Memory codes for temporal and nontemporal samples in many-to-one matching by pigeons

Pigeons were trained to match temporal (2 and 8 sec of keylight) and color (red and green) samples to vertical and horizontal comparison stimuli. In Experiment 1, samples that were associated with the same correct comparison stimulus displayed similar retention functions; and there was no significant choose-short effect following temporal samples. This finding was replicated in Phase 1 of Experiment 2 for birds maintained on the many-to-one mapping, and it was also obtained in birds that had been switched to a one-to-one mapping by changing the comparison stimuli following color samples. However, in Phase 2 of Experiment 2, when the one-to-one mapping was produced by changing the comparison stimuli following temporal samples, a significant choose-short effect was observed. In Experiment 3, intratrial interference tests gave evidence of temporal summation effects when either temporal presamples or color presamples preceded temporal targets. This occurred even though these interference tests followed delay tests that failed to reveal significant choose-short effects. The absence of significant choose-short effects in Experiment 1 and in Phase 1 of Experiment 2 indicates that temporal samples are not retrospectively and analogically coded when temporal and nontemporal samples are mapped onto the same set of comparisons The interference test results suggest that the temporal summation effect arises from nonmemorial properties of the timing system and is independent of the memory code being used     

Coding of hedonic and nonhedonic samples by pigeons in many-to-one delayed matching

In two experiments, pigeons were trained on many-to-one delayed matching in which samples of food and one hue were each associated with one shape comparison, and samples of no food and a different hue were each associated with a second shape comparison. When later tested with delays between sample and comparison stimuli, pigeons showed nonparallel delay functions, typically found with food and no-food samples (i.e., steeply declining food-sample delay functions, and relatively flat no-food-sample delay functions). Furthermore, the slopes of the hue-sample delay functions were similar to those on the food/no-food-sample trials. In Experiment 2, following many-toone delayed matching, when the hue samples were associated with new comparisons and then food and no-food samples replaced the hues, evidence was found for transfer of training indicative of the common coding of samples associated with the same comparison in original training. The transfer results suggest that the asymmetrical hue-sample functions resulted from the common coding of samples associated with the same comparison.     

Common coding by pigeons in a many-to-one delayed matching task as evidenced by facilitation and interference effects

Pigeons were first trained on many-to-one delayed matching in which pairs of hue and line-orientation samples were associated with individual comparison stimuli. They were then trained to match two of the original samples (either hues or line orientations) to new comparisons, after which 2-sec delays were inserted between the samples and comparisons. In testing, the remaining samples were presented as interpolated stimuli during the delays. When the interpolated stimulus had been associated with the same comparison as the sample in many-to-one matehing, performance was significantly more accurate than when it had been associated with a different comparison. This finding adds to the evidence that samples sharing common comparison associations are commonly coded.     

Rats exhibit asymmetrical retention functions for hedonic and nonhedonic samples in many-to-one symbolic delayed matching to sample

Rats were initially trained in a symbolic delayed matching-to-sample task either to discriminate hedonic samples that consisted of food or no food or to discriminate tone samples that differed in frequency and location. The retention functions for both the hedonic and tone samples were asymmetric, with forgetting of the food sample or the high-frequency tone occurring more rapidly than forgetting of the no-food sample or the low-frequency tone. Next, many-to-one (MTO) training was given in which tone samples were added for the rats initially trained with hedonic samples, and hedonic samples were added for the rats initially trained with tone samples. For both groups, a food sample and a tone sample (tone-F) were associated with responding to one lever (e.g., stationary), and a no-food sample and a different tone sample (tone-NF) were associated with responding to the alternative lever (e.g., moving). During retention testing, we found equivalent forgetting for the food and no-food samples, but forgetting of the tone-F sample occurred more rapidly than forgetting of the tone-NF sample. This is the first MTO study to suggest that rats, like pigeons, may use hedonic samples as the basis for the common coding of nonhedonic samples in MTO delayed matching.     

