ABSTRACT
Thirty-seven 3-year-old children, who had learned a 9-action event sequence ("making Play-Doh spaghetti") when they were 20 months old, returned to the lab to determine whether they would be able to verbally and/or behaviourally recall the event after a 12- to 22-month delay. Children originally participated in the event either one or three times and experienced different parts of the event either at three distinct locations (spatial condition) or at a single location (nonspatial condition). Results show very little evidence of long-term memory for the event after one to two years. Returning children did not verbally recall the event, and they did not perform more actions or sequence the event more accurately than controls, with the exception of the older experimental children who had a tendency to sequence the event more accurately than same-aged controls. Although the results indicate that young children's memory for novel events is not very enduring, there were individual differences in children's ability to remember the event. These differences are discussed in terms of potential differences in cognitive abilities and changing knowledge about retrieval strategies or memory.
Subject(s)
Child Development , Mental Recall , Analysis of Variance , Child, Preschool , Choice Behavior , Cues , Follow-Up Studies , Humans , Nonverbal Communication , Play and Playthings , Practice, Psychological , Psychological Theory , Retention, Psychology , Time Factors , Verbal BehaviorABSTRACT
The role of knowledge in children's inferences was investigated in 3 experiments. Experiment 1 examined developmental changes in the role of categorical membership, perceptual appearance, and item complexity in inferences for natural kind and artifact concepts. Preschoolers (5-year-olds), second graders (8-year-olds), and fourth graders (10-year-olds) were taught novel properties about target concepts and asked whether each of 4 probes had those properties. Probes varied in category membership and perceptual appearance relative to the target item. Item complexity also varied. Experiments 2 and 3 examined inferences with known and unknown concepts for familiar and unfamiliar properties. Older children's knowledge led to differential weighting of categorical information over appearance but only for known concepts and/or familiar properties. Preschoolers made no distinction between category and appearance for either known or unknown concepts. Additionally, as target item complexity increased, older children made more inferences than preschoolers. No differences between inferences about natural kind and artifact concepts were found. The role of theories and knowledge in children's drawing of inferences is discussed.
Subject(s)
Concept Formation , Generalization, Psychological , Mental Recall , Problem Solving , Attention , Child , Child, Preschool , Discrimination Learning , Female , Humans , Male , Pattern Recognition, VisualABSTRACT
Gastrin releasing peptide (GRP) is a peptide hormone containing 27 amino acids which is structurally analogous to the amphibian peptide bombesin. GRP serves a variety of physiological functions and has been implicated in the pathophysiology of small cell lung cancer. Previous work has demonstrated that the modified C terminus of GRP, N-acetyl-GRP-20-27, exerts full agonist activity in a variety of assay systems. However, no systematic comparison of binding of GRP fragments to its receptor and mitogenic potency has been reported. To investigate whether smaller GRP fragments could bind to the GRP receptor without stimulating mitogenesis, we performed binding inhibition and thymidine uptake assays with Swiss 3T3 fibroblasts. These studies were facilitated by the development of a novel tritiated GRP-based radioligand, [3H-Phe15] GRP-15-27, which exhibits enhanced chemical stability compared to iodinated GRP derivatives. We examined a series of C-terminal GRP fragments, from the pentapeptide to the octapeptide, with both N-acetyl and free amine moieties at the N terminus. N-Acetylated derivatives were more potent than their primary amine counterparts in both assays. Deletion of N-terminal residues from GRP-20-27 resulted in significant loss of potency in both assays: the EC50 values of N-acetyl-GRP-21-27 were 10(2)-fold higher than N-acetyl-GRP-20-27, those of N-acetyl-GRP-22-27 were 10(4)-fold higher, and N-acetyl-GRP-23-27 showed minimal activity at concentrations below 100 microM. These results suggest that 1) both His20 and Trp21 play an important role in binding of GRP to the receptor, and 2) for this series of N-terminal deletions, binding to the receptor and mitogenic activity are tightly coupled.
