Maze-arm length affects a choice criterion in the radial-arm maze

Male rats were tested in a 12-arm radial maze with 6 arms that were standard in length and 6 arms that were half the standard length. As previously reported by Brown (1990), revisits to short arms were more likely than revisits to long arms. Two explanations of this effect of mazearm length on choice accuracy were experimentally contrasted. The first attributes the effect to diminished discriminability of visited and unvisited arms when the arms are short. The second attributes the effect to a relatively lax choice criterion being applied to short arms. An analysis of the microstructure of choices, applying the logic of signal detection theory, provided evidence for the latter explanation.     

Spatial memory and the performance of rats and pigeons in the radial-arm maze

The resource-distribution hypothesis states that the ability of an animal to remember the spatial location of past events is related to the typical distribution of food resources for the species. It appears to predict that Norway rats would perform better than domestic pigeons in tasks requiring spatial event memory. Pigeons, tested in an eight-arm radial maze, exhibited no more than half of the memory capacity observed in rats in the same apparatus and may not have used spatial memory at all. The results were interpreted as supporting the hypothesis.     

Foraging on the radial-arm maze: Effects of altering the reward at a target location

Thirsty rats were trained to collect small water rewards from the end of each arm of an eight-arm radial maze. During these training trials and subsequent testing trials, the subjects were allowed to choose a maximum of eight arms. “Preference” for a target maze location was studied by noting when, in the sequence of eight choices, the target was selected. During testing, when one maze location was consistently devoid of water, rats decreased their preference for this arm over trials (Experiment 1). Similarly, rats that learned a saccharin-lithium association demonstrated lower preferences for a maze location that consistently held the conditioned saccharin solution. This was true for animals that received saccharin-lithium conditioning on the maze (Experiment 3A) and for animals conditioned to saccharin in a separate context (Experiment 3B). An increase in preference for a target maze location consistently containing a sweet chocolate milk solution was observed in animals that were water- and food-deprived (Experiment 2). These studies demonstrate that animals will modify their responses toward (preferences for) maze locations that predictably contain an altered reward.     

A “random-walk” simulation model of multiple-pattern learning in a radial-arm maze

Wathen and Roberts (1994) reported rather surprising results of a radial maze study that on any interpretation requires postulation of previously unsuspected high-level cognitive processes in rats. In each of four arms of the eight-arm radial maze, a different serial pattern unfolded over trials; for example, in one of the arms reward and nonreward alternated over successive trials. On each trial, rats came to track successfully four different patterns simultaneously. The authors suggested that rats tracked the pattern by using some form of trial-number strategy; that is, the trial number indicated which arms contained the better rewards. This strategy could involve a hypothesis, considered unlikely by some, that rats are capable of keeping track of as many as eight successive events—as, for example, by counting. A simulation model that embodies a specific form of the trial-number hypothesis is described here, and the results of the simulation correlate remarkably well with the observed data. In addition, the model makes four separate predictions that are supported by Wathen and Roberts’s data and that seem beyond the scope of other available theories.     

Social effects on spatial choice in the radial arm maze

Social memory was investigated in the context of a spatial working memory task. Pairs of rats were tested in an eight-arm radial maze. Under most conditions, there was a tendency to choose maze locations that had been visited earlier by the other rat. The possibility that this tendency is produced by common preferences for particular maze locations was ruled out. An opposite tendency to avoid visits to locations that had been visited earlier during the trial by another rat was found only when the maze location contained two pellets (rather than an undepletable supply), the rats’ ability to see each other in the maze was restricted to the central arena, and the maze location had been previously visited by the focal rat. The amount of food available in maze locations did not otherwise modulate social influences on spatial choice. The results indicate that memory for a rat’s own previous choices is combined with memory for the choices made by another rat.     

The effect of maze structure upon the performance of a multiple-goal task

Learning & Behavior - The ability of rats to find food in three kinds of mazes (radial, parallel, antiradial) was studied. Each maze had eight goalboxes. All goals were baited at the beginning...     

Two sources of proactive interference in spatial working memory: Multiple effects of repeated trials on radial maze performance by rats

Rats were trained in 8- and 12-arm radial mazes. Each trial began with a study phase (forced choices of 4 arms). The trial ended after a 2-h delay in a test phase consisting of free choices among 8 arms; choices of the 4 arms not yet visited were correct (rewarded). Proactive interference (PI) was induced by an interference phase that occurred on some days 2 or 3 h prior to the study phase. In the PI-repetition condition, the interference phase consisted of forced choices of the 8 arms that were later presented in the study and test phases; in the PI-nonrepetition condition, the interference consisted of forced choices of the 4 arms that were correct during the test phase. Test-phase performance was most accurate in the No PI (single-trial) condition and least accurate in the PI-repetition condition. A second experiment showed that repetitions per se were not responsible for the PI; when the interference phase consisted only of choices of the same 4 arms later presented in the study phase, no PI was observed. These findings suggest two sources of PI. One source, measured by the difference between No PI and PI-nonrepetition conditions, appears to be a difficulty in discriminating the temporal order of visits to arms in the interference and study phases. The other source of PI, measured by the difference between the nonrepetition and repetition conditions, remains to be identified; some possibilities are discussed.     

