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.     

Failure to obtain value enhancement by within-trial contrast in simultaneous and successive discriminations

The present research tested the generality of the “work ethic“ effect described by Clement, Feltus, Kaiser, and Zentall (2000). In Experiment 1, we trained 10 pigeons on a pair of either simultaneous or successive discriminations. One discrimination followed a high-effort requirement (20 pecks to the center key) and the other followed a low-effort requirement (1 peck). Contrary to Clement et al.’s results, we found that preferences between the S⁺ and S⁻ stimuli in transfer tests depended on the event that initiated the trial: Pigeons preferred the stimulus from the baseline discrimination whose initiating event was most dissimilar from that preceding the test trial. Preferences were similar but less extreme in the successive condition. In Experiment 2, we investigated whether test preferences depended on the amount of training. A total of 12 pigeons were trained on a pair of simultaneous discriminations, except that test sessions were scheduled after every three baseline sessions. Preferences increased across test sessions but were similar to those in Experiment 1. Together with Vasconcelos, Urcuioli, and Lionello-DeNolf (2007a), our study represents a second failure to replicate Clement et al.’s work ethic effect. The finding that preference depends on the event that initiates the test trial suggests that choice probes may not provide unambiguous assessments of stimulus value.     

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.     

Value transfer in a simultaneous discrimination by pigeons: The value of the S+ is not specific to the simultaneous discrimination context

During simultaneous discrimination training, there is evidence that some of the value of the S⁺ transfers to the S^?. When the value of the S+ is altered outside the context of the simultaneous discrimination, two very different predictions are made concerning its effect on its S^?, depending on whether one views the S⁺ as an occasion setter or as a stimulus capable of transferring value. In four experiments, pigeons were trained with two similar simultaneous discriminations, A⁺B^? and C⁺D^?, and two single-stimulus trial types, A and C, (in which A always had greater nominal value than C). According to value transfer theory, on test trials, B should always be preferred over D, because B and D should be affected by the net values of A and C, respectively. According to an occasion setting account, however, D should be preferred over B because the presence of D signals a higher probability of reinforcement for responding to C than when C is alone, and/or the presence of B signals a lower probability of reinforcement for responding to A than when A is alone. In all four experiments, the pigeons preferred B over D, a result consistent with value transfer theory. Thus, an S^? can acquire value from an S⁺ even when that value is conditioned in a “context” different from that of the simultaneous discrimination.     

Deprivation level and choice in pigeons: a test of within-trial contrast

Within-trial contrast has been proposed as a mechanism underlying preferences for stimuli that follow relatively more aversive events over stimuli that follow less aversive events. In this study, we manipulated deprivation level to test within-trial contrast predictions. In Experiment 1, pigeons encountered two discriminative stimuli, one presented when they were deprived and the other when they were prefed. When later given a choice between the two stimuli, pigeons strongly preferred the stimulus encountered when deprived, independently of their deprivation level at test. In Experiment 2, pigeons learned two simultaneous discriminations, one when deprived and the other when prefed. Here, subsequent tests between the two S⁺ or the two S⁻ stimuli revealed no consistent preferences. These contrasting findings suggest that differential aversiveness is necessary but not sufficient to induce preferences via within-trial contrast.     

Discrimination blocking: Acquisition versus performance deficits in human contingency learning

We compared acquisition and performance accounts of human contingency learning. After solving a discrimination in Phase 1, in which Cue A predicted the occurrence of the outcome and Cue B predicted its nonoccurrence (A+/B−), a new discrimination (X+/Y−) was superimposed in Phase 2 (AX+/BY−). The participants were finally trained in Phase 3 with the added discrimination, which either maintained the same contingencies as those in Phase 2 (X+/Y−; Experiment 1) or reversed the contingencies (X−/Y+; Experiment 2). According to competitive-learning theories (e.g., Rescorla & Wagner, 1972), there should be no learning of the added discrimination in Phase 2, so that no advantage or disadvantage for this discrimination should be observed in Phase 3. In contrast, performance theories, such as the comparator hypothesis (Miller & Matzel, 1988), contend that learning of the added discrimination in Phase 2 should proceed normally; so, in Phase 3, an advantage for the added discrimination should be observed in Experiment 1, but a disadvantage should be observed in Experiment 2. Our participants learned about the added discrimination and generally showed the effects predicted by the comparator hypothesis.     

