Extended conditioning and 24-hour retention in infants.

The successive contribution of brief daily conditioning sessions to the relatively long-term retention of stimulus-response interaction was assessed in 30 3-month-old infants. On each of 3 days, infants received a characteristic acquisition and extinction period, preceded by a 24-hr retention test. In addition to kick rate, duration of attention to a visual conjugate reinforcer (mobile) was measured. On the fourth day, the specificity of original learning was explored by exposing half the infants to a novel reinforcing agent while the remaining infants continued to view the original training mobile. Both kicks and attention significantly increased across successive retention tests for the first 3 days; on Day 4, infants viewing the novel mobile kicked significantly less and attended significantly longer than infants viewing the familiar mobile. Subsequent reattainment of high kick levels by the experimental group on Day 4 appeared to be highly individualistic and, in many instances, discontinuous.