The specificity of priming effects over the first year of life

Abstract

Despite its significance for the enduring effect of early experience, the specificity of priming on infants' forgotten memories is unknown. This study determined the impact of cue and context changes on the initial priming and retrieval of the reactivated memory over the first postnatal year. Infants were operantly trained with a distinctive cue in a particular context. After forgetting, they were primed and tested for renewed retention with combinations of old and new cues and contexts. Priming was hyperspecific to the original cue and original context at all but 12 months, when the memory was reactivated in a novel context. At 9-12 months, the reactivated memory generalized to a novel cue or context. At younger ages, the reactivated memory generalized only after a very brief prime. These findings indicate that priming in early infancy is initially conservative, buffering against recovering memories in contexts that might no longer be appropriate.

FIGURE 1

(a) A 3-month-old during a reactivation treatment and (b) a long-term retention test (a nonreinforcement phase) in the mobile task. (c) A 9-month-old during a long-term retention test (a nonreinforcement phase) in the train task.

FIGURE 2

Mean baseline ratios of independent groups of 3-, 6-, 9-, and 12-month-olds as a function of test group and task in Experiment 1. Infants were tested with a different cue in the same context or the same cue in a different context 24 hr after a reactivation treatment. Left panel: Groups trained, primed, and tested in the mobile task. Right panel: Groups trained, primed, and tested in the train task. Data for all 3-month-olds and for 6-month-olds in group Test Context Change in the mobile task were from Hayne and Rovee-Collier (1995) and Borovsky and Rovee-Collier (1990), respectively. The data for 6-month-olds in group Test Cue Change in the mobile task and for both groups of 6-month-olds in the train task were from Hartshorn and Rovee-Collier (1997). The dotted line indicates the theoretical baseline ratio of 1.00 (i.e., no retention). The asterisks indicate significant retention (M baseline ratio >1.00). Vertical bars indicate +1SE.

FIGURE 3

Mean baseline ratios of independent groups of 3-, 6-, 9-, and 12-month-olds as a function of test group and task in Experiment 2. Infants were primed with a different cue in the same context or the same cue in a different context and tested 24 hr later with the original cue in the original context. Left panel: Groups trained, primed, and tested in the mobile task. Right panel: Groups trained, primed, and tested in the train task. Data for all 3-month-olds and for all 6-month-olds in the mobile task were from Hayne et al. (1991). The data for 6-month-olds in the train task were from Hartshorn and Rovee-Collier (1997). The dotted line indicates the theoretical baseline ratio of 1.00 (i.e., no retention). The asterisks indicate significant retention (M baseline ratio >1.00). Vertical bars indicate +1SE.

FIGURE 4

Mean baseline ratios of independent groups of infants as a function of age and task in Experiment 3. All infants were given a reactivation treatment with a different cue in the same context and were tested 24 hr later with the different cue in the same context or were given a reactivation treatment with the same cue in a different context and tested 24 hr later with the same cue in the different context. Left panel: Groups trained, primed, and tested in the mobile task. Right panel: Groups trained, primed, and tested in the train task. Data for group React and Test Cue Change at 3 months are from Hayne and Rovee-Collier (1995). The dotted line indicates the theoretical baseline ratio of 1.00 (i.e., no retention). The asterisk indicates significant retention (M baseline ratio >1.00). Vertical bars indicate +1SE.

FIGURE 5

Mean baseline ratios of independent groups of 3- and 6-month-olds as a function of test group and task in Experiment 4. Infants were given a reactivation treatment of the minimum effective duration and were tested 24 hr later with a different cue in the same context or the same cue in a different context. Responding at the baseline level indicates that a group discriminated that either the test cue or the test context was different. If the minimum duration prime were to reactivate only the general features of the original cue or context that were represented in the training memory, then a group would respond significantly above baseline during the 24-hr test (i.e., generalization). Left panel: Groups trained, primed, and tested in the mobile task. Right panel: Groups trained, primed, and tested in the train task. Data for the minimum duration no-change test groups at 3 and 6 months were from Joh et al. (2002) and Sweeney and Rovee-Collier (2002), respectively. The dotted line indicates the theoretical baseline ratio of 1.00 (i.e., no retention). The asterisk indicates significant retention (M baseline ratio >1.00). Vertical bars indicate +1SE.