Infants' memory processing of a serial list: List length effects

Six-month-olds, trained with a three-mobile serial list, exhibit a primacy effect 24 h later. In three experiments, we demonstrated that increasing li st length impairs their memory for serial order. In all experiments, 6-mont h-olds were trained with a five-mobile list. In Experiment I, infants faile d to exhibit a primacy effect on a 24-h delayed recognition test, recognizi ng mobiles from all serial positions. In Experiment 2, infants did exhibit a primacy effect on a reactivation (priming) test, suggesting that they may originally have encoded serial-order information. Experiment 3 confirmed t hat serial-order information was represented in infants' training memory. A fter the reactivation treatment, infants were precued with one list member and tested for recognition of another. When precues specified valid order i nformation, infants recognized test mobiles from the later serial positions . The memory dissociation for serial order on delayed recognition and react ivation tests adds to the growing evidence that young infants possess two f unctionally distinct memory systems. (C) 1999 Academic Press.