To understand Douglass's and Brown's attitude to phrenology, we need to recognise that phrenology contained a number of contradictions. Its tendency to attribute fixed characters to nations and races co-existed with an approach which stressed that human capacities and propensities were shaped by the environment. Furthermore, its detailed individual ‘readings’ rarely supported the generalisations it was often tempted to make, and Combe himself saw no conflict between his scientific claims and his commitment to a wide range of social reform causes, including abolitionism.

But it was not just the flexibility of its theory or clinical practice that stopped Douglass and Brown rejecting this ‘peculiar mental science’ outright. Phrenology was far more embedded in their world than we often realise. Indeed, it has been called the psychoanalysis of the nineteenth century, as influential as Freud's theories were in the twentieth. The parallels are quite extensive. Like psychoanalysis, phrenology was initially developed in Vienna by a single individual, but within fifty years had become widely practised in Western Europe and North America. In both cases, they acquired status as a theory or body of knowledge, promulgated by means of lectures and specialist journals and as an effective specialist technique, deployed in private consultations with trained practitioners. But their cultural significance lies in the way they provided a widely adopted idiom used to assess the personality, intelligence and moral worth of strangers and acquaintances. Just as today we easily speak of people ‘projecting’ or ‘overcompensating’ or of having a ‘complex’ of one sort or another, without necessarily subscribing to the metapsychological theories from which such terms derive, so our nineteenth-century counterparts talked of their ‘organ of reference’ or ‘large self-esteem’ without always accepting the craniological hypotheses that they apparently presuppose. Furthermore, phrases of phrenological origin, such as ‘need your head examined’ and ‘low-brow’/‘high-brow’ survive in contemporary speech.

If the medium of psychoanalytical interpretation is listening, then that of phrenology was looking; instead of the talking cure, its method was the examination of heads. As such it was closely associated with physiognomy – the scrutiny of faces. Physiognomy has a much longer history than phrenology, although it remained of merely specialist interest until it was popularised by Johann Kaspar Lavater in his Physiognomische Fragmente (1775–8), which was translated into many languages.