The effect of multiple reminders on long‐term retention in human infants

Abstract

The present series of experiments compared the effects of single- and multiple-reminder procedures on the long-term memory of 3-month-old human infants. Subjects were trained in the mobile conjugate reinforcement paradigm, and the reminder treatment was a brief, noncontingent exposure to the moving mobile. In Experiment 1, independent groups received one or two reminder treatments during the 3 weeks following the conclusion of training. Independent groups were tested 1, 3, 7, 14, or 22 days following the last (or only) reminder (i.e., 21-42 days after the end of training). Although retention was equivalent 1 day after one or two reminder treatments, subsequent retention was significantly prolonged by the second reminder treatment: infants receiving a single reminder treatment demonstrated no evidence of retention 7 days after the reminder, but infants receiving two reminder treatments demonstrated perfect retention as long as 14 days later. In Experiment 2, retention was observed 14 days after two reminder treatments irrespective of whether the treatments were presented during the first and second or the third and fourth weeks following the conclusion of training. In Experiment 3, the effect of three reminder treatments on retention was examined. Although retention was excellent when infants were tested 1 day after the third reminder, retention after longer intervals was no better than that observed after a single reminder treatment.

Minimum duration of reactivation at 3 months of age

“…Group 120 s/Day 20 had a mean baseline ratio not signi®cantly above 1.00, t(5)`1, and a mean retention ratio signi®cantly below 1.00, t(5) 3.27, p`.01. By comparison, Group 180 s/Day 20 (Hayne, 1990) had a mean baseline ratio that was signi®cantly above 1.00 and a mean retention ratio that was not signi®cantly less than 1.00 (Table 2).…”

“…Delays longer than 3 weeks after training were not used in Experiment 2 because previous studies have shown that a 3-min (180-s) reactivation treatment also recovers the forgotten memory after 4 weeks (Hayne, 1990;Hayne & Findlay, 1995;Rovee-Collier et al, 1980), which is the upper limit of reactivation at this age (Greco, Rovee-Collier, Hayne, Griesler, & Earley, 1986;Hartshorn, Wilk, Muller, & Rovee-Collier, 1998).…”

“…At 3 months of age, a forgotten memory can be reactivated 6 days (Hayne, 1990), 13 days (Rovee- Collier et al, 1980), 20 days (Hayne, 1990), or 27 days (Rovee-Collier et al, 1980) after training if infants are exposed to a 3-min reminder. Experiment 1 determined that 120 s is the minimum duration of exposure to a reminder that is necessary to reactivate 3-month-olds' memory 1 week after forgetting.…”

“…To answer these questions, we gave independent groups of 3-month-olds a brief reactivation treatment after different delays since the memory was forgotten (recall that infants of this age exhibit retention 5 but not 6 days after training) and tested them for evidence of renewed retention 1 day later. If a 120-s exposure was not effective, then we did not plan to test any additional groups because a 180-s exposure is effective in reactivating a forgotten memory 20 and 27 days after training at 3 months (Hayne, 1990;RoveeCollier et al, 1980).…”

“…In studies with 3-month-olds, infants recognize their training mobile for 5 but not 6 days (Butler & Rovee-Collier, 1989;Hayne, 1990). Their training memory also can be reactivated by exposure to the original training mobile (Rovee-Collier, Sullivan, Enright, Lucas, & Fagen, 1980).…”