Within-event learning contributes to value transfer in simultaneous instrumental discriminations by pigeons

Following simultaneous discrimination training with pigeons, in which responding to the S−was reinforced on half of the trials and responding to the S− was never reinforced, we examined the effect on the S− of presenting the S− by itself and the effect on the S+ of presenting the S− by itself (relative to an S− or an S− for which there had been no single-stimulus presentations). For Group A−, responding to the S− presented by itself was always reinforced, whereas for Group A−, such responding was extinguished. For Group B−, responding to the S− presented by itself was always reinforced, whereas for Group B+, responding was extinguished. Although both Group A+ and Group A−tended to avoid their associated S− (relative to a control S−), Group A+ avoided its associated S− less than did Group A−. In contrast, although for Group B−, presentation of the S− alone increased the pigeons’ preference for its associated S−(relative to a control S+), for Group B−, presentation of the S−alone had little effect on its preference for its associated S+. These results suggest that presentation of one stimulus from a simultaneous discrimination has two independent and sometimes opposite effects on the other discriminative stimulus. First, it reduces the strength of within-event conditioning between the S+ and the S−, and second, if the value of the singly presented stimulus has increased, some of its newly acquired value will transfer retroactively to the stimulus with which it was originally paired.     

Temporal specificity in patterning of the rabbit nictitating membrane response

Rabbits were trained in either positive patterning (AX+, A−, X−) or negative patterning (A+, X+, AX−) using one of four intervals between the onset of A and the onset of X on AX trials. These intervals were 0, 800, 2,400, and 5,600 msec. In each task, all groups acquired an appropriate pattern of discriminative responding. Following acquisition, all rabbits were tested with the four different A-X intervals. All positive patterning groups showed an excitatory gradient, in which the highest level of responding occurred at the interval used in training. Conversely, all but one of the negative patterning groups showed an inhibitory gradient, in which the lowest level of responding occurred at the interval used in training. The one exception was the negative patterning group trained with simultaneous AX stimuli (0 msec), which showed a low, broad gradient, indicating transfer of inhibition across all the intervals. The results are discussed with respect to temporal encoding mechanisms and accounts of conditional discriminations.     

Multiple-pair training enhances transposition in pigeons

We studied transposition in pigeons by training them to select the smaller (or the larger) of a pair of circles. In training, different groups of pigeons were given one pair, two pairs, or three pairs of circles along the size dimension. Testing included two stimulus pairs for which, according to theoretical postdiscrimination generalization gradients, transposition should decrease from one-pair to two-pair to three-pair training. On the basis of the results of our earlier study (Lazareva, Wasserman, & Young, 2005) and contrary to these predictions, we expected that transposition should increase from one-pair to two-pair to three-pair training. We found that multiple-pair discrimination training enhanced transposition, which, on average, rose from 47% (one-pair training) to 52% (two-pair training) to 64% (three-pair training). In addition, we found that the overall similarity of the testing pair to the training pair(s) modulated the strength of relational responding. These results demonstrate that encountering multiple instances of a rule leads to stronger relational learning, even when reinforcement history predicts the opposite trend. These results also provide strong evidence against stimulus generalization as the sole determinant of relational responding in transposition.     

Determinants of value transfer and contrast in simultaneous discriminations by pigeons

In a simultaneous discrimination involving a positive (S+) and a negative (S₋) stimulus, positive value appears to transfer from the S+ to the S₋. However, negative value does not appear to transfer from the S₋ to the S+. Instead, when sufficient experience with the contingencies associated with responding to the S₋ is provided, it appears that the presence of the S₋ enhances the value of the S+ (i.e., a contrast effect is found). The purpose of the present experiments was to further examine the influence of the S+ on the S₋ in a simultaneous discrimination (between subjects in Experiment 1 and within subjects in Experiment 2). In both experiments, we found that under typical training conditions, given little direct experience with the value of the S₋, value transfers from the S+ to the S₋. If sufficient experience with the value of the S₋ is provided, however, contrast between the S+ and the S₋ can be demonstrated. Thus, in a simultaneous discrimination, value transfer from the S+ to the S₋ depends on the animal’s having responded relatively little to the S₋.     

Simultaneous discrimination learning: Stimulus interactions

Although considerable attention has been given to interactions between events serving as the positive (S+) and negative (S−) stimuli in successive discriminations, there has been little study of similar interactions in simultaneous discriminations. We propose that in a simultaneous discrimination, given what is typically relatively little experience with the consequences of responding to the S−, some of the value of the S+ transfers to the S− with which it was paired. Furthermore, the mechanisms responsible for this transfer of value appear to be the higher order Pavlovian association between the S− and the S+, as well as within-event associations between them. Although in typical simultaneous discriminations, negative value does not appear to transfer from the S− to the S+, when adequate experience is provided with the S−, contrast typically develops, reducing the value of the S− (negative contrast) and enhancing the value of the S+ (positive contrast). This model of stimulus interactions has implications not only for simple simultaneous discrimination learning, but also for research using combinations of discriminations (e.g., transitive inference in animals and humans). This model may also have implications for a number of human social psychological phenomena.     

