Eric S.E. Cogan matriculated at the Boys' High School, Grahamstown, in 1909. Continuing his studies at Rhodes University College, Grahamstown, he was awarded the BA degree by the University of the Cape of Good Hope in 1912. With the aid of an entomological scholarship he continued his studies at Ohio State University in the United States, where he qualified as Master of Arts (MA) and Doctor of Philosophy (PhD). His doctoral studies dealt with the suborder Homoptera, an extremely varied group of terrestrial plant feeders, many of which are serious pests of cultivated plants. His work led to three papers in the Ohio Journal of Science: "A preliminary list of the Jassoidea of Missouri with notes on species" (1915, as co-author of Edmund H. Gibson), "Homopterous studies. Part 1: Contribution towards our knowledge of the Homoptera of South Africa" (1916), and "Homopterous studies. Part 2: Morphological studies of the superfamily Jassoidea" (1916). Also in 1916 he submitted his doctoral dissertation, Studies of the homopterous families Cercopidae and Jassoidea with special reference to the South African fauna. The dissertation was published in the series Ohio State University: Contributions from the Department of Zoology and Entomology, No. 46, 1916.
Cogan returned to South Africa in 1916 and the next year became a foundation member of the South African Biological Society. He was still a member in 1919, but no longer in 1920. For some time he worked as lecturer in entomology at the Cedara School of Agriculture in Natal. Around 1918 he was appointed to teach entomology at the University of Stellenbosch, where he remained for about two years. He became a member of the South African Association for the Advancement of Science in 1917 and at the association's meeting in Stellenbosch that year read two papers: "Some phases of applied entomology in South Africa" and "Entomological education in the United States". Both papers were published in the association's Report for that year.