The knowledge acquired during artificial grammar learning: Testing the predictions of two connectionist models

An artificial grammar learning experiment is reported which investigated whether three types of information are learned during this kind of task: information about the positions of single letters, about fragments of training strings, and about entire training strings. Results indicate that participants primarily learned information about string fragments and, to a lesser extent, information about positions of letters. Two connectionist models, an autoassociator and a simple recurrent network (SRN), were tested on their ability to account for these results. In the autoassociator simulations, similarity of test items to entire training items had a large effect, which was at variance with the experimental results. The results of the SRN simulations almost perfectly matched the experimental ones. Received: 22 September 1998 / Accepted: 22 February 1999     

Facilitation of source discrimination in the novelty effect

It has been demonstrated experimentally that recognition of novel items is more accurate than recognition of previously familiarized items. Tulving and Kroll (1995) proposed that this effect is due to novelty detectors in the brain giving processing priority to novel information. Recently, Dobbins et al. (1998) suggested that the effect is due to source discrimination problems. In the present two experiments attempts were made to facilitate source discrimination by having different orienting tasks and materials in the familiarization and in the critical presentations. Degree of familiarization was manipulated by varying number of presentations one, two or three times. The results in Experiment 1 showed that the novelty effect increased linearly as a function of presentations in the familiarization phase. In the second experiment the difference between familiar and novel items was even more pronounced. Enactment at encoding was added as a manipulation during familiarization. The results of Experiment 2 showed that the novelty effect did increase linearly for items with nonenacted encoding (in which the familiarization and the critical phase were more similar) but not for enacted encoding. All subjects reported experiencing source discrimination difficulties in both experiments despite the measures taken to diminish them. It seems safe to conclude that source discrimination difficulties are a part of the novelty effect.     

Individual differences in emotional expression discrimination are associated with emotion label production in toddlers

It is possible that the visual discrimination of emotion categories and emotion word vocabulary develop via common emotion-specific processes. In contrast, it is possible that they develop with vocabulary development more generally. This study contrasts these two possibilities. Twenty-three 26-month-olds participated in a visual perceptual discrimination task involving emotional facial expressions. After familiarization to a 100% happy face, toddlers were tested for their visual preference for a novel sad face in a side-by-side presentation paired with the familiar happy face. Parental report was used to quantify production of emotion words and vocabulary generally. Visual preference for the novel emotion (sad) in the discrimination task correlated with emotion word vocabulary size but not with overall vocabulary size.     

Two ways of learning associations

How people learn chunks or associations between adjacent items in sequences was modelled. Two previously successful models of how people learn artificial grammars were contrasted: the CCN, a network version of the competitive chunker of Servan‐Schreiber and Anderson [J. Exp. Psychol.: Learn. Mem. Cogn. 16 (1990) 592], which produces local and compositionally‐structured chunk representations acquired incrementally; and the simple recurrent network (SRN) of Elman [Cogn. Sci. 14 (1990) 179], which acquires distributed representations through error correction. The models' susceptibility to two types of interference was determined: prediction conflicts, in which a given letter can predict two other letters that appear next with an unequal frequency; and retroactive interference, in which the prediction made by a letter changes in the second half of training. The predictions of the models were determined by exploring parameter space and seeing howdensely different regions of the space of possible experimental outcomes were populated by model outcomes. For both types of interference, human data fell squarely in regions characteristic of CCN performance but not characteristic of SRN performance.     

The role of the physical context in supporting young children's use of spatiotemporal organization in recall

Four experiments were conducted to investigate the role of the physical context in supporting 3‐ to 5‐year‐olds' use of spatiotemporal organization in recall. Children were familiarized with several target items and their corresponding landmarks arranged along a path in a model park. After familiarization, an experimenter removed the target items from the park. In Experiment 1, 3‐ and 4‐year‐olds recalled the missing items with the park either in view or out of view. When the park model was in view, 4‐ year‐olds used the order of the items along the path to structure their recall. In Experiment 2, 4‐ and 5‐year‐olds recalled the missing items with the landmarks arranged either in the same order as in familiarization or in a new order. Children used the order of landmarks along the path at test to structure their recall, even though the order of landmarks changed from familiarization to test. Experiment 3 was identical to Experiment 2, except that the path was removed from the park. Five‐year‐olds used the order of landmarks along the path at test to structure their recall when the order of landmarks remained the same from familiarization to test, but had much more difficulty doing so when the order of landmarks changed from familiarization to test. Using a more difficult task, Experiment 4 revealed that spatiotemporal organization was positively related to amount recalled. Together, these findings suggest that the structure of the physical environment plays an important role in supporting young children's use of spatiotemporal organization in recall.     