Biases in pigeon working memory

The psychophysics and short-term retention of pigeons’ responses to rate of stimulus change were assessed in two experiments, using a symbolic delayed matching-to-sample procedure. In Experiment 1, the birds discriminated between steady and flickering lights. Psychophysical assessments of the discrimination suggested a mix of analogical and categorical strategies. Retention tests revealed a consistent bias to respond to the choice associated with theflickering sample. In Experiment 2, the birds discriminated between different rates of stimulus change (slow vs.fast). Retention tests indicated a bias to respond to the alternative associated with theslow sample. Transfer tests to new stimulus values revealed that the birds processed the stimuli in an absolute, rather than a relational fashion. These findings are related to recent work on biased forgetting in animal working memory experiments.     

Comparison of the effects of copper and lead on soil microbial biomass carbon and nitrogen in red soil

A laboratory incubation experiment was conducted to study the effect of copper as cupric sulfate (CuSO₄.5H₂O), and lead as lead acetate (Pb (OAc)₂) on the size of the microbial biomass in red soil. The metals were applied, separately at six different levels: Cu at 50, 100, 200, 300, 400, and 600 μg·g⁻¹ soil and Pb at 100, 200, 400, 600, 800, and 1000 μg·g⁻¹ soil. In comparison to uncontaminated soil, the microbial biomass carbon (C_mic) and biomass nitrogen (N_mic) decreased sharply in soils contaminated with Cu and Pb. The microbial biomass C:N ratio in the metal contaminated soil was observed to be considerably higher than that in untreated control. Between the two tested metals, Cu displayed greater biocidal effect on microbial biomass carbon and nitrogen than Pb, showing their relative toxicity in the order: Cu≫Pb. Project (No. 49671050) supported by National Natural Science Foundation of China. Wa’el Mohamad—Former Ph. D. Student of Zhejiang University and is working in Ministry Of Agriculture (P. O. box. 2099), Amman, Jordan.     

Permeation of dimethyl sulfoxide into articular cartilage at subzero temperatures

Osteochondral allografting has been proved to be a useful method to treat diseased or damaged areas of joint surfaces. Operational long-term stocks of grafts which supply a buffer between procurement and utilization would contribute to the commercialization or industrialization of this technology. Vitrification has been thought to be a promising method for successful preservation of articular cartilage (AC), but high concentration cryoprotectants (CPAs) are used which may cause high cellular toxicity. An effective way to reduce CPA toxicity is to increase CPA concentration gradually while the temperature is lowered. Understanding the mechanism of CPA permeation at subzero temperatures is important for designing the cryopreservation protocol. In this research, the permeation of dimethyl sulfoxide (Me₂SO) in ovine AC at subzero temperatures was studied experimentally. Pretreated AC discs were exposed in Me₂SO solutions for different time (0, 5, 15, 30, 50, 80, and 120 min) at three temperature levels (−10, −20, and −30 °C). The Me₂SO concentration within the tissue was determined by ultraviolet (UV) spectrophotometry. The diffusion coefficients were estimated to be 0.85×10⁻⁶, 0.48×10⁻⁶, and 0.27×10⁻⁶ cm²/s at −10, −20, and −30 °C, respectively, and the corresponding activation energy was 29.23 kJ/mol. Numerical simulation was performed to compare two Me₂SO addition protocols, and the results demonstrated that the total loading duration could be effectively reduced with the knowledge of permeation kinetics.     

A comparison of the Rescorla-Wagner and Pearce models in a negative patterning and a summation problem

In two experiments, we examined two related conditioning problems previously investigated by Red-head and Pearce (1995a) and Pearce, Aydin, and Redhead (1997). Experiment 1 involved an A+, B+, C+, AB+, AC+, BC+, ABC2 discrimination. The Rescorla-Wagner model predicts that response to AB, AC, and BC will be greater than that to A, B, and C at asymptote, whereas the Pearce model makes the opposite prediction. In Experiment 2, we investigated the responding to a novel ABC compound in groups trained with either A+, B+, C+ or AB+, AC+, BC+. The Rescorla-Wagner model predicts greater response to ABC in the group trained with A+, B+, C+ than in the group trained with AB+, AC+, BC+, whereas the Pearce model makes the opposite prediction. In contrast to the findings of Redhead and Pearce (1995a) and Pearce et al. (1997) in pigeon autoshaping, our findings in rabbit eyelid conditioning support the Rescorla-Wagner model.     

