[2] She earned her AB in psychology from the University of the Philippines Diliman, graduating magna cum laude in 1953.

[3] As a social scientist, her activities centered on inequality, health, capacity development, gender, and the environment.

[4] Castillo's 1975 book All in a Grain of Rice concerned rural farmers' responses to changing technology in agriculture.

The book was her most famous and examined the roles of education, income distribution, employment, and migration in rural areas.

[4] Castillo served on the governing board of the International Development Research Centre of Canada from 1979 to 1990.

[3] She chaired the board of the International Potato Center[5] and was a trustee of the Philippine Institute for Development Studies.