Effect of odor preexposure on acquisition of an odor discrimination in dogs

In two experiments, we investigated the impact of odor preexposure treatments on the acquisition of an olfactory discrimination in dogs. In the first experiment, four groups of dogs were each given five days’ odor-exposure treatment prior to discrimination training. Dogs in the exposure group were exposed to anise extract (S+) for 30 min daily. Dogs in the Pavlovian-relevant pairing group received six daily delayed-conditioning trials to the same S+. The Pavlovian-irrelevant pairing group received conditioning trials to almond extract (S'). Dogs in the control group received no pretreatment. All of the dogs were then trained to detect S+ from a background pine odor (an AX-vs.-X discrimination). The Pavlovian-relevant pairing group acquired the odor discrimination significantly faster than all of the other exposure and control groups, and the remaining groups acquired the discrimination at the same rate as the no-exposure control group. In a second experiment, we extended these results to a within-subjects design using an AX-versus-BX discrimination. Six dogs were simultaneously trained on two different odor discriminations, one discrimination in which the S+ was previously Pavlovian conditioned, and one discrimination in which the S+ was novel. All of the dogs learned the odor discrimination with the previously conditioned S+ faster than they learned the novel odor discrimination, replicating the results of Experiment 1, and demonstrating that familiarity in the form of Pavlovian conditioning enhances odor-discrimination training. The potential mechanisms of the facilitated transfer of a Pavlovian conditioned stimulus to discrimination training are discussed.     

Differential inhibition and stimulus generalization cannot account for value transfer in simultaneous discrimination learning by pigeons: Reply to Aitken

Aitken (1999) argues that, in a simultaneous discrimination, reports of the transfer of value from the positive to the negative stimulus can be more readily explained in terms of an artifact produced by the procedure in which differential inhibition accrues to the negative test stimuli during training, together with stimulus generalization (similarity between the positive and negative stimuli). We argue that (1) there is little evidence for differential inhibition, and it often occurs in the wrong direction; (2) value transfer can be demonstrated when differential value is established to the positive stimuli afterdiscrimination training, when differential inhibition is not likely to be a factor; and (3) on both logical and empirical grounds, stimulus similarity does not provide an adequate account of the transfer of value from the positive to the negative stimulus (i.e., the strongest evidence for value transfer occurs when there is least stimulus similarity). We propose that value transfer occurs whenever there is relatively little experience with the negative stimuli. However, when there is extended experience with the negative stimuli, contrast will be found.     

Assessment of semi-empirical mass transfer correlations for pervaporation treatment of wastewater contaminated with chlorinated hydrocarbons

INTRODUCTION Chlorinated hydrocarbons, a class of widely used dry-cleaning liquids, industrial organic solvents, and degreasers, increasingly find their way into drinking water sources, thus posing a very serious health and environmental problem (Love and Eliers, 1982). These organic solvents are known for their stability in the environment and cancer-causing po- tency and cannot be effectively and economically eliminated by current conventional treatment tech- nologies. One of the few av…     

Congruences for finite triple harmonic sums

Zhao (2003a) first established a congruence for any odd prime p>3, S(1,1,1;p)≡-2Bp-3 (mod p), which holds when p=3 evidently. In this paper, we consider finite triple harmonic sum S(α,β,γ;p) (mod p) is considered for all positive integers α,β,γ. We refer to w=α β γ as the weight of the sum, and show that if w is even, S(α,β,γ;p)≡0 (mod p) for p≥w 3; if w is odd, S(α,β,γ;p)≡rBp≥w (mod p) for p≥w, here r is an explicit rational number independent of p. A congruence of Catalan number is obtained as a special case.     

Regular-singular crossings on nonlinear systems with turning point

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Transposition in pigeons: reassessing spence (1937) with multiple discrimination training

We studied transposition in pigeons, using multiple-pair discrimination training. Four birds discriminated two pairs of circles: 1+ 2− and 5+ 6− or 1− 2+ and 5− 6+ (digits denote circle diameters and plus and minus signs denote reward and nonreward, respectively). Four other birds discriminated four pairs of circles: 1+2−, 1+3−, 4+6−, and 5+6−or 1−2+, 1−3+, 4−6+, and 5−6+. Finally, 4 birds discriminated only one pair of circles: 1+ 2−, 1+ 2−, 5+ 6−, or 5− 6+. Testing included five new pairs—1/5, 2/3, 2/6, 3/4, and 4/5—that distinguished absolute from relational accounts of transposition. The pigeons’ relational responding rose from one- to two- to four-pair training. The similarity of the testing stimuli to one another also affected relational responding: Transposition increased with highly dissimilar stimuli. Neither Spence’s (1937) theory nor existing relational accounts could predict the obtained pattern of relational responding.     

Transitive inference in pigeons: Simplified procedures and a test of value transfer theory

Minimal procedures for the demonstration of transitive inference (TI) in animals have involved the training of four simultaneous discriminations: for example, A+B?, B+C?, C+D?, and D+E?, followed by the demonstration of a preference for B over D on test trials. In Experiment 1, we found that TI in pigeons can be found with successive training involving A+B?, B+C?, A+C?, C+D?, D+E?, C+E?, and A+E?. In Experiment 2, we found that demonstration of TI did not require inclusion of experience with the nonadjacent stimulus pairs (A+C?, C+E?, A+E?). Experiment 3 provided a test of value transfer theory (VTT; Fersen, Wynne, Delius, & Staddon, 1991). When pigeons were trained with stimulus pairs that did not permit the transitive ordering of stimuli, but did permit the differential transfer of value (e.g., A+B?, C?E+, C+D?, & A+E?), preference for B over D was still found. Analyses of the relation between direct experiences with reinforced and nonreinforced responding and stimulus preferences on test trials failed to support a reinforcement-history account of TI.     