Some tests of the anticipatory mediated generalization model of acquired sample equivalence in pigeons’ many-to-one matching

Transfer-of-control tests typically show the development of acquired equivalence between samples occasioning the same comparison choice in pigeons’ many-to-one matching-to-sample. Specifically, when some of those samples are later explicitly trained to occasion new comparison choices, the remaining samples immediately exert control over the new choices as well. In the present experiments, we examined whether or not this transfer effect depends on the order in which the various sample-comparison relations in training are learned. One group of pigeons initially acquired 0-delay many-to-one matching with four samples and two comparisons, followed by 0-delay matching with two of those samples and two new comparisons. Another group of pigeons learned the two-sample matching task first, followed by many-to-one matching. When subsequently tested for their ability to match the remaining samples from many-to-one matching to the comparisons used in the two-sample task, both groups showed comparable levels of transfer. These findings challenge the view that common anticipatory processes ostensibly arising from the samples in many-to-one matching are necessary mediators for the subsequent transfer effects indicative of acquired sample equivalence.     

The role of test stimuli in matching to compound samples by pigeons

Two pigeons matched to sample in a three-key operant conditioning chamber. In Experiment I, two different kinds of samples were presented on the center key.Element samples were members of one of two sample sets — colors (a red or blue disk) or lines (a vertical or horizontal orientation of a set of white lines). These samples were followed by their respective sample sets on the side keys as comparison stimuli.Compound samples consisted of a set of lines superimposed on a colored disk. Following these samples, either sample set could appear as comparison stimuli. Matching to compound samples was less accurate than matching to element samples. One interpretation is that sharing of attention among elements of a compound sample weakened stimulus control by each element. A different interpretation is that an element sample controlled matching better because it was physically identical to a comparison stimulus whereas a compound sample was not. Experiments II–IV evaluated this “generalization decrement” alternative by testing element- vs. compound sample control with both element and compound comparison stimuli. Irrelevant elements were added to form compound comparison stimuli, some of which were physically identical to a preceding compound sample, but never identical to an element sample. In all experiments, the addition of irrelevant elements of comparison stimuli reduced sample control. However, the generalization decrement hypothesis failed to predict how differences in performance maintained by element and compound samples were affected by different tests of sample control. Matching accuracy appeared to be independently determined by the number of elements in a sample and whether irrelevant elements were present during tests of sample control.     

Absence of immediate transfer of training of duration symbolic-matching-to-sample in pigeons

Two experiments examined the performance of pigeons on symbolic-matching-to sample in which the relevant sample dimension consisted of duration. Each pigeon was trained on two problems that had the same two sample durations, 2 and 10 sec, but were different with respect to other physical properties of the samples. Durations of light and tone were used in Experiment 1; durations of two different color-location compounds were used in Experiment 2. In each experiment, a unique choice stimulus was associated with each of the four possible combinations of duration and signal type. Test sessions contained probe trials in which the choice stimuli were these appropriate for a long and a short duration of the signal type opposite to that actually presented. Pigeons in both experiments displayed asymmetrical performance deficits. Accuracy on long durations dropped to chance or below, whereas accuracy on short durations remained high. This pattern is similar to the choose-short effect that is obtained when animals are tested with long retention intervals. The implications of these results for duration memory, coding, and transfer of training are discussed.     

Delayed matching in pigeons with food and no-food samples: Further examination of backward associations

When pigeons are trained on a delayed conditional discrimination with presence versus absence samples and tested with delays, a bias to choose the comparison associated with the absence sample is observed with increasing delay. Additionally, when the samples consist of food versus no food, this trial-type performance difference is reversed on short-delay trials: a bias to choose the comparison associated with the presence sample develops with delay testing. This reversal in comparison bias at short delays has been attributed to a preference produced by backward associations between the hedonic samples and the nonhedonic choice stimuli. In the present experiment, we tested an alternative hypothesis, that the short-delay comparison bias is produced by proactive interference—in particular, from reinforcement obtained on the previous trial—by including a group trained with reinforcement on only half of the trials with a correct response. According to the proactive interference account, this group should have shown a smaller short-delay comparison bias than would the typical 100% reinforcement group. Instead, consistent with a backward-association interpretation, the magnitude of the short-delay comparison bias shown by the 50% group was significantly greater than that shown by the 100% group.     

