society for Experimental Psychology in Giessen in 1904. Wertheimer wears the Canadian Ahorn leaf on his lapel and has the typical Scottish Glengarry cap on, a sign that Abbott's friend, Henry Jackson Watt could have been the photographer.
Max Wertheimer finished his doctoral thesis in forensic psychology with the title: "Experimentelle Untersuchungen zur Tatbestandsdiagnostik" (Experimental research in the service of the psychological diagnosis of criminal guilt) in 1904, published in 1905.
Already in the summer of 1904, Albert Holden Abbott had written and published his doctoral thesis "Psychologische und erkenntnistheoretische Probleme bei Hobbes" (Psychological and Epistemological Problems in Hobbes) in German, supervised by Oswald Külpe.