What’s Your Type? takes us back to 20th-century attempts at personality definition. The Myers-Briggs Type Indicator (MBTI) was used extensively for this purpose, mainly by corporations seeking to recruit staff of the most suitable calibre. Its progenitor was Katharine Cook, born in 1875 in Michigan. She was unprepossessing as a child, with thick glasses and tangled hair. When she went to Michigan Agricultural College, she met Lyman Briggs, a farm boy with a similar background to her own. Both were bright, self-reflective and forward-looking. After they married, Katharine, who was determined to bring up their children effectively, devised a programme to this end, calling it her ‘cosmic laboratory of baby training’. Unfortunately, two sons died in infancy, so the focus shifted entirely on to her daughter, Isabel. Born in 1897, Isabel was bright and eager like her mother, and spoke in full sentences by the age of two. She married in 1918, becoming Isabel Briggs Myers. She and her mother were strongly attached to one another and became lifelong collaborators.

In 1923, in her late forties, Katharine read Carl Jung’s newly published Psychological Types. This proved transformational for her. In his book, Jung introduced his theory that everyone conformed to a psychological type, being either extrovert or introvert. In addition, Jung claimed, all individuals demonstrated a preference for