Margaret Kennard (1899-1975): not a 'principle' of brain plasticity but a founding mother of developmental neuropsychology

Abstract

According to the 'Kennard Principle', there is a negative linear relation between age at brain injury and functional outcome. Other things being equal, the younger the lesioned organism, the better the outcome. But the 'Kennard Principle' is neither Kennard's nor a principle. In her work, Kennard sought to explain the factors that predicted functional outcome (age, to be sure, but also staging, laterality, location, and number of brain lesions, and outcome domain) and the neural mechanisms that altered the lesioned brain's functionality. This paper discusses Kennard's life and years at Yale (1931-1943); considers the genesis and scope of her work on early-onset brain lesions, which represents an empirical and theoretical foundation for current developmental neuropsychology; offers an historical explanation of why the 'Kennard Principle' emerged in the context of early 1970s work on brain plasticity; shows why uncritical belief in the 'Kennard Principle' continues to shape current research and practice; and reviews the continuing importance of her work.

Figure 1

Headshot of Margaret Kennard extracted from her medical school graduating class photograph (1930). Courtesy of Medical Center Archives of New York-Presbyterian/Weill Cornell.

Figure 2

Photograph of Margaret Kennard with two unidentified colleagues (undated). Courtesy of Cushing/Whitney Medical Historical Library, Yale University.

Figure 3

Kennard’s professional associations during her years at Yale (1931–1943). The nature of the associations is discussed in the text. Figure 3 shows Kennard’s connections with the individuals mentioned, but not their connections with each other, which were considerable: For instance, Fulton had long-term professional relations with Foerster, Brouwer, and Verhaart (Koehler, 2003; 2006) and McCulloch published extensively with Dusser de Barenne. Figure 3 does not include a group of people at Queen’s Square and the London Hospital with whom Kennard obtained clinical neurology training during her Rockefeller Travelling Fellowship.