The period of 6–12 months of age is a time of major change in the behaviors and cognitive abilities of human infants. Success on delayed response (DR) has consistently been shown to depend on frontal lobe function by virtually every anatomical, physiological and pharmacological technique in existence. Human adults with more diffuse brain damage have, however, been tested on DR. The human nervous system is not fully mature at birth, and frontal cortex is one of the clearest examples of a structure that matures postnatally. The developmental progression of human infants' performance in DR was almost identical to that for A̅B despite the fact that these two tasks were tested in different laboratories by different testers with infants from different parts of the country. A potential mechanism by which frontal cortex maturation might result in improved Object Retrieval performance is through frontal inhibition of collicular mechanisms.