A conditioning analysis of infant long-term memory.

The long-term retention of conditioned operant footkicks by 3-month-old infants was assessed in 2 studies. In both, infants were trained in a conjugate reinforcement paradigm in which footkicks produced conjugate activation of the components of an overhead crib mobile. After 2 training sessions, retention (cued recall, savings) was assessed cross-sectionally in a third session scheduled after varying intervals. In experiment 1, 32 infants were tested after intervals of 48, 72, 96, or 120 hours; in experiment 2, 24 infants were tested after 96, 144, 192, or 336 hours. No evidence of forgetting was observed for as long as 192 hours following original training. Although both retention measures indicated a significant memory deficit in the group tested after 336 hours (2 weeks), some individuals continued to exhibit substantial recall and savings after this retention interval. A conditioning analysis was viewed as a logical means by which to bridge the gap between animal and adult human models of memory.