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D A Baldwin

Publications and source records attributed to D A Baldwin.

At least 19 recordsLinked to original sources
PubMed2000

Further evidence of associations of type a personality scores and driving-related attitudes and behaviors.

The present study examined the effects of Type A personality on specific self-reported driving attitudes and behaviors when operating a motor vehicle. 102 undergraduate students completed the student version of the Jenkins Activity Survey (Form T) and several questionnaires asking participants about their driving history, driving attitudes, and driving behaviors. When the full range of Type A scores were examined, Type A personality was significantly related to more traffic accidents, greater frequency of breaking traffic laws, higher impatience when driving, more displays of aggression on the road, and engaging in more risky driving behaviors (rs<.17). When extreme Type A and Type B scores were compared, Type A drivers reported being involved in significantly more motor vehicle accidents and reported displaying more aggression on the road. Further research should examine actual behavioral data using more diverse samples to validate the results.

Adolescent↗
PubMed1997

Do children with autism use the speaker's direction of gaze strategy to crack the code of language?

Normal toddlers infer the referent of a novel word by consulting the speaker's direction of gaze. That is, they use the Speaker's Direction of Gaze (SDG) strategy. This is a far more powerful strategy than the alternative, the Listener's Direction of Gaze (LDG) strategy. In Study 1 we tested if children with autism, who have well-documented impairments in joint attention, used the SDG or the LDG strategy to learn a novel word for a novel object. Results showed that although 70.6% of children with mental handicap passed the test by making the correct mapping between a novel word and a novel object, via the SDG strategy, only 29.4% of children with autism did so. Instead, their reliance on the LDG strategy led to mapping errors. In Study 2 a group of normal children, whose chronological age (24 months old) was equated with the verbal mental age of the 2 clinical groups in Study 1, was tested using a similar procedure. Results showed that 79% of this normal group passed the test by making the correct mapping between a novel word and a novel object using the SDG strategy. Taken together, the results from both studies suggest that children with autism are relatively insensitive to a speaker's gaze direction as an index of the speaker's intention to refer. This result is consistent with previous findings showing that children with autism are relatively "blind" to the mentalistic significance of the eyes. Discussion centers on how the absence of an SDG strategy might disrupt specific aspects of language development in autism.

Attention↗
PubMed1996

Isolation and characterization of cDNAs encoding transcription factor IIB from Arabidopsis and soybean.

Clones containing the complete coding regions for transcription factor IIB (TFIIB) were isolated from cDNA libraries of Arabidopsis and soybean. The predicted protein sequences for TFIIB from these two species are highly homologous and contain the same structural motifs and organization as seen in other eukaryotes and Archaebacteria. Southern and Northern blots and primer extension for Arabidopsis TFIIB indicate a low copy number gene encodes a transcript of 1400 nt with a leader of 180 nt. Phylogeny analysis places the plant proteins into one group nearly equidistant from metazoans, fungi, and Archaebacteria.

Amino Acid Sequence↗
PubMed1996

Infants' reliance on a social criterion for establishing word-object relations.

The language children hear presents them with a multitude of co-occurrences between words and things in the world, and they must repeatedly determine which among these manifold co-occurrences is relevant. Social factors--such as cues regarding the speaker's referential intent--might serve as one guide to whether word-object covariation should be registered. In 2 studies, infants (15-20 months and 18-20 months in Studies 1 and 2, respectively) heard novel labels at a time when they were investigating a single novel object; in one case the label was uttered by a speaker seated within the infant's view and displaying concurrent attention to the novel toy (coupled condition), whereas in the other case the label emanated from a speaker seated out of the infant's view (decoupled condition). In both studies, subsequent comprehension questions indicated that infants of 18-20 months registered a stable link between label and object in the coupled conditions, but not in the decoupled condition, despite the fact that covariation between label and object was equivalent in the 2 conditions. Thus, by 18-20 months children are inclined to establish a mapping between word and object only when a speaker displays signs of referring to that object.

Age Factors↗
PubMed1993

Infants' ability to consult the speaker for clues to word reference.

This research examines whether infants actively seek information from a speaker regarding the referent of the speaker's utterance. Forty-eight infants (in three age groups: 1;2-1;3, 1;4-1;5, and 1;6-1;7) heard novel labels for novel objects in two situations: follow-in labelling (the experimenter looked at and labelled the toy of the infant's focus) vs. discrepant labelling (the experimenter looked at and labelled a different toy than that of the infant's focus). Subsequently, half of the infants were asked comprehension questions (e.g. 'Where's the peri?'). The other half were asked preference questions (e.g. 'Where's the one you like?'), to ensure that their comprehension performance was not merely the result of preferential responding. The comprehension results revealed developmental change in both (a) infants' ability to establish new word-object mappings (infants aged 1;2-1;3 failed to establish stable word-object links even in follow-in labelling), and (b) infants' ability to pinpoint the correct referent during discrepant labelling (only infants aged 1;6-1;7 succeeded). Thus the period between 1;2 and 1;7 represents a time of change in infants' ability to establish new word-object mappings: infants are becoming increasingly adept at acquiring new labels under minimal learning conditions.