Flexible coding of temporal information by pigeons: Event durations as remember and forget cues for temporal samples

The ability of pigeons to use event durations as remember (R) and forget (F) cues for temporal samples was examined. Pigeons were required to indicate whether a houselight sample stimulus was short (2 sec) or long (6 sec) by pecking a red or a green comparison stimulus. After training with a constant 10-sec delay interval, temporal cues (illumination of the center key) were presented 2 sec after the offset of the temporal samples. For one group, a short (2-sec) temporal cue served as the R cue and a long (6-3ec) temporal cue served as the F cue. This was reversed for a second group of birds. During training, comparison stimuli were always presented following the temporal R cue, but never following the temporal F cue. Tests for the effectiveness of the temporal R and F cues showed that F cues were equally effective in reducing matching accuracy in both groups of birds. It was concluded that pigeons used the duration of the cue to determine whether or not to rehearse the memory code for the temporal sample.     

Memory for duration in pigeons: Dissociation of choose-short and temporal-summation effects

Five groups of pigeons were trained in a symbolic choice-matching feast involving short (2-sec) and long (10-sec) durations of houselight as samples. Four groups also received training with a second set of samples: line orientations or 2- and 10-sec presentations of keylight. The type of sample-to-comparison mapping varied across groups. Although only two of the five groups demonstrated a choose-short effect (a tendency to choose the comparison associated with a short sample at longer delays), all groups demonstrated temporal summation (a tendency to respond on the basis of the combined duration of two successively presented samples). Moreover, the magnitude of temporal summation was equivalent in groups that did and did not-demonstrate a choose-short effect. The results suggest that the processes underlying the perception of sample duration remain invariant across different sample-to-comparison mapping arrangements, but that the memory code used to retain temporal information varies.     

An evaluation of the role of dual coding in mediating the effect of incorrectly cuing the comparison dimension in delayed matching in pigeons

Pigeons were trained on delayed matching-to-sample trials in which red and green sample stimuli were equally often followed by color comparisons and by line-orientation comparisons. The color samples were preceded and accompanied by cues (a triangle or a black dot) that signaled whether the comparisons on that trial would be colors or lines. Length of the retention interval was manipulated during testing, and probe trials were included on which the dimension of the comparison stimuli either was cued incorrectly or was not cued. Accuracy on incorrectly cued and on no-cue trials was less than that on correctly cued trials, and the magnitude of this effect was not influenced by the length of the retention interval. Accuracy on incorrectly cued and on no-cue trials was equivalent, and was greater than chance. The data are inconsistent with two dual-coding interpretations of the effects of incorrectly cuing the dimension of the comparison stimuli in which it is held that both retrospective and prospective sample coding occurs in this task.     

The effects of sodium pentobarbital on matching and oddity performance in pigeons

The effects of sodium pentobarbital on matching and oddity performance in pigeons were examined by employing a higher-order conditional discrimination paradigm. In this paradigm, the line orientation which was superimposed on all of the response keys signaled whether a response to the matching color or a response to the nonmatching color was correct. All pigeons had extensive previous training in this paradigm and were tested at each of three dosage levels: 5, 7.5, and 10 mg/kg. For all birds, a clear dose-related decrease in accuracy was observed; however, the effect was not differential for matching and oddity trials. Accuracy reductions were accompanied by an increase in position preference on both types of trials. The data are compatible with recent claims that physical identity of the sample and correct comparison stimulus need have no special status for pigeons.     

Systematic errors in pigeons’ memory for event duration: Interaction between training and test delay

Pigeons trained to choose different stimuli following short- and long-duration signals make disproportionately more “short” choices (i.e., “choose-short errors”) following an increase in the retention interval and more “choose-long errors” following a decrease in this delay. The present experiment provided a systematic investigation of how these selective errors depend on the relationship between the training delay and the test delay. Pigeons were first trained with a 0-sec delay between the signal (2- or 8-sec food presentations) and the choice stimuli (red- and blue-lit keys). On subsequent test trials with 5- and 10-sec delays, choose-short errors predominated. Next, the birds were trained with a constant 10-sec delay and then tested with shorter or longer delays on some trials. The birds now responded accurately and without selective errors at the 10-sec training delay, but made choose-long errors at shorter delays and choose-short errors at longer delays. Finally, the birds were trained with a constant 20-sec delay and then tested with shorter and longer delays. Choose-long errors again appeared at shorter test delays, choose-short errors at longer test delays, and no differential errors at the 20-sec training delay. The selectivity of these errors generally increased with the absolute difference between the training and test delay. Theoretical implications of these results are discussed.     

