Which ethologist studied imprinting in greylag geese?

Which ethologist studied imprinting in greylag geese? Konrad Lorenz did. His observations of newly hatched geese became the classic demonstration of filial imprinting.

Lorenz showed that goslings could form a powerful attachment to the first suitable moving object they encountered soon after hatching. In famous demonstrations, incubator-hatched goslings followed Lorenz himself instead of a biological mother because they had encountered him during this early sensitive period. The behavior helped explain how young, nest-leaving birds rapidly learn whom to follow.

Lorenz did not discover every earlier observation related to imprinting: nineteenth-century naturalist Douglas Spalding and Lorenz’s mentor Oskar Heinroth had already contributed important ideas. Lorenz’s work made the phenomenon central to modern ethology and established the importance of timing in early social development. He shared the 1973 Nobel Prize in Physiology or Medicine with Nikolaas Tinbergen and Karl von Frisch. A frequent mix-up is naming Tinbergen, who was also a founder of ethology, but Lorenz is the canonical answer for the greylag-goose imprinting studies.