Female↗
PubMed1993

Infants' ability to draw inferences about nonobvious object properties: evidence from exploratory play.

Generalizing knowledge about nonobvious object properties often involves inductive inference. For example, having discovered that a particular object can float, we may infer that other objects of similar appearance likewise float. In this research, exploratory play served as a window on early inductive capability. In the first study, 48 infants between 9 and 16 months explored pairs of novel toys in 2 test conditions: violated expectation (two similar toys were presented in sequence, the first toy produced an interesting nonobvious property, such as a distinctive sound or movement, while the second toy was invisibly altered such that it failed to produce the nonobvious property available in the first toy), and interest control (two similar-looking toys were presented in sequence, neither of which produced the interesting property). Infants quickly and persistently attempted to reproduce the interesting property when exploring the second toy of the violated expectation condition relative to the first toy of the interest control condition (a baseline estimate) or the second toy of the interest control condition (an estimate of simple disinterest). The second study, with 40 9-16-months-olds, confirmed these results and also indicated a degree of discrimination on infants' part: Infants seldom expected toys of radically different appearance to possess the same nonobvious property. The findings indicate that infants as young as 9 months can draw simple inferences about nonobvious object properties after only brief experience with just 1 exemplar.

Age Factors↗
PubMed1992

Clarifying the role of shape in children's taxonomic assumption.

When asked to find a new referent of a novel label children tend to ignore thematic relations (e.g., the relation between a spider and its web) and focus instead on taxonomic relations (e.g., the relation between a spider and a snake). The precise nature of children's taxonomic assumption has not been clear, however. One possibility is that the taxonomic assumption reduces to a "similar-shape rule": perhaps children tend to select objects of the same taxonomic kind when asked to extend new labels simply because these objects are more similar in shape than objects which are only thematically related. Sixty children between 3 and 5 years of age participated in three studies which examined children's attention to thematic relations, similarity of shape, and taxonomic relations when extending novel object labels. The findings indicated that shape has some primacy in children's expectations about object label reference, yet when shape is not available as a guide, children also take taxonomic kind into consideration when searching for new referents of novel labels. Thus children make use of a relatively rich and somewhat varied set of expectations to guide their inferences about object label reference.

Attention↗
PubMed1991

Infants' contribution to the achievement of joint reference.

This research examines whether infants actively contribute to the achievement of joint reference. One possibility is that infants tend to link a a label with whichever object they are focused on when they hear the label. If so, infants would make a mapping error when an adult labels a different object than the one occupying their focus. Alternatively, infants may be able to use a speaker's nonverbal cues (e.g., line of regard) to interpret the reference of novel labels. This ability would allow infants to avoid errors when adult labels conflict with infants' focus. 64 16-19-month-olds were taught new labels for novel toys in 2 situations. In follow-in labeling, the experimenter looked at and labeled a toy at which infants were already looking. In discrepant labeling, the experimenter looked at and labeled a different toy than the one occupying infants' focus. Infants' responses to subsequent comprehension questions revealed that they (a) successfully learned the labels introduced during follow-in labeling, and (b) displayed no tendency to make mapping errors after discrepant labeling. Thus infants of only 16 to 19 months understand that a speaker's nonverbal cues are relevant to the reference of object labels; they already can contribute to the social coordination involved in achieving joint reference.

Achievement↗
PubMed1990

The effects of anions on the kinetics of reductive elimination of iron from monoferrictransferrins by thiols.

The kinetics of reductive elimination of iron from the human serum monoferric transferrins by thioglycollate (TG), 3-mercaptopropionate (MP), cysteine (Cys), cysteamine (Cym) and 2-mercaptoethanol (ME) have been studied at 37 degrees C using bathophenanthroline sulphonate (BPS) as the ferrous ion acceptor. Analysis of the entire course of the reaction was possible only with thioglycollate since the other thiols cause eventual protein precipitation; in these cases, initial rates were used. The rate of iron release is linearly dependent on thiol concentration at low concentrations of reductant (less than approx. 0.2 M) and increases more rapidly with higher concentrations (up to 0.5-0.75 M). The thiols fall into two distinct groups, with TG, MP and Cys reacting at approx. the same rate, which is an order of magnitude faster than the reaction with Cym and ME. The carboxylate functionality present in the first group may be responsible for the faster reaction rate, by competitively weakening the interaction between the protein and synergistic anion. The pH-dependence of the rate of reductive elimination appears to depend on ionizable functionalities on both the protein and reducing agent. The addition of NaCl, NaClO4, NaHCO3 and Na2HPO4 increases the rate of iron release from the monoferric transferrins. The last two have particularly large accelerating effects and, in the case of the N-terminal monoferrictransferrin, gave saturation kinetics, suggesting that the observed effect is due to conformational changes in the protein caused by binding of ions. The role of the Fe-synergistic anion complex in the transferrins as a 'trapped intermediate' is considered.