Synergistic interaction of NaCl and Cd on growth and photosynthetic parameters in soybean genotypes differing in salinity tolerance

The effects of salinity(50 mmol/L NaCl) and Cd(1 μmol/L CdCl2) as sole and combined on growth and photosyn-thetic parameters were studied using two soybean genotypes,Huachun 18 and NGB.The concentrations of Cd2 ,Zn2 ,Ca2 ,Mg2 ,K and Na were also determined in seeds and pods.Huachun 18 suffered a more serious decrease than NGB in net photosynthetic rate(Pn) in the treatments of salinity stress alone and combined stress(NaCl Cd),showing that it is relatively sensitive to salinity.The decrease in Pn caused by salt stress in Huachun 18 was mainly due to the reduced total chlorophyll content and photosynthetic efficiency(the ratio of variable fluorescence to maximal fluorescence,Fv/Fm),whereas the decease in NGB was mainly related to reduced stomatal conductance(Gs).The combined stress of both Na and Cd did not induce further decrease in photosynthesis and fluorescence in the two genotypes relative to salt or Cd stress alone.Greater change in the pod concentrations of Zn2 ,Ca2 ,Mg2 ,K and Na was detected under salt stress for Huachun 18 than for NGB.The results suggested that the interactive effect of NaCl-Cd on growth and nutrient uptake differs between the two soybean genotypes.     

Results on energies for trees with a given diameter having perfect matching

Let Γd2nbe the set of trees with a given diameter d having a perfect matching,where 2n is the number of vertex.For a tree T in Γd2n,let Pd+1be a diameter of T and q = d m,where m is the number of the edges of perfect matching inPd+1.It can be found that the trees with minimal energy in Γd2nfor four cases q = d 2,d 3,d 4,[d2],and two remarks aregiven about the trees with minimal energy in Γd2nfor2d 33q d 5 and [d2] + 1 q2d 33 1.     

Acquisition and extinction of facilitation in the C57BL/6J mouse

Acquisition, extinction, and transfer of facilitation were explored in a series of experiments with C57BL/6J mice. With a procedure in which an auditory target was followed by food only in the presence of a visual facilitator, Experiments 1—4 showed that the facilitator promoted magazine entries to the auditory target. This enhancement effect was eliminated by training the facilitator as a conditioned inhibitor (Experiments 1 and 3B). Enhancement was also reduced by nonreinforced presentations of the facilitator in a discrimination procedure (Experiment 1) and by simple nonreinforcement of the facilitator (Experiments 2, 3A, and 4). In contrast to the results obtained with a facilitator, simple nonreinforcement of an inhibitor, a visual cue that had signaled when an auditory target would not be reinforced, did not reduce its ability to modulate responding to that target (Experiment 4). However, both the facilitator and the inhibitor were found to transfer their modulatory effects to other targets (Experiment 4). Finally, mice demonstrated no evidence of differential responding on a biconditional discrimination procedure in which one auditory target (A1) was reinforced in the presence of one visual stimulus (L1) but not in the presence of another (L2), and a different auditory target (A2) was reinforced in L2 but not in L1 (Experiment 5). The implications of these results for analysis of the function of a facilitator are discussed.     

Infrared Absorption Spectra of Serpentine Cat＇s Eye from Sichuan Province of China

Infrared （IR） absorption spectra and X-ray powder diffraction （XRD） patterrns of sexpenfine cat＇s eye from Sichuan Province have been investigated, and infrared absorption bands of the serpentine have been assigned in this paper. The results indicate that the bands near 3 600 - 3 700 cm^-1 belong to the stretching absorption band VOH, the bands in 948 - 1 100 cm^-1 axe assigned to the stretching vibraling band Usvo, and the bands at 600 570 and 440 cm^-1 respectively belong to the bending vibration band VOH, δMg-O and δSi-O. The serpentine cat＇ s eye includes two types： chrysotile and antigorite. Chrysotile has a sharp and intensive band at 3 688 cm^-1 and a weak band at 3 643 cm^-1 , while antigorite has only one intensive band in the region. At vibration band VSi-O, chrysotile and antigorite have a similar feature at 1 071 cm^-1, but the band at 980 cm^-1 in anfigorite has been split into two bands in chrysotile - a strong one at 1 027 cm^-1 and a weak one at 949 cm^-1. In addition, antigorite has a characteristic bending vibrating band δMg-O at 570 cm^-1. Based on the analysis of the feature of crystal structure, their IR differences axe well explained.     

