Control of performance by short-term memory in honeybees

Individual honeybees foraging at a laboratory window were trained with a correction method to choose between blue and yellow targets, one of which contained sucrose solution. There were two trials on each visit, with the locus of the sucrose predictable only on the second. Animals differentially rewarded on Trial 2 for choosing the rewarded color of Trial 1, for choosing the alternative color, or for choosing the target in the rewarded position of Trial 1 independently of its color, all showed a small but persistent preference for the rewarded color, with no significant preference for the rewarded position. When the positions of the colored targets were the same on Trial 2 as on Trial 1 (color and position confounded), there was a more substantial but equally persistent preference on Trial 2 for the rewarded color-position of Trial 1, whether the animals were differentially rewarded for perseveration or for alternation. The results provide further evidence of unlearned control of performance by short-term memory in honeybees but no indication of learned control.     

Effects of signaled retention intervals on pigeon short-term memory

In three delayed matching-to-sample experiments, pigeons were given distinctive stimuli that were either correlated or uncorrelated with the scheduled retention intervals. Experiment 1 employed a single-key, go/no-go matching procedure with colors as the sample and test stimuli; lines of differing orientations signaled short or long delays for one group, whereas the lines and the delays were uncorrelated for the other group. The function relating discriminative test performance to delay length was steeper in the correlated group than in the uncorrelated group. In addition, the line orientation stimuli controlled differential rates of sample responding in the correlated group, but not in the uncorrelated group. In Experiment 2, subjects extensively trained with correlated line orientations were exposed to reversed cues on probe trials. Miscuing decreased discriminative test responding at the short delay, but enhanced it at the long delay. As in the correlated group of the first experiment, rates of sample keypecking were higher in the presence of the “short” time tag than in the presence of the ”long” time tag. Experiment 3 used a three-key choice-matching procedure and a within-subjects design, and equated reinforcement rate at the short and long delays. When auditory stimuli were correlated with delay length, the function relating choice accuracy to delay was steeper than when the stimuli and the delays were uncorrelated. The consistent effects of signaled retention intervals on memory performance may be understood in terms of differential attention to the sample stimuli.     

Attention problems,phonological short-term memory,and visuospatial short-term memory: Differential effects on near- and long-term scholastic achievement

The current study examined individual differences in children's phonological and visuospatial short-term memory as potential mediators of the relationship among attention problems and near- and long-term scholastic achievement. Nested structural equation models revealed that teacher-reported attention problems were associated negatively with composite scholastic achievement (reading, math, language), both initially and at 4-year follow-up in an ethnically diverse sample of children (N = 317). Much of this influence, however, was attenuated by phonological short-term memory's contribution to near-term achievement and visuospatial short-term memory's contribution to long-term achievement. Domain-specific reading and math models showed similar results with some exceptions. In all models, measured intelligence made no contribution to later achievement beyond its initial influence on early achievement. The results contribute to our understanding of the mechanisms associated with individual differences in children's scholastic achievement, and have potential implications for identifying early predictors of children at risk for academic failure, and developing remedial programs targeting phonological and visuospatial short-term memory deficits in children with attention problems.     

Effects of intratrial stimulus change on fixed-interval performance: The roles of clock and memory processes

In two experiments, pigeons were exposed to differentially cued training trials of fixed interval (FI) 30 and 60 sec. In addition, shift trials were presented in which the cue associated with one FI value was presented for a prearranged duration at trial onset, followed by offset of that cue and presentation of the other cue. Response-contingent reinforcement was scheduled during the second cue. During the first shift phase, the FI 30-sec cue was shifted to the FI 60-sec cue; in a second phase, the order of the cue shift was reversed. Inferences about accumulator and memory functions of the internal clock were based upon behavior during both training trials and shift trials. At the end of both shift phases, test-trial FI functions generally superimposed in a manner consistent with accumulator reset on cue shift. Individual differences in clustering of functions were accommodated by variation in reference-memory storage across subjects. This interpretation was tested in Experiment 2 by constraining reference-memory storage on shift trials. These conditions yielded a decrease in between-subject variability and provided data consistent with accumulator reset and control by a single reference-memory value on shift trials.     

