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PubMed1995

Syntactic cues in the acquisition of collective nouns.

One basic finding in the study of word learning is that children tend to construe a word describing an object as referring to the kind of whole object, rather than to a part of the object, one of its properties, or the substance it is made of. This has been taken as evidence that there exist certain special constraints on word meaning that guide children to favor the kind-of-object interpretation when exposed to a new word. There are descriptive problems with this proposal, however, as it cannot explain how children learn other kinds of words, such as names for specific people, substances, parts, events, collections, and periods of time. These problems motivate an alternative theory in which young children possess several distinct conceptual categories--including "individual", which is more abstract than "whole object"--and can use syntactic cues to determine the conceptual category that a new word belongs to. This theory is explored in two experiments in which we attempt to use syntactic cues to teach children and adults novel collective nouns--words that refer to groups of objects. The results indicate that children can use such cues to learn names for kinds of individuals that are not whole objects, although they are less able to do so than adults. Candidate explanations for why this developmental difference exists are discussed and implications are drawn for theories of word learning and conceptual representation.

Adult↗
PubMed1982

Increased naloxone reversibility in fentanyl dose-dose discrimination.

Two groups of rats were trained to discriminate 0.04 mg/kg of fentanyl from saline (drug-saline discrimination) or from 0.02 mg/kg of fentanyl (dose-dose discrimination). The ED50 of naloxone for antagonizing the discriminative effects of 0.04 mg/kg fentanyl was 0.05 and 0.0062 mg/kg, respectively. This 8.1 fold difference in naloxone reversibility suggests that dose-dose discrimination yields higher pharmacological specificity than the commonly used drug-saline discrimination.

Animals↗
PubMed1982

OR discrimination: a new drug discrimination method.

Rats were trained to respond on one of two levers for food (drug lever) after injections of either 0.04 mg/kg fentanyl or 10 mg/kg cocaine HCl, and to respond on the saline lever after saline injections. The acquisition data indicate that this OR discrimination is feasable in the rat, though it developed slowly due to a bias of responding on the drug lever. The generalization data obtained here suggest that the OR discrimination method may establish relations between the cuing properties of drugs which are not apparent with the commonly used drug-saline method of drug discrimination.

Animals↗
PubMed1991

Effect of fatty acids on the proliferation of concanavalin A-stimulated rat lymph node lymphocytes.

1. The effect of a range of fatty acids upon concanavalin A-stimulated [3H]thymidine incorporation into rat lymphocytes was investigated. 2. All fatty acids tested inhibited the response to mitogen but the extent of the inhibition was dependent upon the fatty acid concentration used, the time of addition of fatty acid and the duration of exposure of the cells to fatty acid. 3. All fatty acids were inhibitory at concentrations of 50 microM or above; at lower concentrations some were inhibitory and some were stimulatory. Above 50 microM the inhibitory effect was concentration dependent; the greater the fatty acid concentration, the greater the inhibition. 4. The longer the lymphocytes were exposed to the fatty acid the greater was the inhibitory effect. This was true if the fatty acids were added at the same time as the mitogenic stimulus or if they were added before or after the stimulus. Some fatty acids maintained their inhibitory effect when added 24 or 48 hr after the mitogenic stimulus. 5. Generally unsaturated fatty acids were more inhibitory than saturated fatty acids; the greatest inhibition of proliferation was caused by eicosapentaenoate and arachidonate and the least inhibition by myristate and palmitate. 6. Inhibition was greater in the absence of serum. 7. Inhibition by unsaturated fatty acids could be partially or totally relieved by addition in combination with myristate or palmitate, suggesting that the inhibitory effect of fatty acids may be due to alteration of membrane fluidity caused by an imbalance of fatty acids presented to the cells. 8. PGE2 levels were similar in the medium of cells grown in the presence of fatty acids with varying inhibitory effects, indicating that PGE2 production is not the sole mechanism of suppression of the proliferative response. 9. Although the mechanism by which fatty acids exert their effect remains to be determined, these results indicate that lymphocyte proliferation and so an immune response could be influenced by dietary lipid manipulation.

Animals↗
PubMed1987

A test of color constancy in 4-month-old human infants.

Forty-five 4-month-old infants were tested for color constancy using a familiarization, paired-comparison paradigm. Infants were familiarized and tested with colored stimuli under two conditions: (1) no change in the illuminant between familiarization and test and (2) a change in the illuminant between familiarization and test. Infants correctly recognized the familiarization color when tested with no change in the illuminant. Infants tested with a change in the illuminant correctly recognized the familiar color under some conditions yet failed to do so under others. Several explanations are considered for these results and it is concluded that color constancy operates immaturely at 4 months of age.

Attention↗
PubMed1991

Generalized oddity performance in preschool children: a bimodal training procedure.

Oddity performance requires relational discriminative responding, which typically is difficult to establish in children with MAs below five. In Experiment 1, a combination intrasubject reversal and multiple baseline across subjects design was used to establish the internal validity of a bimodal intervention in establishing generalized oddity performance. Six of seven children demonstrated oddity responding when presented with stimuli that instantiated the oddity relation in the visual and auditory modalities simultaneously. Oddity performance was evaluated with both reversal assessments and assessments with new sets of stimuli. The newly acquired oddity performance was durable; the six children continued to respond discriminatively when returned to a visual-only task on which they previously had been unsuccessful. Utilizing a reversal assessment more stringent than that of Experiment 1, Experiment 2 replicated this effect. The present studies are the first to demonstrate the utility of bimodal training in establishing oddity performance. The bimodal procedure is discussed with respect to the theoretical positions of Gibson, Dinsmoor, and Dixon.

Attention↗
PubMed1982

Hallucinogens as discriminative stimuli: a comparison of 4-OMe DMT and 5-OMe DMT with their methythio counterparts.

Rats, trained to discriminate 1.5 mg/kg of the hallucinogenic agent 5-methoxy-N,N-dimethyltryptamine (5-OMe DMT) from saline in a two-lever drug discrimination task, were challenged with various doses of the 4-methoxy, 4-methylthio and 5-methylthio derivatives of DMT. The 5-OMe DMT cue was found to generalize to all three of these agents; the order of potency is 5-OMe greater than 5-SMe greater than 4-OMe greater than 4-SMe DMT.

Animals↗