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₋.     

Intradimensional vs. extradimensional transfer in the discriminative learning of goldfish and pigeons

Evidence of better intradimensional than extradimensional transfer was sought in naive goldfish trained under free-operant single-stimulus conditions (Experiment I), sophisticated pigeons trained under free-operant single-stimulus conditions (Experiment II), sophisticated pigeons trained under discrete-trials choice conditions (Experiment III), and naive pigeons trained under discrete-trials choice conditions (Experiment IV). The results provide no support for attention theory.     

常用逻辑门芯片测试装置研究与设计

结合数字电路相关课程的改革,针对数字电路中常用的74/54系列逻辑门芯片,研究并设计了一种基于单片机最小系统的常用逻辑门芯片测试装置。该装置为电子技术相关理论和实践教学提供了快速、直观、稳定的测试方式,提高了实验室芯片检测的效率与准确率,同时也提高了理论与实验课程的教学效果。     

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.     

Spatial matching and nonmatching in male and female Wistar rats: Effects of delay-interval duration

Male and female Wistar rats were trained in a delayed matching-to-position procedure in which one of the two levers (sample) was presented. Pressing this lever resulted in its retraction and began a delay interval of random variable duration, which terminated with the occurrence of the first nose poke in the pellet retrieval unit after the delay interval had expired. Both levers were then inserted into the chamber, and food became available when the subject pressed the lever that had previously been pressed (matching response). When the subject failed to make a matching response, time out (5 sec) was presented. In the next experimental condition, nonmatching was reinforced. Males and females required an equal number of trials to attain 80% accuracy during three consecutive sessions under matching and nonmatching conditions. Response accuracy decreased as the delay interval increased, during both conditions. Differences between the sexes were not observed, suggesting that memory functions in male and female rats may only differ when other behavioral differences between the sexes are allowed to interfere with the assessment of memory functioning.     

Effects of sample duration,retention interval,and passage of time in the test on pigeons’ matching-to-sample performance

Four pigeons served as subjects in an experiment using the go/no-go delayed matching-to-sample paradigm. The go/no-go method was used because it permits the experimenter to track the time course of discriminative performance throughout the test period, unlike the conventional choice matching procedure. It was found that discriminative test performance increased with longer sample durations; performance decreased with longer retention intervals and also as time passed in the test period. The rate of forgetting was virtually the same when either the retention interval was lengthened or time elapsed in the test. These findings support a modified trace theory, which proposes that the sample stimulus trace decays at a constant rate from the point of sample offset, and that the decaying memory trace is repeatedly compared with the prevailing test stimulus as time passes in the test period.     

Interference of delayed matching to sample in pigeons: Effects of interpolation at different periods within a trial and stimulus similarity

Delayed matching-to-sample performance by pigeons was interfered with by displaying a monochromatic annulus around the center (sample) pecking key. The wavelength of the annulus and its point of interpolation within a trial were varied to determine possible differential effects on matching accuracy. Experiment 1 showed that delayed matching was most disrupted when the interference stimulus (570 nm, 630 nm, or achromatic white) appeared during the delay interval of a trial. Little if any disruption occurred when the interference stimulus was present during the sample and choice periods. The spectral relationship between the chromatic interference stimuli (570 and 630 nm) and the sample stimuli (570 and 630 nm) did not consistently influence the degree to which matching accuracy was affected in any interpolation condition. Experiment 2 found a similar pattern of within-trial effects when the interference stimulus was simply a change from a white achromatic annulus to a chromatic one. This finding indicates that illumination changes, such as the popular houselight variation, are not necessary to produce interference in delayed matching to sample. Even with illumination held constant, however, performance was not differentially sensitive to the similarity between interference and sample stimulus wavelengths. It is suggested that other experiments showing similarity effects in interference of delayed matching to sample were conducted in such a way that subjects confused the interfering stimuli with the samples.