The P600 in Implicit Artificial Grammar Learning

The suitability of the artificial grammar learning (AGL) paradigm to capture relevant aspects of the acquisition of linguistic structures has been empirically tested in a number of EEG studies. Some have shown a syntax‐related P600 component, but it has not been ruled out that the AGL P600 effect is a response to surface features (e.g., subsequence familiarity) rather than the underlying syntax structure. Therefore, in this study, we controlled for the surface characteristics of the test sequences (associative chunk strength) and recorded the EEG before (baseline preference classification) and after (preference and grammaticality classification) exposure to a grammar. After exposure, a typical, centroparietal P600 effect was elicited by grammatical violations and not by unfamiliar subsequences, suggesting that the AGL P600 effect signals a response to structural irregularities. Moreover, preference and grammaticality classification showed a qualitatively similar ERP profile, strengthening the idea that the implicit structural mere‐exposure paradigm in combination with preference classification is a suitable alternative to the traditional grammaticality classification test.     

Does stimulus appearance affect learning?

We examined the learning process with 3 sets of stimuli that have identical symbolic structure but differ in appearance (meaningless letter strings, arrangements of geometric shapes, and sequences of cities). One hypothesis is that the learning process aims to encode symbolic regularity in the same way, largely regardless of appearance. Another is that different types of stimuli bias the learning process to operate in different ways. Using the experimental paradigm of artificial grammar learning, we provided a preliminary test of these hypotheses. In Experiments 1 and 2 we measured performance in terms of grammaticality and found no difference across the 3 sets of stimuli. In Experiment 3 we analyzed performance in terms of both grammaticality and chunk strength. Again we found no differences in performance. Our tentative conclusion is that the learning process aims to encode symbolic regularity independent of stimulus appearance.     

Comparison and contrast in perceptual categorization

People categorized pairs of perceptual stimuli that varied in both category membership and pairwise similarity. Experiments 1 and 2 showed categorization of 1 color of a pair to be reliably contrasted from that of the other. This similarity-based contrast effect occurred only when the context stimulus was relevant for the categorization of the target (Experiment 3). The effect was not simply owing to perceptual color contrast (Experiment 4), and it extended to pictures from common semantic categories (Experiment 5). Results were consistent with a sign-and-magnitude version of N. Stewart and G. D. A. Brown's (2005) similarity-dissimilarity generalized context model, in which categorization is affected by both similarity to and difference from target categories. The data are also modeled with criterion setting theory (M. Treisman & T. C. Williams, 1984), in which the decision criterion is systematically shifted toward the mean of the current stimuli.     

Hierarchical forms processing in adults and children

Two experiments examined child and adult processing of hierarchical stimuli composed of geometric forms. Adults (ages 18-23 years) and children (ages 7-10 years) performed a forced-choice task gauging similarity between visual stimuli consisting of large geometric objects (global level) composed of small geometric objects (local level). The stimuli spatial arrangement was manipulated to assess child and adult reaction times and predisposition toward local or global form categorization under two distinct trial conditions, with varied density of the local forms comprising the global forms. In Experiment 1, children and adults were presented with common, simple geometric shape hierarchical forms composed of ovals and rectangles. In Experiment 2, adults were presented with hierarchical forms composed of the simple geometric shapes, ovals and rectangles, and additional novel complex geometric shapes, “posts” and “arches.” Results show a clear increase of global processing bias across the age ranges of the individuals in the study, with children at 10 years performing similarly to adults on the simple stimuli. In addition, adults presented with the novel complex geometric shapes showed a significant reduction in global processing bias, indicating that form novelty and complexity lead to additional attention to local features in categorization tasks.     

The magic spell of language: linguistic categories and their perceptual consequences

Language is a tool that directs attention to different aspects of reality. Using participants from the same linguistic community, the authors demonstrate in 4 studies that metasemantic features of linguistic categories influence basic perceptual processes. More specifically, the hypothesis that abstract versus concrete language leads to a more global versus local perceptual focus was supported across 4 experiments, in which participants used (Experiment 1) or were primed either supraliminally (Experiments 2 and 3) or subliminally (Experiment 4) with abstract (adjectives) or concrete (verbs) terms. Participants were shown to display a global versus specific perceptual focus (Experiments 1 and 4), more versus less inclusiveness of categorization (Experiments 2 and 3), and incorporation of more rather than less contextual information (Experiment 3). The implications of this new perspective toward the language-perception interface are discussed in the context of the general linguistic relativity debate.     

Want to block earworms from conscious awareness?B(u)y gum!

In a recent article, Jamieson and Mewhort (2009) proposed a novel account of artificial grammar learning (AGL), which is based on a multitrace model of episodic memory, the Minerva 2 model. According to this account, test performance in AGL is based on an assessment of global similarity of the test strings to the memory traces of the training strings. In this article, simulation studies are presented, showing for three different AGL experiments that the predictions of the Minerva 2 model strikingly deviate from participants' performance. It is argued that participants' test performance is not generally based on general similarity.     

