Biomedical subjects

P Gerhardstein

Publications and source records attributed to P Gerhardstein.

6 recordsLinked to original sources

PubMed2000

A dissociation in infants' memory for stimulus size: evidence for the early development of multiple memory systems.

Adults' memory performance on recognition (explicit memory) tests is sensitive to stimulus size, but their performance on priming (implicit memory) tests is not. This memory dissociation is taken as evidence for two, functionally distinct memory systems. Young infants, however, are thought to possess only a single representational system that supports implicit memory; the system that supports explicit memory is thought not to mature before 8-9 months of age. In two experiments with 54 infants, we asked if 3-month-olds exhibit a memory dissociation for stimulus size on recognition and priming tests. All infants learned to move a mobile displaying +s of a given size. In Experiment 1, infants recognized +s in the original size but not 33% smaller or larger. In Experiment 2, +s were effective memory primes in a reactivation task, irrespective of size. The finding that young infants exhibit a memory dissociation for stimulus size adds to growing evidence that two memory systems are functional from early in development.

Association Learning↗

PubMed1998

Developmental changes in the specificity of memory over the first year of life.

In two experiments with 260 infants between 2 and 12 months of age, we examined how differences between the conditions of encoding and retrieval affect retention. Initially, 9- and 12-month-olds were tested with a different cue (Experiment 1) or in a different context (Experiment 2) after delays spanning their respective forgetting functions. These data were then combined with corresponding data previously collected from 2-to 6-month-olds trained and tested in an equivalent task. The resulting analyses revealed that the specificity constraints on memory retrieval become progressively looser at the extremes of the forgetting function with age. With increasing age, retention was less affected by cue changes after shorter absolute delays and, except at 6 months, by context changes after longer absolute delays. This pattern dovetails with evidence of decreasing specificity in the retrieval cues required for deferred imitation during infants' 2nd year and reveals that the memory abilities of older children evolve gradually from early in infancy.

Age Factors↗

PubMed1998

Perceptual constraints on infant memory retrieval.

In three experiments with 78 3-month-olds, we asked what determines whether or not a stimulus will pop out and cue retrieval from long-term memory. All infants were trained with mobiles displaying either Qs (feature-present stimuli) or Os (feature-absent stimuli) and were tested 24 h later. When the diagonal line of the Q bisected its rim, feature-absent stimuli controlled retrieval in tests with homogeneous displays, and stimulus novelty controlled retrieval in tests with pop-out displays. A follow-up experiment revealed that the similarity between Q and O determined whether or not Q popped out: When its tail projected externally from the rim, Q popped out and cued retrieval, but O did not (search asymmetry). When its tail projected internally from the rim, however, 3-month-olds failed to discriminate Q from O (the externality effect). These data reveal that target-distractor similarity constrains whether or not a feature-present stimulus will pop out and cue retrieval.

Association Learning↗

PubMed1998

Age-related hemispheric asymmetry in object discrimination.

Young and elderly observers judged whether two sequentially presented images in either the left or right visual field (LVF or RVF) were the same or different. The two objects depicted were always from the same entry-level category, but could differ only in viewpoint (a "same" trial--observers were instructed to ignore viewpoint changes) and/or in exemplar (a "different" trial). Young observers showed no difference in sensitivity across visual fields. Elderly observers were less sensitive overall than young observers, and were less sensitive to stimuli presented in the LVF-RH than in the RVF-LH. The results of this experiment support the hypothesis that one type of visual cognitive functioning declines with age faster in the right hemisphere than in the left hemisphere.

Adolescent↗

PubMed1998

The ontogeny of long-term memory over the first year-and-a-half of life.

This research documents the development of long-term memory in human infants from 2 months through the end of the first year-and-a-half of life. In the initial study phase, we trained 6- to 18-month-old human infants in an operant task and tested them after increasing delays until they exhibited no retention for 2 successive weeks. In the second phase, their data were combined with data previously obtained from 2- to 6-month-olds in an equivalent task. The resulting function revealed that the duration of retention increases monotonically between 2 and 18 months of age. This increase was not due to age differences in original learning. This is the first systematic analysis of the course of long-term memory across an extended period of infant development that is based on standardized parameters of training and testing. It provides a reference function against which measures of retention from infants of different ages that are obtained in different memory tasks with different parameters can be meaningfully compared.

Age Factors↗

PubMed1998

Levels-of-processing effects in infant memory?

In 3 experiments, we manipulated 3-month-olds' attention to different components of a training display and assessed the effect on retention of those components. Attention was manipulated via a pop-out display (one target amidst 6 distractors) that enhances selective attention to the target relative to the distractors, and retention was assessed with displays composed entirely of targets or distractors. In Experiment 1, infants recognized both target and distractors after 1 day, confirming that both are initially encoded at some level. In Experiment 2, infants recognized a target L and distractor Ls after delays longer and shorter, respectively, than infants trained with Ls in a homogeneous display. Experiment 3 replicated the preceding pattern of results with a + stimulus. Thus, increasing or decreasing attention to an item during encoding produces a corresponding increase or decrease in its memorability. This finding is consistent with a levels of processing account and is inconsistent with accounts that deny a capacity for explicit memory to prelinguistic infants.

Association Learning↗