Learning non-local dependencies

This paper addresses the nature of the temporary storage buffer used in implicit or statistical learning. Kuhn and Dienes [Kuhn, G., and Dienes, Z. (2005). Implicit learning of nonlocal musical rules: implicitly learning more than chunks. Journal of Experimental Psychology-Learning Memory and Cognition, 31(6) 1417-1432] showed that people could implicitly learn a musical rule that was solely based on non-local dependencies. These results seriously challenge models of implicit learning that assume knowledge merely takes the form of linking adjacent elements (chunking). We compare two models that use a buffer to allow learning of long distance dependencies, the Simple Recurrent Network (SRN) and the memory buffer model. We argue that these models - as models of the mind - should not be evaluated simply by fitting them to human data but by determining the characteristic behaviour of each model. Simulations showed for the first time that the SRN could rapidly learn non-local dependencies. However, the characteristic performance of the memory buffer model rather than SRN more closely matched how people came to like different musical structures. We conclude that the SRN is more powerful than previous demonstrations have shown, but it's flexible learned buffer does not explain people's implicit learning (at least, the affective learning of musical structures) as well as fixed memory buffer models do.     

Brain dynamics of word familiarization in 20-month-olds: effects of productive vocabulary size

The present study investigated the brain mechanisms involved during young children's receptive familiarization with new words, and whether the dynamics of these mechanisms are related to the child's productive vocabulary size. To this end, we recorded event-related potentials (ERPs) from 20-month-old children in a pseudoword repetition task. Results revealed distinct patterns of repetition effects for children with large and small productive vocabularies. High producers showed evidence of recognizing the novel words already after three presentations, while the low producers needed five presentations to display a recognition effect. The familiarization process was manifested in the modulations of two components, the N200-400 and a later fronto-central component, which appeared to increase in amplitude until a certain level of encoding was reached and then decrease with further repetition. These findings suggest a relation between the onset of the productive vocabulary spurt and the rate of receptive word familiarization.     

Infants' discrimination of photographs of faces following redundant presentations

Infants' discrimination of photographs of faces, as indicated by fixation toward novel targets, was the criterion used to evaluate familiarization conditions designed to facilitate the exercise of selective attention. Groups of 19- and 23-week-old infants were shown either pictures of different faces of the same sex, differing poses of the same face, or repeated exposures of the face that served as a test stimulus. The older infants demonstrated differential attention to novel over familiar stimuli during subsequent recognition tests, and an examination of their responsiveness during familiarization presentations indicated differing trends of looking activity.     

初中词汇理解能力量表的编制

应用项目反应理论为初中各年级编制了词汇理解能力的测验,其中包含了１４３个多项选择的词汇项目,经过反复预测和大规模的正式测试,证关了这三个测验的量表拟全于２ＰＬ模型,项目特征曲线拟合度良好的项目占全体项目数９０％以上,能力的一维性也得以确认,经等值化后,各年级的区分度均值分别为０．６１（初一）,０．５９（初二）,０．５５（初三）难度均值分别为－１．６１,－１．３０,－０．５６。     

Two are better than one: comparison influences infants' visual recognition memory

Despite a large literature on infants’ memory for visually presented stimuli, the processes underlying visual memory are not well understood. Two studies with 4-month-olds (N = 60) examined the effects of providing opportunities for comparison of items on infants’ memory for those items. Experiment 1 revealed that 4-month-olds failed to show evidence of memory for an item presented during familiarization in a standard task (i.e., when only one item was presented during familiarization). In Experiment 2, infants showed robust memory for one of two different items presented during familiarization. Thus, infants’ memory for the distinctive features of individual items was enhanced when they could compare items.     

远距离规则的内隐学习使用了何种记忆存储器：来自神经网络模拟的证据

关于远距离规则的知识是如何被内隐学习的,研究尚未得出结论。该研究通过采用和人类被试相同的实验材料和程序,考察了简单循环网络模型（SRN）对两种汉语声调远距离规则——倒映和逆行规则的内隐学习。结果发现：1.在广泛的参数范围上,SRN能够学会倒映和逆行规则,表明模型的记忆缓冲器可以模拟人类远距离规则的内隐学习;2.SRN对倒映规则的学习比对逆行规则的学习更好,表明在功能上远距离规则的内隐学习可能优先使用了先进先出的记忆存储器及信息加工模式。该研究为探究远距离规则内隐学习的机制提供了新的证据和视角。     