Memory priming and trial spacing effects in Pavlovian learning

Conditioning trials that are massed in time produce less conditioning than those that are spaced in time. Four experiments with rat subjects examined whether a recent conditioning trial interferes with conditioning on the next trial by temporarily “priming” information in short-term memory (e.g., Wagner, 1978, 1981). We used appetitive conditioning procedures in which priming trials preceded target trials by 60 sec. When the priming trials were nonreinforced presentations of a conditioned stimulus (CS), the CS had to be the same CS as the one on the target trial to interfere with conditioning. When priming trials were actual CS-unconditioned stimulus (US) pairings, the CS identity did not matter; the US was the event that interfered with conditioning on the next trial. Reinforced trials reduced performance in a way that did not depend on context blocking. The results suggest that CS and US priming effects do contribute to conditioning deficits observed with massed trial procedures. The results are consistent with Wagner’s (1981) “sometimes opponent process,” or SOP, model, although a result that is paradoxical for the model suggests that recent USs may have motivational as well as memory effects.     

US duration and local trial spacing affect autoshaped responding

The acquisition and maintenance of signal-directed pecking was examined in week-old Leg-Horn chicks responding to a keylight stimulus paired with heat. In contrast with previous studies using pigeons with food as the US, both speed of acquisition and asymptotic level of keypecking were a direct function of US duration. Experiment 2 examined responding using a within-subject design to isolate the effects of trial spacing on performance during the immediate trial from the effects on performance during a following trial of fixed length. These comparisons revealed a significant effect of intertriai interval (ITI), with less responding after shorter intervals. The effect of different temporal spacing was apparent in responding on the immediate trial, but not on the following trial. These local ITI effects were better predicted by a recent autoshaping model based on relative waiting time (Jenkins, Barnes, & Barrera, 1981) than by a model based on relative US expectancy (Gibbons & Balsam, 1981). However, neither model predicted the effect of US duration. A reexamination of the US-duration literature suggested that the diversity of previous findings is consistent with the assumption that conditioned responding is an inverted U-shaped function of US duration.     

Reading ability and short-term memory: The role of phonological processing

The aim of the current study was to further explore the connection between verbal short-term recall and phonological processing for two purposes: (a) To investigate the basis of short-term memory deficits for children with reading disability, and (b) To further explore the origin of developmental verbal memory span increases.Using a variety of memory and phonological tasks, reading group comparisons were conducted testing third-grade good readers and poor readers, and developmental changes were studied with pre-kindergarten, first-grade and third-grade children. The main finding was that a strong relationship was observed between efficiency of phonological processes and capacity of verbal memory supporting the hypothesis that reducing phonological processing requirements in verbal short-term memory increases available resources for storage. No such relationship was found between phonological processing and nonverbal memory. This conclusion was supported by two findings: (a) The verbal short-term memory deficits in poor readers significantly correspond with less accurate phonological processing, and (b) Developmental increases in verbal STM are accompanied by more accurate and rapid execution of phonological tasks.     

Stimulus modality and short-term memory in rats

Two experimental paradigms are presented aimed at determining the retention of auditory and visual information over brief delay intervals. First, a conditional delayed matching-to-sample procedure was used in which rats were required to symbolically match the modality of the sample stimulus with one of two comparison stimuli. In the second experiment, subjects were trained and tested using a Konorski-type procedure. Despite the conceptual and procedural differences between the two procedures, subjects in both experiments showed steeper forgetting functions for visual events than for auditory events, while performance levels at 0-sec delay intervals were equivalent for both stimuli. These results, when taken together with related research conducted with pigeons, suggest that content of memory may have important influences on the short-term retention abilities of animal subjects.     

Codes and coding processes in pigeon short-term memory

The delayed matching-to-sample (DMTS) task was used in three experiments to investigate how pigeons code information about sample stimuli. In all experiments, each trial consisted of a signaled presentation of a sample stimulus for a fixed duration followed, after some delay, by the presentation of three comparison stimuli. After incorrect first choices, the bird was allowed a second choice between the remaining two stimuli. It was found, in Experiment 1, that the probability of a second choice error declined with increasing sample duration. This result is consistent with a gradual short-term memory encoding process but not with a simple two-state all-or-none process. In the second experiment, it was found that the distribution of first-choice errors was affected by the particular sample occurring on a trial. This result is inconsistent with a two-stage discrete state memory/attention model based on the assumption that encoding of the sample and attention to the comparison stimuli are both independent all-or-none processes. The third experiment involved symbolic DMTS, in which the sample stimuli varied along a dimension different from that along which the comparison stimuli varied. With increasing delay between sample and comparison stimulus presentations, the pigeons were more likely to confuse test stimuli than to confuse sample stimuli. The results of these experiments lead to the conclusion that pigeon DMTS performance depends on a gradual encoding process in which a representation isomorphic with the test stimuli is generated and maintained.     