Partial reinforcement effects on learning and extinction of place preferences in the water maze

In two experiments, two groups of rats were trained in a navigation task according to either a continuous or a partial schedule of reinforcement. In Experiment 1, animals that were given continuous reinforcement extinguished the spatial response of approaching the goal location more readily than animals given partial reinforcement—a partial reinforcement extinction effect. In Experiment 2, after partially or continuously reinforced training, animals were trained in a new task that made use of the same reinforcer according to a continuous reinforcement schedule. Animals initially given partial reinforcement performed better in the novel task than did rats initially given continuous reinforcement. These results replicate, in the spatial domain, well-known partial reinforcement phenomena typically observed in the context of Pavlovian and instrumental conditioning, suggesting that similar principles govern spatial and associative learning. The results reported support the notion that salience modulation processes play a key role in determining partial reinforcement effects.     

管路长度对箕斗定重称载液压系统动态和静态性能的影响

针对王石凹煤矿定重称载系统液压元件和管路受损严重,且系统存在响应滞后和称重不准确等问题。本文采用AMESim方法建立了定重称载液压系统的仿真模型,分析了液压管路长度对箕斗定重称载液压系统的响应速度、准确性及系统刚度等动态和静态指标的影响,结果表明:液压管道的内径恒定时,系统的超调量、调整时间、固有频率、相对误差和刚度随管道长度的增大而减小,阻尼比随管道长度的增大而增大。建议系统设计时直接测量载荷增量,并根据管道长度对系统误差的影响进行质量补偿。     

Intratrial proactive interference in rats’ serial alternation performance in the radial maze

Rats acquired a serial alternation task in an eight-arm radial maze that was partitioned into four pairs of arms. Each pair was associated with a different distal stimulus. Rats were initially forced to the left or right arm in each pair (the study segment) before being exposed to both arms in each pair (the free-choice or test segment). Only the previously blocked arm of each pair remained baited. Following initial training, proactive interference (PI) was induced by presenting rats with a forced-choice (prestudy) segment containing arm positions opposite those in the subsequent study segment. Such trials generated poorer free-choice accuracy than did trials without a prestudy segment. Forcing rats to both arms in the pair in a prestudy segment produced only transient PI. A slight improvement in rats’ free-choice performance was obtained by forcing them to the same arm position, but only when the test segment was delayed by 30 min. Increasing the interval between the prestudy and study segments from 2 to 30 min eliminated PI, but only when free-choice testing was delayed by 2 min rather than by 30 min. These results suggest that intratrial PI in this preparation was primarily due to confusion about which arm position in each pair had been visited during the last forced-choice segment.     

The effects of morphology and word length on the reading of Hebrew nominals

This article investigated the effects of twospecific Hebrew nominal word structures andword length, on the latency and accuracy ofgrade school children's reading ofwords. For this study, three-, four- and five-letterwords of the feminine nominalderivative structure and the feminine nominalinflectional structure, at three differentgrade levels, were used. The study alsodifferentiated between an additional vocalizedconsonant and the addition of a vowel letter.The participants, 150 native monolingual Hebrewspeakers in grades two, four and six, wereasked to read vocalized nouns. The paperreports and analyzes the differences in thereading of the two morphological structures andword lengths to draw conclusions about theireffects on reading performance. The resultsindicated that inflections took longer to readand elicited more correct responses thanderivations. For derivations with theprogression of grade level, latency becomesshorter and the number of correct responsesincreases. For inflections with the progressionof grade level, latency becomes longer but thenumber of correct responses increases. With theaddition of a consonant at all grade levels,latency becomes longer. For accuracy, therewere differential results for the differentword lengths in the different grades. With theaddition of a vowel letter, accuracy increasedin all the grade levels. Latency, for the twoword lengths, showed differential results inthe different grades. A hypothesis on readingdevelopment is suggested based on the language-specificcharacteristics of Hebrew morphologyand the double vowel system of Hebrew.     