3-Mercaptopropionic Acid↗
PubMed1989

Establishing word-object relations: a first step.

This work explores how infants in the early phases of acquiring language come to establish an initial mapping between objects and their labels. If infants are biased to attend more to objects in the presence of language, that could help them to note word-object object pairings. To test this, a first study compared how long 18 10-14-month-old infants looked at unfamiliar toys when labeling phrases accompanied their presentation, versus when no labeling phrases were provided. As predicted, labeling the toys increased infants' attention to them. A second study examined whether the presence of labeling phrases increased infants' attention to objects over and above what pointing, a powerful nonlinguistic method for directing infants' attention, could accomplish on its own. 22 infants from 2 age groups (10-14- and 17-20-month-olds) were shown pairs of unfamiliar toys in 2 situations: (a) in a pointing alone condition, where the experimenter pointed a number of times at one of the toys, and (b) in a labeling + pointing condition, where the experimenter labeled the target toy while pointing to it. While the pointing occurred, infants looked just as long at the target toy whether or not it was labeled. During a subsequent play period in which no labels were uttered, however, infants gazed longer at the target toys that had been labeled than at those that had not. Thus language can increase infants' attention to objects beyond the time that labeling actually occurs. These studies do not pinpoint which aspects of labeling behavior contribute to the attentional facilitation effect that was observed. In any case, however, this tendency for language to sustain infants' attention to objects may help them learn the mappings between words and objects.

Attention↗
PubMed1989

Priorities in children's expectations about object label reference: form over color.

Young children show considerable interest in color similarity; thus we might expect them to use color as a basis for generalizing object labels. However, natural language observations suggest they do not: children tend to overextend labels based on form similarity and rarely, if ever, overextend labels to objects that share only color. Perhaps, then, children give form priority over color in their expectations about object-label reference. This hypothesis was investigated in 2 studies. In a first study, 40 2- and 3-year-olds sorted 10 sets of 3 pictures that contrasted form with color. Children participated in 1 of 2 conditions: half of the children were shown a target object and asked to "find another one" from among the two choice objects, while the other children heard a novel label for the target (e.g., "See this zom?") and were asked to extend the label (e.g., "Can you find another zom?"). 3-year-olds sorted almost exclusively on the basis of form in both conditions, while 2-year-olds performed differently in the 2 conditions: they frequently chose the color match when labels were absent, but selected by form rather than color when asked to extend a novel label. A second study replicated these findings with novel objects that were real rather than pictured. This study also suggested that 3-year-olds grant color some role in their decisions about object-label reference as long as form differences are reduced to a tolerable level. In sum, young children expect form to be more important than color for guiding object-label reference, even though they may find color interesting when not asked to extend labels. This expectation helps explain the speed and relative ease with which children acquire object labels.

Attention↗
PubMed1987

Hemes and hemoproteins. 3. The reaction of microperoxidase-8 with cyanide: comparison with aquocobalamin and hemoproteins.

The monomeric heme octapeptide from cytochrome c, microperoxidase-8, (MP-8), coordinates CN- with log K = 7.55 +/- 0.04 at 25 degrees C in 20% (v/v) aqueous methanol. Log K values are independent of pH between 6 and 9. A spectrophotometric titration of cyanoMP-8 between pH 5.5 and 13.8 gave a single pKa greater than or equal to 13.5 ascribed to ionization of the proximal His ligand. A study of the kinetics of the reaction of MP-8 with cyanide between pH 5.5 and 12, at 25 degrees C and mu = 0.1, indicates that formation of cyanoMP-8 occurs via three routes: attack of CN- on Fe(III) (k1 = 6.0 +/- 0.3 X 10(5) M-1 sec-1); attack of HCN on Fe(III) (k2 = 4.8 +/- 2.0 X 10(3) M-1 sec-1), followed by deprotonation and isomerization to form the C-bound species; and displacement of OH- by CN- when the proximal His ligand is ionized (k5 = 1.8 +/- 0.1 X 10(5) M-1 sec-1). These results are compared with available data for the reaction of cyanide with aquocobalamin and with various hemoproteins.