Effects of gender role and task content on performance in same-gender dyads: Transactive memory as a potential mediator

This experiment was designed to examine the effects of gender role and task content on performance in learning dyads and to test the potential mediator effect of an intragroup process related to transactive memory. A total of 44 same-gender dyads participated in the study and were asked to collaborate on a stereotypically masculine or feminine task in a laboratory setting. Collective performance and transactive memory were measured. As predicted, the results showed an interaction between group gender and task content on group performance, with male dyads showing poorer performance on a masculine task than female dyads. However, contrary to expectations, this moderation effect was not mediated by transactive memory, which appeared as a simple mediator of the relationship between group gender and performance. The results are discussed in the framework of the social role theory, and implications for future research in small learning groups are proposed.     

Representation strength in pigeon short-term memory: Effect of delay training

An attempt was madeto manipulate the strength of internal stimulus representations by exposing pigeons to brief delays between sample offset and comparison onset in a delayed conditional discrimination. In Experiment 1, pigeons were first trained on delayed conditional discrimination with either short (0.5-sec) delays or no delays. When delays were increased by 2.0 sec, birds trained with a delay performed at a higher level than did birds trained with no delays. In Experiment 2, subjects were first trained on a delayed simple discrimination. Following a circle stimulus, responses to a white key were reinforced; however, following a dot stimulus, responses to the white key were not reinforced. The pigeons were then trained on a delayed conditional discrimination involving hue samples and line-orientation comparisons with differential outcomes. Choice of vertical following red yielded food; choice of horizontal following green yielded no food. Mixed delays were then introduced to birds in Group Delay, whereas birds in the control group received overtraining. When tested on a delayed simple discrimination with hue stimuli (red and green initial stimuli followed by white response stimulus), pigeons in Group Delay tended to perform at a higher level than did birds in the control group (i.e., although the birds in both groups responded more following red than following green, birds in Group Delay did this to a greater extent than did birds in the control group). Thus, experience with delays appears to strengthen stimulus representations established during training.     

Reinforcement expectancy and trial spacing effects in delayed matching-to-sample by pigeons

Four experiments assessed the role of reinforcement expectancies in the trial spacing effect obtained in delayed matching-to-sample by pigeons. In Experiment 1, a differential outcome (DO) group received reinforcement with a probability of 1.0 for correct comparison responses following one sample stimulus and a probability of 0.2 for correct comparison responses following the other sample stimulus. The nondifferential outcome (NDO) group received reinforcement with a probability of 0.6 for correct responses to either stimulus. While matching accuracy was higher for the DO group than for the NDO group, both groups showed an equivalent decline in accuracy as the intertriai interval (ITI) duration was decreased. However, within the DO group, ITI duration affected performance on low-probability-of-reinforcement trials but not on high-probability-of-reinforcement trials. In Experiment 2, delay interval (DI) duration was 5, 10, or 15 sec and accuracy was higher for the DO group than for the NDO group at all DI durations. In addition, accuracy decreased similarly on high- and low-probability-of-reinforcement trials for the DO group as DI was increased. In Experiment 3, all birds were studied under DO conditions and ITI duration was manipulated along with DI duration. At the short DI duration, decreasing ITI duration had a detrimental effect on low-probability-of-reinforcement trials but no effect on high-probability-of-reinforcement trials. At the long DI duration, decreasing ITI duration had detrimental effects on both types of trials. In Experiment 4, unsignaled ITI reinforcers disrupted accuracy when the DI was long and when the ITI was short. The applicability of scalar expectancy theory to these data is discussed.     

Interference and auditory short-term memory in the bottlenosed dolphin

Interference in auditory short-term memory in the bottlenosed dolphin,Tursiops truncatus (Montagu), was studied using a delayed matching-to-sample task. At each trial, one of two sample sounds, chosen randomly, was projected underwater for 4 sec and then, after a variable delay interval, both sounds were presented. A response to the sound matching the initial sample was reinforced. Correct matching was significantly reduced following short intervals between trials in combination with long delays after the sample (proactive interference), or when a near continuous irrelevant sound was inserted into the delay interval (retroactive interference). There was rapid habituation to interference if the irrelevant sound was short in duration relative to the delay interval. For both proactive and retroactive interference, the errors were predominantly responses to the sample sound appropriate to the prior trial rather than to the current trial, indicating that memory for the relative recency of events (temporal memory) was degraded by interference. When interference was deleted or minimized, temporal memory remained nearly perfect over 30-sec delay intervals, the longest tested. The importance of distinguishing between temporal memory and nontemporal, or event, memory in different forms of the delayed matching task was emphasized.     