Rapid learning of syllable classes from a perceptually continuous speech stream

To learn a language, speakers must learn its words and rules from fluent speech; in particular, they must learn dependencies among linguistic classes. We show that when familiarized with a short artificial, subliminally bracketed stream, participants can learn relations about the structure of its words, which specify the classes of syllables occurring in first and last word positions. By studying the effect of familiarization length, we compared the general predictions of associative theories of learning and those of models postulating separate mechanisms for quickly extracting the word structure and for tracking the syllable distribution in the stream. As predicted by the dual-mechanism model, the preference for structurally correct items was negatively correlated with the familiarization length. This result is difficult to explain by purely associative schemes; an extensive set of neural network simulations confirmed this difficulty. Still, we show that powerful statistical computations operating on the stream are available to our participants, as they are sensitive to co-occurrence statistics among non-adjacent syllables. We suggest that different learning mechanisms analyze speech on-line: A rapid mechanism extracting structural information about the stream, and a slower mechanism detecting statistical regularities among the items occurring in it.     

Odor discrimination and recognition memory as a

The role of olfactory familiarization in short-term recognition of odors was investigated. Subjects were asked to make qualitative similarity judgments regarding either identical or dissimilar odors delivered in pairs. Except for control groups, subjects got familiarized with either the first (target) or the second (distractor) or both odors from a pair. Groups also differed according to the number of familiarization sessions—one, two, or three—taking place prior to the discrimination judgments. There was no significant influence of familiarization on correct recognition scores for pairs of identical odors. The most salient finding was a marked decrease of false alarms as a function of the number of familiarization sessions, which evidenced a positive effect of familiarization on discrimination for pairs of dissimilar odors. These judgments were not dependent on an intensity criterion. False alarms did not vary according to whether subjects had been familiarized with the target or the distractor or both odors from a pair. A positive correlation found between discrimination performances and the number of odors correctly remembered as being presented during familiarization suggested that familiarization resulted in long-term storing of memory traces for familiarized odors. Since familiarization was effective despite conditions unfavorable to the use of semantic encoding, the results argue in favor of a predominantly perceptual encoding of odors in the investigated task.     

Lure similarity affects visual episodic recognition: Detailed tests of a noisy exemplar model

Summed-similarity models of visual episodic recognition memory successfully predict the variation in false alarm rates across different test items. With data averaged across subjects, Kahana and Sekuler demonstrated that subjects' performance appears to change along with the mean similarity among study items; with high interstimulus similarity, subjects were less likely to commit false alarms to similar lures. We examined this effect in detail by systematically varying the coordinates of study and test items along a critical stimulus dimension and measuring memory performance at each point. To reduce uncontrolled variance associated with individual differences in vision, the coordinates of study and test items were scaled according to each subject's discrimination threshold. Fitting each of four summed-similarity models to the individual subjects' data demonstrated a clear superiority for models that take account of interitem similarity on a trialwise basis.     

Delayed recognition memory for orientation by human infants

The familiarization/novelty preference paradigm was employed to study the effect of a delay (between the end of the familiarization phase and the beginning of the test phase) on discrimination of the orientation of square-wave gratings by 2- and 3-month-old human infants. Three stimulus pairs were studied: horizontal-vertical, non-mirror-image obliques, and mirror-image obliques. The data indicate that the members of the oblique-oblique stimulus pairs are confused in memory to a greater extent than the members of the horizontal-vertical stimulus pair. These findings are consistent with P.C. Bomba's (1984, Journal of Experimental Child Psychology, 37, 609-636) recent report that infants respond to the orientation of a visual stimulus in a categorical-like manner.     

Sequential Presentation Protects Working Memory From Catastrophic Interference

Neural network models of memory are notorious for catastrophic interference: Old items are forgotten as new items are memorized (French, 1999; McCloskey & Cohen, 1989). While working memory (WM) in human adults shows severe capacity limitations, these capacity limitations do not reflect neural network style catastrophic interference. However, our ability to quickly apprehend the numerosity of small sets of objects (i.e., subitizing) does show catastrophic capacity limitations, and this subitizing capacity and WM might reflect a common capacity. Accordingly, computational investigations (Knops, Piazza, Sengupta, Eger & Melcher, 2014; Sengupta, Surampudi & Melcher, 2014) suggest that mutual inhibition among neurons can explain both kinds of capacity limitations as well as why our ability to estimate the numerosity of larger sets is limited according to a Weber ratio signature. Based on simulations with a saliency map-like network and mathematical proofs, we provide three results. First, mutual inhibition among neurons leads to catastrophic interference when items are presented simultaneously. The network can remember a limited number of items, but when more items are presented, the network forgets all of them. Second, if memory items are presented sequentially rather than simultaneously, the network remembers the most recent items rather than forgetting all of them. Hence, the tendency in WM tasks to sequentially attend even to simultaneously presented items might not only reflect attentional limitations, but also an adaptive strategy to avoid catastrophic interference. Third, the mean activation level in the network can be used to estimate the number of items in small sets, but it does not accurately reflect the number of items in larger sets. Rather, we suggest that the Weber ratio signature of large number discrimination emerges naturally from the interaction between the limited precision of a numeric estimation system and a multiplicative gain control mechanism.     