Evidence for self-organized sentence processing: digging-in effects

Dynamical, self-organizing models of sentence processing predict "digging-in" effects: The more committed the parser becomes to a wrong syntactic choice, the harder it is to reanalyze. Experiment 1 replicates previous grammaticality judgment studies (F. Ferreira & J. M. Henderson, 1991b, 1993), revealing a deleterious effect of lengthening the ambiguous region of a garden-path sentence. The authors interpret this result as a digging-in effect. Experiment 2 finds a corresponding effect on reading times. Experiment 3 finds that making 2 wrong attachments is worse than making 1. Non-self-organizing models require multiple stipulations to predict both kinds of effects. The authors show that, under an appropriately formulated self-organizing account, both results stem from self-reinforcement of node and link activations, a feature that is needed independently. An implemented model is given.     

Crossed categorization in common ingroup contexts

In three experiments, the authors tested the hypothesis that a common ingroup context would moderate evaluations of crossed category targets. In Experiment 1, the typical additive pattern of evaluation across artificial crossed category groups became a social inclusion pattern in a common ingroup context. In Experiment 2, the authors manipulated the importance of real crossed category targets. When the crossed groups were of low importance, the effects of imposing a common ingroup replicated those observed in Experiment 1. For important crossed groups, however, the additive pattern remained. In Experiment 3, the authors measured perceived importance of the crossed groups to social identity prior to introducing a common ingroup context. The effects of a common categorization on evaluations were again moderated by perceived importance. These findings are discussed in the context of integrating crossed categorization and common ingroup identity models of multiple categorization.     

Metamorphosis: Essence, appearance, and behavior in the categorization of natural kinds

The transformation paradigm (Rips, 1989) was used to contrast causal homeostasis and strict essentialist beliefs about biological kinds. Participants read scenarios describing animals that changed their appearance and behavior through either accidental mutation or developmental maturation and then rated the animals on the basis of similarity, typicality, and category membership both before and after the change. Experiment 1 in the present study replicated the dissociation of typicality and categorization reported by Rips (1989) but also revealed systematic individual differences in categorization. With typicality and membership ratings collected between participants, however, Experiment 2 found no evidence for the dissociation and few essentialist responders. In Experiment 3, excluding information about offspring led most participants to categorize on the basis of appearance and behavior alone. However, with offspring information included and with questioning focused on the change of kind, essentialist categorization was still surprisingly rare. We conclude that strict essentialist categorization in the transformation task is relatively rare and highly task dependent, and that categorization is more commonly based on causal homeostasis.     

Dissociations between categorization and similarity judgments as a result of learning feature distributions

A dissociation between categorization and similarity was found by Rips (1989). In one experiment, Rips found that a stimulus halfway between a pizza and a quarter was categorized as a pizza but was rated as more similar to a quarter. Smith and Sloman (1994) discussed these results in terms of the role of necessary and characteristic features. In two experiments, participants had to learn to categorize novel artificial shapes composed of a nonsalient necessary feature combined with a salient characteristic feature. Participants categorized stimuli on the basis of a necessary feature, whereas their similarity judgments relied on characteristic features. The role of deep (essential) features in dissociations is considered. Results are discussed in terms of the differences between requirements of categorization and similarity judgments.     

Forming contextual categories in infancy

The role of context in categorization was examined in four experiments with 3-month-olds. In all experiments infants learned to kick their feet to activate a mobile on 3 successive days. Infants were trained with a different mobile exemplar during each daily session. Categorization of a physically dissimilar novel object (Butterfly) was assessed 1 to 14 days later. In Experiments 1A and 1B, infants were trained and tested in a highly distinctive context. They included Butterfly in the mobile category after 1 and 7, but not after 14, days (Experiment 1A). This latter result was due to a categorization failure because infants did respond to another novel exemplar of the original training series after 14 days (Experiment 1B). In Experiment 2A, infants who were passively exposed to Butterfly for 3 minutes in the distinctive context at the end of category training responded to Butterfly 1 day later when it was encountered “out of context.” This result was also obtained in Experiment 2B when the distinctive context was present only during the final training session. Taken together, these findings demonstrate that categorization of a novel object is influenced by the context present when the object is initially encountered and by previous encounters with that object in the category context. Clearly, infants are capable of contextual categorization very early in the first year of life.     

What's behind different kinds of kinds: effects of statistical density on learning and representation of categories

This research examined how differences in category structure affect category learning and category representation across points of development. The authors specifically focused on category density--or the proportion of category-relevant variance to the total variance. Results of Experiments 1-3 showed a clear dissociation between dense and sparse categories: Whereas dense categories were readily learned without supervision, learning of sparse categories required supervision. There were also developmental differences in how statistical density affected category representation. Although children represented both dense and sparse categories on the basis of the overall similarity (Experiment 4A), adults represented dense categories on the basis of similarity and represented sparse categories on the basis of the inclusion rule (Experiment 4B). The results support the notion that statistical structure interacts with the learning regime in their effects on category learning. In addition, these results elucidate important developmental differences in how categories are represented, which presents interesting challenges for theories of categorization.     