The impact of metamemory and domain-specific knowledge on memory performance

This paper consists of two major parts. First, research exploring possible interactions between metamemory and domain-specific knowledge in influencing children’s text recall and comprehension is briefly summarized. Overall, the findings indicate that metacognitive knowledge does make a difference even in cases where domain-specific knowledge is rich. Second, a recent experiment conducted in our lab and investigating the generalizability of this conclusion for sort-recall tasks is described in more detail. Third — and fourth-grade soccer experts and novices were first given a comprehensive metamemory questionnaire and then administered a sort-recall tasks using two different picture lists: whereas one list included items from various semantical categories (e.g., animals, clothes), the other list was composed of soccer pictures that could be classified in several categories such as players, kicks, or equipment. The results showed that although domain-specific knowledge had a strong impact on recall of the soccer list, general metacognitive knowledge made an independent contribution, particularly for the group of soccer experts. More specifically, good metamemory positively affected the recall of experts but had no impact on novices’ memory performance.     

Selected short-term memory tests as predictors of reading readiness

Three standardized measures of short-term memory (STM) were compared to determine their relative efficacy in predicting reading achievement for primary grade students (n = 36) over a two-year time period. Regression analyses revealed that not all of the STM tests were significant (p < .05) predictors of reading. Moreover, predictive power varied as a function of the reading skill assessed (e.g., decoding or comprehension) and the grade placement of the student. A letter sequences test was found to be the task most frequently associated with reading performance. A memory-for-sentences task also showed a significant relationship to certain aspects of reading. However, a word sequences test was found not to be predictive of reading achievement. Implications for test selection and remedial planning are discussed. © 1998 John Wiley & Sons, Inc.     

Humor and anxiety: Effects on class test performance

Measures of trait anxiety, state anxiety, and achievement were obtained on a sample of undergraduate students, half of whom received additionaal humorous items in the achievement test. In a regression analysis, the trait anxiety × test version interaction was a significant predictor of achievement. Subsequent analyses revealed a disordinal interaction in which highly anxious students had lower achievement on the humorous test than on the nonhumorous test, and students with low anxiety had higher achievement on the humorous test than did students with high anxiety. The results do not support the popular assumption that humor is a positive factor in reducing high anxiety associated with academic evaluations.     

Effects of reward amount and reward omission on short-term retention

A series of four experiments studied the retention of the response made on a just-preceding trial as a function of the presence, and amount, of food reward given on that trial. Rats were trained to alternate arm choices in a T-maze, and then were tested for alternation with 5- or 30-sec delays between runs. When the subjects had received prior experience with the reward amounts used in testing, larger rewards led to better retention than did small or no rewards. However, when reward omission first occurred during the test phase, it produced more alternation on the following trial than did reward presence. The results suggest that both reward amount and surprisingness determine short-term retention of responses paired with the rewards.     

Effects of stimulus spacing on steady state gradients of inhibitory stimulus control

When the response of pigeons is maintained to a number of stimulus wavelengths, but extinguished to one (S?), the birds peck more rapidly at stimuli near the S? than at more distant stimuli. The present study explores this “dimensional contrast” effect as a function of the number and spacing of test wavelengths. A fixed portion of the wavelength continuum was spanned by 5, 9, 13, or 49 stimuli, which appeared in random sequence behind a standard pecking key. At the end of each 20-sec trial, pecks to test stimuli produced a conditioned reinforcer (sometimes followed by food), while pecks to the S? stimulus produced only darkness. Dimensional contrast “shoulders” developed to test stimuli on either side of the S?; these shoulders were of approximately the same height and wavelength position for all but the 5-stimulus (widely spaced) condition, and were comparable to the original contrast results with 25 stimuli. The results strongly suggest that the extent and locus of contrast shoulders are largely independent of the number and spacing of test stimuli.     

隔离桩间距对基坑开挖引起地铁隧道的位移影响分析

基于杭州市某房建地下室深基坑工程采用隔离桩保护邻近既有地铁隧道的工程案例,采用ABAQUS有限元软件进行数值模拟,建立三维模型对不同隔离桩间距下隧道的位移进行分析。结果表明:基坑开挖最终引起隧道下沉约3.1mm,隧道向靠近基坑方向水平位移约1.7mm,数值模拟计算结果与现场实测数据的相关规律吻合;隔离桩间距越小,基坑开挖引起邻近既有地铁隧道位移越小。