Cognitive control factors in speech perception at 11 months

The development of speech perception during the 1st year reflects increasing attunement to native language features, but the mechanisms underlying this development are not completely understood. One previous study linked reductions in nonnative speech discrimination to performance on nonlinguistic tasks, whereas other studies have shown associations between speech perception and vocabulary growth. The present study examined relationships among these abilities in 11-month-old infants using a conditioned head-turn test of native and nonnative speech sound discrimination, nonlinguistic object-retrieval tasks requiring attention and inhibitory control, and the MacArthur-Bates Communicative Development Inventory (L. Fenson et al., 1993). Native speech discrimination was positively linked to receptive vocabulary size but not to the cognitive control tasks, whereas nonnative speech discrimination was negatively linked to cognitive control scores but not to vocabulary size. Speech discrimination, vocabulary size, and cognitive control scores were not associated with more general cognitive measures. These results suggest specific relationships between domain-general inhibitory control processes and the ability to ignore variation in speech that is irrelevant to the native language and between the development of native language speech perception and vocabulary.     

Accommodating variability in voice and foreign accent: flexibility of early word representations

In six experiments with English‐learning infants, we examined the effects of variability in voice and foreign accent on word recognition. We found that 9‐month‐old infants successfully recognized words when two native English talkers with dissimilar voices produced test and familiarization items ( Experiment 1 ). When the domain of variability was shifted to include variability in voice as well as in accent, 13‐, but not 9‐month‐olds, recognized a word produced across talkers when only one had a Spanish accent ( Experiments 2 and 3 ). Nine‐month‐olds accommodated some variability in accent by recognizing words when the same Spanish‐accented talker produced familiarization and test items ( Experiment 4 ). However, 13‐, but not 9‐month‐olds, could do so when test and familiarization items were produced by two distinct Spanish‐accented talkers ( Experiments 5 and 6 ). These findings suggest that, although monolingual 9‐month‐olds have abstract phonological representations, these representations may not be flexible enough to accommodate the modifications found in foreign‐accented speech.     

The novelty effect: support for the Novelty-Encoding Hypothesis

In two experiments, we examined the "Novelty-Encoding Hypothesis" proposed by Tulving and Kroll (1995), suggesting that the encoding of online information into long-term memory is influenced by its novelty and that novelty increases recognition performance. In Phase 1 (familiarization phase), subjects participated in a standard memory experiment in which different types of materials (verbs and nouns) were studied under different encoding conditions (enactment and non-enactment) and were tested by an expected recognition test. In Phase 2 (critical phase), subjects evaluated the materials (both familiar materials which were encoded earlier in Phase 1, and novel materials which were not presented earlier in Phase 1) in a frequency judgment task and were given an unexpected recognition test. The results of both experiments showed that novel items were recognized better than familiar items. This result held true for both hit rates - false alarms and hit rates. The novelty effect was observed for different subjects (Swedish and Japanese), different materials (verbs and nouns; high frequency and low frequency), and different types of encoding in Phase 1 (enactment and non-enactment). These findings provide support for the "Novelty-Encoding Hypothesis" stating that the effect is based on the encoding of target items at the time of the critical study (Phase 2). A comparison between the present experiments and the Tulving and Kroll (1995), Dobbins, Kroll, Yonelinas & Liu (1998) and Greene (1999) studies suggests that the novelty effect is more pronounced under incidental encoding than under intentional encoding.     

Normal aging increases discriminal dispersion in visuospatial short-term memory

Computational models of cognitive aging propose that age-related decrements in cognitive performance, including short-term memory (STM), result from less distinct stimulus representations. When applied to visual STM, these models predict higher discriminal dispersion (L. L. Thurstone, 1927, Psychophysical analysis, The American Journal of Psychology, 38, 368-389.) in older adults than in younger adults. To test this prediction, we used a change-detection paradigm for visuospatial locations, with different levels of cognitive load (one, three, or five items) and retention interval (100 or 1,000 ms). Adult age differences were not reliable at Load 1, but were substantial at Loads 3 and 5. Effects of retention time did not differ across age groups, suggesting that age-related differences originated mainly from early processing stages. Applying a mixture model to the data revealed age-related increases in discriminal dispersion and decreases in asymptotic discrimination performance (indexing STM capacity). We concluded that age-related declines in discriminal dispersion, in addition to increasing capacity limitations, impair visual STM performance with advancing adult age. (PsycINFO Database Record (c) 2012 APA, all rights reserved).