内插管长度对排气抗性消声器性能的影响

提高消声器的声学性能,通常会导致空气动力性能的增大,因此要对消声器的综合性能进行评价。利用COMSOL Multiphysics和FLUENT商业软件,对某汽车排气抗性消声器的综合性能进行研究,分别对其在具有4种不同内插管长度组合情况下的声场和流场进行数值模拟,获得消声器的声压分布特性、传递损失及压力损失,并分析和研究了内插管长度对消声器声学性能和空气动力学性能的影响。模拟结果表明,随着内插管长度的增加,消声器的传递损失在低频段明显提高,且消声器的压力损失有所下降,从而汽车排气抗性消声器的综合性能得到了提高。     

The effects of Greek affiliation on academic performance

We use a difference-in-differences approach to estimate the effects of Greek affiliation on academic performance. There are strong negative effects in some periods but smaller effects in others: fraternity affiliation hurts performance by 0.32 standard deviations in the Freshman Spring; sorority affiliation hurts performance by 0.22 standard deviations in Spring semesters after Freshman year. We estimate both ceteris-paribus effects and non-ceteris-paribus effects which allow Greek affiliation to influence course choice behavior. We account for censoring of grades and show ignoring censoring leads to attenuation bias. We also document heterogeneity in treatment effects by student preparation and organization social status.     

Variations in radial maze performance under different levels of food and water deprivation

Four groups of rats were tested on an eight-arm radial maze under a free-choice procedure. The subjects were maintained at either 80% or 100% of their preexperimental free-feeding weights through restricted access to either food or water. Water-deprived subjects received water in the maze; food-deprived subjects received food. Water-deprived subjects learned the task faster than food-deprived subjects. The four groups developed different response patterns. These were measured by themean transition size, the average angular distance (in 45° units) between consecutively chosen arms. Rats foraging for food and water developed different search strategies, with water-deprived subjects exhibiting lower mean transition sizes. When the subjects were given three consecutive trials, 2 min apart, choice accuracy declined across trials, although performance on the last two trials improved across days. The groups’ mean transition sizes remained different, and were constant over trials and days. Thus, the test procedures differentially affected choice accuracy and response patterning.     

The effects of new science curricula on student performance

This study summarizes the results of a quantitative synthesis of the retrievable primary research dealing with the effects of new science curricula on student performance. This study synthesizes the results of 105 experimental studies involving more than 45,000 students and utilizes the quantitative synthesis perspective to research integration known as meta-analysis (Glass, 1976). A total of 27 different new science curricula involving one or more measures of student performance are included in this meta-analysis. Data were collected for 18 a priori selected student performance measures. The results of this meta-analysis reveal definite positive patterns of student performance in new science curricula. Across all new science curricula analyzed, students exposed to new science curricula performed better than students in traditional courses in general achievement, analytic skills, process skills, and related skills (reading, mathematics, social studies and communication), as well as developing a more positive attitude toward science. On a composite basis, the average student in new science curricula exceeded the performance of 63% of the students in traditional science courses.     

Central-place foraging by rats on the radial maze: The effects of patch size,food distribution,and travel time

Rats foraged on a four-arm radial maze with one, two, three, and four food items (0.65.g pieces of cheese) placed on different arms (patches) of the maze. In two experiments, the hypothesis was tested that rats should carry food to the center of the maze more often when a patch contains one food item than when it contains multiple food items. Support for this prediction was found when the tendency to carry initial items encountered in patches was compared among the different sized patches. However, a further observation failed to support the hypothesis: Food carrying declined from first to last item encountered in multiple-item patches with clustered food items. Experiment 1 revealed that food carrying was reduced when travel time was increased by barriers placed at arm entrances. Both Experiments 1 and 2 indicated that the tendency for rats to carry food to the center of the radial maze increased as the distance of food encountered on an arm increased from the center. In both experiments, some rats dealt with the problem of multiple items by resorting to multiple-item loading, and some rats carried food items from the end of an arm to a point on the arm nearer the center for consumption.     

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.     

The effects of contingent feedback on perceived control and performance

The purpose of this study was to examine the impact on students’ performance of three contingent feedback strategies used by teachers. Contigency means that the feedback strongly corresponds with task behaviour that can be controlled by the students. Elementary school students (N=296) received individualized feedback about their performance during a series of five lessons. Within this contingent feedback structure, three strategies were applied which were assumed to enhance the perceived controllability of the task situation: (1) enhancing the perceptibility of the contingency between feedback and task behavior; (2) explicit reference to effort as part of the feedback, and (3) setting of goals. As predicted, the three contingent feedback strategies had a significant positive effect on perceived controllability, and led to better task performance.     

The effects of strong irrelevant thirst on food-rewarded instrumental performance

In Experiment I, rats received one food rewarded trial per day in a runway. One group received all its trials under hunger (Group H); the second group received a random half of its trials under hunger and the other half of its trials under hunger plus thirst (Group H-HT). Group H-HT ultimately ran slower on HT trials than on H trials. In Experiment II, the effects of shifting from H to HT and vice versa were examined in a five-phase design. In general, rats run under H ran faster than rats run under HT, and shifts from H to HT produced rapid decreases in speed, while shifts from HT to H produced extremely slow increases in speed. The results of both experiments were interpreted as indicating that the reward value of food is greater under H than under HT and that the manipulation H vs. HT may be viewed as theoretically similar to manipulation of reward magnitude.