Immediate and long-term memory for reinforcement context: the development of learned expectancies in early infancy

Infants were pretrained to move crib mobiles containing 6 or 10 identical objects by means of footkicking and were then exposed to a reinforcer containing only 2 objects. Relative to infants with no prior history of reinformcement with either of the "larger mobiles, infants shifted to the "smaller" mobile had higher kick rates, and, in addition, their visual attention decreased and negative vocalizations increased. These effects were not transient but persisted 24 hours later in infants experiencing the larger (10- to 2-object) shift. The results suggested that infants develop reward-expectation habits which continue to influence behavior for periods of at least 24 hours.