The influence of negative affect on the retrieval of information from memory during infancy was investigated in two studies through the use of an operant conditioning paradigm. The procedure used, known as "mobile conjugate reinforcement," involves a free operant task in which an infant is reinforced for footkicking by the movement of an overhead crib mobile. This procedure produces rapid learning in 2- to 4-month-old infants: the infant learns the footkick response in a distinctive setting in which details of the crib, stands, mobile, and even ribbon serve as possible contextual cues for the production of the conditioned response when the infant is returned to that specific context at a later time. Results of the first experiment indicated that infants' crying in reaction to a change in the number of mobile objects displayed (i.e., reward shift) had a deleterious effect on their memory for a learning task, thus providing some of the first direct evidence that negative affect influences infants' memorial capabilities. The second experiment was conducted to investigate two possible explanations for the findings: state-dependent retention and memory loss. Results refuted the state-dependent hypothesis. Generally, results provided evidence that negative affect associated with an event produces rapid forgetting of that event, but that this forgetting is not a permanent loss of information. Such forgetting may best be viewed as the result of retrieval failure. (RH)