Animals↗
PubMed1987

Hemes and hemoproteins. 5: Kinetics of the peroxidatic activity of microperoxidase-8: model for the peroxidase enzymes.

The peroxidatic activity of the heme octapeptide from cytochrome c, microperoxidase-8 (MP-8), was assayed at 25 degrees C under conditions where formation of Compound I is rate limiting. In the pH range 6-9, the reaction rate increased linearly with a slope close to unity. The active form of the substrate is the hydroperoxide anion, HO2-, and an extrapolated second-order rate constant was obtained for the reaction of aquoMP-8 with HO2- of 3.7 X 10(8) M-1 sec-1, which is close to the second-order rate constants reported for reaction of the peroxidase enzymes with H2O2. Comparison with published data shows that the Fe3+ ion of MP-8 reacts as expected with simple anions, electrons, and HO2-, while the analogous reactions of the enzymes all show a requirement for one H+. We conclude that the peroxidase enzymes activate H2O2 under physiological conditions through a pH-independent, H+-coupled binding of the required H2O2-. The peroxidase activity of MP-8 can be increased more than tenfold by the presence of the guanidinium ion, which is ascribed to formation of the ion-pair GuaH+HO2-; this suggests a role for the invariant distal Arg in the enzymes.

Animals↗
PubMed1986

Hemes and hemoproteins. 1: Preparation and analysis of the heme-containing octapeptide (microperoxidase-8) and identification of the monomeric form in aqueous solution.

The heme-octapeptide from cytochrome c, Microperoxidase-8 (MP-8), was prepared by peptic and tryptic digestion of horse heart cytochrome c and purified by gel permeation chromatography in about 50% yield. Conditions for the identification of MP-8 by TLC and analysis by HPLC are described. Study of the concentration-dependence of the absorption spectrum showed that at concentrations of less than or equal to 2.5 X 10(-5) M in aqueous solution at pH 7, 25 degrees C and mu = 0.1, MP-8 exists as an equilibrium mixture of monomers and dimers with KD = 1.17 +/- 0.02 X 10(5) M-1, decreasing to 1.21 +/- 0.02 X 10(4) M-1 and 2.16 +/- 0.21 X 10(3) M-1 in 20% and 50% (v/v) methanol:water mixtures, respectively. Comparison of the Soret region spectrum of monomeric MP-8 with other hemoproteins suggests that it is six-coordinate in aqueous solution with water and His as axial ligands.

Animals↗
PubMed1986

Hemes and hemeproteins, 2: The pH-dependent equilibria of microperoxidase-8 and characterization of the coordination sphere of Fe(III).

Titration of the monomeric heme octapeptide from horse heart cytochrome c, microperoxidase-8 (MP-8) from pH 1 to pH 13 in 20% (v/v) methanol-water solutions, mu = 0.1, at 25 degrees C shows three reversible concentration-independent pKs (4.43 +/- 0.09; 8.90 +/- 0.03; 10.48 +/- 0.09) which are ascribed to successive proton loss from the conjugate acid of His (and its coordination to Fe(III)), bound H2O, and from bound His to form an imidazolate complex, respectively. The equilibrium constant for coordination of imidazole between pH 5.5 and 7.0 is independent of pH (logK = 4.45) which proves that His-18 is coordinated to Fe(III) in aqueous solution.

Animals↗
PubMed1984

The effect of human serum transferrin and milk lactoferrin on hydroxyl radical formation from superoxide and hydrogen peroxide.

The effect of transferrins on hydroxyl radical formation from the superoxide anion and hydrogen peroxide generated by the xanthine-xanthine oxidase system has been studied by EPR using 5,5-dimethyl-1-pyrroline N-oxide as a spin trap. Neither diferriclactoferrin nor diferrictransferrin were found capable of promoting hydroxyl radical formation via the Haber-Weiss reaction even in the presence of EDTA in concentrations up to 1 mM. Activity observed by other authors may have been due to the presence of extraneous iron or an active protein impurity. Partially saturated transferrin and lactoferrin present in normal subjects may protect cells from damage by binding iron that might catalyze hydroxyl radical formation from superoxide and hydrogen peroxide. In any event, the hydroxyl radical formation observed in active neutrophils during phagocytosis cannot be associated with lactoferrin activity.

Apoproteins↗
PubMed1984

Protein-free models for the proton-coupled reduction of haemoproteins.

Reduction of the bis-pilocarpate-haemin complex at pH greater than or equal to 10 involves the simultaneous uptake of an electron by the Fe(III) ion and a proton by the pendant alkoxide group of an axial ligand. This provides a protein-free model for reactions such as the proton-coupled reduction of cytochromes which involve cooperative Coulombic interaction between two non-bonded sites.

Ferric Compounds↗