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.     

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.     

Scaling behavior of nucleotide cluster in DNA sequences

In this paper we study the scaling behavior of nucleotide cluster in 11 chromosomes of Encephalitozoon cuniculi Genome. The statistical distribution of nucleotide clusters for 11 chromosomes is characterized by the scaling behavior of P（S） ∝ e^-αs＇ where S represents nucleotide cluster size. The cluster-size distribution P（S1＋S2） with the total size of sequential C-G cluster and A-T cluster S1＋S2 were also studied. P（S1＋S2） follows exponential decay. There does not exist the case of large C-G cluster following large A-T cluster or large A-T cluster following large C-G cluster. We also discuss the relatively random walk length function L（n） and the local compositional complexity of nucleotide sequences based on a new model. These investigations may provide some insight into nucleotide cluster of DNA sequence.     

Retrospective and prospective short-term memory in delayed response tasks in rats

Separate groups of rats were trained and tested on asymmetrically and symmetrically reinforced successive delayed matching-to-sample (DMTS) or delayed discrimination (DD) tasks in Experiment 1. Each rat received training and testing on symmetrically reinforced DMTS and DD tasks in Experiment 2. The only difference between each task was that the rats had to respond correctly to a light or tone test stimulus, S₂, if it matched a light or tone sample stimulus, S₁, in DMTS, but could respond to either S₂ if S₁ had been a particular stimulus in DD. Only correct leverpresses were reinforced in the asymmetrically reinforced version of each task. Both correct presses and correct omissions were reinforced in the symmetrically reinforced version of each task. Response biases to leverpress during tests for delayed responding to S₁ were reduced in both symmetrically reinforced tasks, but only in the DD task did such contingencies produce consistently poorer performance in responding to either S, in Experiment 1. Declines in accuracy of performance that occurred in both experiments were greater to the visual than to the auditory S₁ only in the DMTS tasks with increased intervals between S₁ and S₂. A third experiment, in which rats had to respond to S₂ if it matched S₁ (DMTS) or if S₂ mismatched S, (DMmTS), was carried out. Modality of S₁ similarly affected accuracy of delayed responding in each task, as in the first two experiments. Methodological and theoretical implications of these results are discussed in terms of Honig and Thompson’s (1982) dual-process theory of working memory.     

Sensitized Up—Conversion Luminescence of Ho^3＋ in Nd^3＋—Yb^3＋—Ho^3＋ Co—doped ZrF4—Based Glass

Up-conversion processes for the blue, green and red emissions were found two-photon phenomenon, known as the cooperative phenomenon. This phenomenon was assisted by Nd³⁺ → Yb³⁺ → Ho³⁺ energy transfer. The strong green emission due to the Ho³⁺ : (⁵F₄, ⁵S₂)→ ⁵I₈ transitions was observed in Nd³⁺-Ho³⁺ co-doped ZrF₄-based fluoride glasses under 800 nm excitation. As an attempt to enhance Ho³⁺ up-conversion luminescences in the Nd³⁺ – Ho³⁺ co-doped ZrF₄-based glasses, Yb³⁺ ions were added to the glasses. As a result it was found that, in 800 nm excitation of 60 ZrF₄. 30BaF2. (8-x)LaF₃. lNdF₃. xYbF₃. 1HoF₃ glasses (x=0 to 7), sensitized up-conversion luminescences are observed at around 490 nm (blue), 545 nm (green), and 650 nm (red), which correspond to the Ho³⁺ : ⁵F₃ → ⁵I₈, ( ⁵F₄, ⁵S₂)→⁵I₈ and ⁵F₅→ ⁵I₈ transitions respectively. The intensities of the green and red emissions in a 3 mol % YbF₃-containing glass were about 50 times stronger than those glasses without YbF₃. This is based on sensitization due to Yb³⁺ ions. In particular, the green emission was extremely strong and the Nd³⁺-Yb³⁺-Ho³⁺ co-doped ZrF₄-based glasses have a high possibility of realizing a green up-conversion laser glass. In this paper the up-conversion mechanism in the glasses is discussed in detail.     

过冷液相区内轧制温度对Zr52.5Al10Ni10Cu15Be12.5大块金属玻璃表面形貌的影响

Surface morphologies of Zr52.5 Al10 Ni10 Cu15 Be12.5 bulk metallic glass after being rolled at both a temperature around T9 and near （ Tx - 50） K were investigated with a scanning electron microscopy. Macroscopic and microscopic observation results show that squamae, cracks, steps and wedges exist on the surface when the samples were rolled at temperatures around Ty. However, a smooth and fiat surface appears when the samples were rolled at temperatures near （ Tx - 50） K. These results indicate that the mode of deformation in the supercooled liquid region is a partially homogeneous flow at a temperature around T9, and a fully homogeneous one at temperatures near （ Tx - 50） K. According to the results, it is more feasible to roll the amorphous alloys at temperatures near （ Tx - 50） K to obtain parts with smooth and fiat surface.     

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.