Determination of Trace Molybdenum（VI） by Oscillographic Potentiometric Catalyzing Kinetic Method of Simplex Optimization

1　Introduction　Ahugeamountofliteratureexistsonthestudyofi dentifyingtracemetalionsbymeansofspectropho tometry[1 3] ,fluorimetry[4 6 ] aswellas polarogra phy[7 9] ,whichhaveactiononlocatingtheendpointoftheindicatingreaction .Howeverbothspectropho tometryandfluorimetryareeasytobeinterferedbycolororprecipitation ,whilepolarographyhasanissueofmercurypollution .Thecatalyzingkineticanalysishasthecharacteristicsofhighsensitivityandspeedi ness.Oscillographicpotentiometryisasimpleintu itionisticanal…     

Productive knowledge of derivational rules in poor readers

The present report with two complementary experiments examined the productive knowledge of derivational morphology in 75 grade 4, 5, and 6 “poor” readers further divided into those performing better, or worse, inboth reading and spelling ((R + S +) or R − S −)), or better in the one or the other (mixed) subgroups. Experiment 1 required individual subjects to vocalize rapidly the derived forms of words when primed with 40 target base words in four derivational conditions or levels embedded in sentence frames shown on the computer screen. Experiment 2 required the reverse process of vocalizing the base forms of words when primed with 40, complex derived forms in the same four morphology conditions embedded in sentence frames shown on the computer screen. Results of the analysis of the reaction times show a developmental trend and that the subgroups of poor readers used different mechanisms in producing derived or base forms of words according to the complexity of the orthographic and/or phonological changes needed in the derivational process. The important role of morphemic structure and origin of words in instruction is emphasized.     

Teasing out repetition from rote: an essay on two versions of will

In some circles of mathematics education, repetition and rote are somehow conflated in terms of their pedagogical uses and ramifications. In this paper, I argue for the separation of the two, relying upon a framework suggested by Martin Buber’s I–Thou ontology. In the presentation of Buber’s ideas, I highlight the notion of will-as-would-join-with-grace, to be contrasted with plain will. The merit of repetition in teaching and learning, as I argue, is not in automaticity—the common rationale—but in fostering and supporting a deepened sense of connection and/or intimacy to the object under study.     

Semi On-line Scheduling Problem for Maximizing the Minimum Machine Completion Time on m Identical Machines

In this paper, a semi on-line version on m identical machines M1 , M2, …, Mm ( m ≥ 3 ) was considered, where the processing time of the largest job is known in advance. Our goal is to maximize the minimum machine load, an NPLS algorithm was presented and its worst-case ratio was proved to be equal to m - 1 which is the best possible value. It is concluded that if the total processing time of jobs is also known to be greater than (2 m - 1 )Pmax where pmax is the largest job‘s processing time, then the worstcase ratio is 2 - 1/m.     

Preparation of SO4^2-/TiO2-La2O3 solid superacid and its catalytic activities in acetalation and ketalation

SO4^2- / TiO2-La2O3, a novel solid superacid, was prepared and its catalytic activities at different synthetic conditions are discussed with esterification of n-butanoic acid and n-butyl alcohol as probing reaction. The optimum conditions have also been found, mole ratio of n（La^3＋）：n（Ti^4＋） is 1：34, the soaked consistency of H2SO4 is 0.8 tool/L, the soaked time of HESO4 is 24 h, the calcining temperature is 480 ℃, the calcining time is 3 h. Then it was applied in the catalytic synthesis often important ketals and acetals as catalyst and revealed high catalytic activity. Under these conditions on which the molar ratio of aldehyde/ketone to glycol is l： 1.5, the mass ratio of the catalyst used in the reactants is 0.5%, and the reaction time is 1.0 h, the yields of ketals and acetals can reach 41.4%-95.8%.     

Chemically processed Nb-doped SrTiO3 films and properties

Homogeneous, crack-free SrNb_xTi_1−x O₃ thin films on (110) silicon substrates were successfully fabricated by sol-gel processing. The optimum route and conditions were systematically investigated. Sr(OAc)₂ glacial acctic acid solution, after being refluxed and reacted with tartrate, formed Sr(OAc)₂(C₄H₆O₆)₂; Ti(OBu)₄ formed Ti(OAc)_4−x (AcAc)_x after having the ligand partially exchanged with AcAc, while Nb(OC₂H₅)₅ formed (OAc)₂Nb(AcAc) (C₄H₆O₆) by exchanging of ligand in glacial acetic acid with (CH₃CO)₂O. All the metal species after undergoing partial hydrolysis and polymerization with hydroxyl or oxygen, formed SrNb_xTi_1−x O₁₃ cluster sol. Methyl cellulose (MCL) caused SrNb_xTi_1−x O₃ sol to have polymeric structure and easily form films. SrNb_xTi_1−x O₃ films with perovskite were subsequently formed after being annealed at 650∼750 °C for 60 min in 25% N₂+75% H₂ (volume ratio) atmosphere. Resistivity of the SrNb_0.1Ti_0.9O₃ films at room temperature was 64 μω·cm, a particular T ² temperature dependence of the resistivity, from 25 K up to room temperature, was observed. Project (No. 2002CB613305) supported by the National Basic Research Program (973) of China