This paper reports on the effect of iron supplementation on neural indices of habituation using auditory event-related brain potentials within a three-arm, double-blind, double-dummy, individual randomized trial in Bangladesh, in which 3,300 eight-month-old children were randomly selected to receive three months of daily iron syrup (12.5 mg iron), multiple micronutrient powders (including 12.5 mg iron), or placebo.