Karen Hildreth

Rutgers, The State University of New Jersey, Newark, NJ, United States

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Publications (7)14.79 Total impact

  • Karen Hildreth, Debra Hill
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    ABSTRACT: A newly acquired memory is remembered longer when its retrieval is more difficult (i.e., when the time since the last retrieval is longer). In two experiments using an operant conditioning task with 198 infants between 3 and 12 months of age, we presently asked if a reactivated memory also is remembered longer when its retrieval is more difficult. During their first year, infants remember a memory reactivated 1 week after forgetting and the newly acquired memory equally as long. After determining the upper limit (UL) of reactivation at all ages (Experiment 1), we reactivated the memory near the UL and then measured its subsequent persistence (Experiment 2). We found that increasing the training-reactivation interval enhanced retention at 6 months only. These data reveal that increasing retrieval difficulty affects infants' retention of newly acquired and reactivated memories differently. More generally, memory reactivation seems to disproportionately benefit retention in younger infants.
    Developmental Psychobiology 12/2003; 43(3):216-29. · 2.60 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Although reactivation and reinstatement reminders differ procedurally, differences in their memory-preserving effects have been described as artifactual. In three experiments, we examined this conclusion. One hundred and twelve 6-month-olds learned an operant task, forgot it, received a reactivation or reinstatement reminder to recover the inactive memory, and were tested after increasing delays until they forgot it again. In Experiments 1a and 1b, a single reactivation reminder extended infants' memory of an operant mobile task for 2 weeks after reminding, but a single reinstatement extended it for 4 weeks, when testing was discontinued. In Experiment 2, a single reinstatement extended 6-month-olds' memory of an operant train task for 19 weeks after reminding, when infants were almost 1 year old. After reactivation, infants remember this task for only 2 weeks. The finding that the memory-preserving effect of reinstatement is greater by an order of magnitude suggests that procedural differences between the two reminders have functional significance.
    Journal of Experimental Child Psychology 02/2003; 84(1):41-62. · 3.12 Impact Factor
  • Karen Hildreth, Carolyn Rovee-Collier
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    ABSTRACT: A reactivation treatment alleviates forgetting by reexposing organisms to an isolated component of the original event. How long a reactivated memory persists, however, has not been studied systematically. Presently, we documented the retention of a reactivated memory with 6-, 9-, and 12-month-old human infants. All infants learned an operant task, forgot it, and then received a brief reactivation treatment 1 week later. They were tested after increasingly longer delays until the reactivated memory also was forgotten. To provide a picture of retention over the entire first year of life, we combined their data with corresponding data previously obtained from 3- and 6-month-olds in an equivalent task. Although the maximum duration of original retention increases linearly between 3 and 12 months of age, infants consistently forgot the reactivated memory at the same rate as the original one over this period. In essence, a reactivation treatment doubles the life of the memory.
    Developmental Psychobiology 12/2002; 41(3):277-88. · 2.60 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: In two experiments, we examined the effect of repeated reminder treatments on the speed of memory retrieval by 3-month-old human infants. Infants were trained for two consecutive days to kick their feet to produce movement in an overhead mobile. Infants in the one-reminder condition received a 3 min reminder treatment 13 days after the conclusion of training. Infants in the two-reminder condition received one 3 min reminder treatment 6 days after the conclusion of training and a second reminder treatment 7 days later (i.e. 13 days following the conclusion of training). Infants in the no-reminder control condition were not exposed to the reminder prior to the long-term retention test. In the absence of a reminder treatment, infants exhibited complete forgetting during the long-term test. Infants exposed to one reminder exhibited retention when tested 24 h after their only reminder, but not when tested earlier. Infants exposed to two reminder treatments, on the other hand, exhibited retention when tested 1, 4 or 24 h after their second reminder treatment. We conclude that the opportunity to retrieve the memory on a prior occasion facilitated subsequent memory retrieval.
    Developmental Science 12/2001; 3(3):312 - 318. · 3.89 Impact Factor
  • K Hildreth, C Rovee-Collier
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    ABSTRACT: We previously reported that the latency of responding to a memory prime in a reactivation procedure decreases between 3 and 6 months of age. The present study extended this analysis through the first year of life. In this study, 6-, 9-, and 12-month-olds learned an operant task. One week after they had forgotten it, infants were exposed to a component of the original event as a memory prime and were tested after different delays for evidence of retention. Although the interval between the original event and priming increased linearly with age-from 3 weeks at 6 months to 9 weeks at 12 months, the latency of responding after priming decreased linearly with age-from 1 hr at 6 months to 0-1 s at 12 months. The latency of responding after priming was not task-specific; at 6 months, it was identical in two different tasks. These results provide additional evidence that priming in reactivation studies with infants is the same automatic, perceptual identification phenomenon as repetition priming in studies with adults.
    Developmental Psychobiology 01/2000; 35(4):276-89. · 2.60 Impact Factor
  • Infant Behavior & Development - INFANT BEHAV DEVELOP. 01/1998; 21:453-453.
  • Infant Behavior & Development - INFANT BEHAV DEVELOP. 01/1998; 21:460-460.