The conscious, the unconscious, and familiarity

This article examines the role of subjective familiarity in the implicit and explicit learning of artificial grammars. Experiment 1 found that objective measures of similarity (including fragment frequency and repetition structure) predicted ratings of familiarity, that familiarity ratings predicted grammaticality judgments, and that the extremity of familiarity ratings predicted confidence. Familiarity was further shown to predict judgments in the absence of confidence, hence contributing to above-chance guessing. Experiment 2 found that confidence developed as participants refined their knowledge of the distribution of familiarity and that differences in familiarity could be exploited prior to confidence developing. Experiment 3 found that familiarity was consciously exploited to make grammaticality judgments including those made without confidence and that familiarity could in some instances influence participants' grammaticality judgments apparently without their awareness. All 3 experiments found that knowledge distinct from familiarity was derived only under deliberate learning conditions. The results provide decisive evidence that familiarity is the essential source of knowledge in artificial grammar learning while also supporting a dual-process model of implicit and explicit learning.     

Arousal, processing, and risk taking: consequences of intergroup anger

Intergroup emotions theory (IET) posits that when social categorization is salient, individuals feel the same emotions as others who share their group membership. Extensive research supporting this proposition has relied heavily on self-reports of group-based emotions. In three experiments, the authors provide converging evidence that group-based anger has subtle and less explicitly controlled consequences for information processing, using measures that do not rely on self-reported emotional experience. Specifically, the authors show that intergroup anger involves arousal (Experiment 1), reduces systematic processing of persuasive messages (Experiment 2), is moderated by group identification (Experiment 2, posttest), and compared to intergroup fear, increases risk taking (Experiment 3). These findings provide converging evidence that consistent with IET, emotions triggered by social categorization have psychologically consequential effects and are not evident solely in self-reports.     

Causal status as a determinant of feature centrality

One of the major problems in categorization research is the lack of systematic ways of constraining feature weights. We propose one method of operationalizing feature centrality, a causal status hypothesis which states that a cause feature is judged to be more central than its effect feature in categorization. In Experiment 1, participants learned a novel category with three characteristic features that were causally related into a single causal chain and judged the likelihood that new objects belong to the category. Likelihood ratings for items missing the most fundamental cause were lower than those for items missing the intermediate cause, which in turn were lower than those for items missing the terminal effect. The causal status effect was also obtained in goodness-of-exemplar judgments (Experiment 2) and in free-sorting tasks (Experiment 3), but it was weaker in similarity judgments than in categorization judgments (Experiment 4). Experiment 5 shows that the size of the causal status effect is moderated by plausibility of causal relations, and Experiment 6 shows that effect features can be useful in retrieving information about unknown causes. We discuss the scope of the causal status effect and its implications for categorization research.     

The relativity of linguistic intuition: The effect of repetition on grammaticality judgments

Three experiments were performed to show the relativity of linguistic intuition in grammaticality judgments. In Experiment 1, 12 students judged the relative grammaticality of isolated sentences twice, receiving a repetition treatment between the two judgments. During the repetition phase, they were exposed to a repeated presentation of sentences. The findings show that the repetition treatment makes a judgment criterion more stringent for both grammatical and ungrammatical sentences. In Experiment 2, a release-from-the-proactive-inhibition paradigm was used. Twelve students first judged the grammaticality of the isolated sentences, then received the repetition treatment, and finally, made a second judgment for the sentences embedded in context. No change in judgment criterion was found for the second judgment. Judgments of the ungrammatical sentences, when embedded in context, were found to be more lenient. In Experiment 3, 12 students judged sentences embedded in context. No change in judgment criterion was found. These findings are interpreted as suggesting that linguistic intuitions as revealed in grammaticality judgments are not absolute but relative in that they are easily influenced by repetition and other variables, such as embedded context.     

Considering multiple criteria for social categorization can reduce intergroup bias

Two experiments tested the notion that considering multiple criteria for social categorization can reduce intergroup bias. In both experiments, participants were required to consider alternative ways in which people could be classified, other than an initially salient intergroup dichotomy. In Experiment 1, the authors found that generating alternative social classifications that were unrelated to an initial target dichotomy reduced intergroup bias compared to a control condition. In Experiment 2, this effect was replicated and the authors found that unrelated, but not related, categorizations were necessary to reduce bias. This article adds support to the view that increasing categorical complexity is a useful tool in bias reduction. These findings are discussed in the context of a developing model of multiple categorization effects.     

Unsupervised categorization and category learning.

When people categorize a set of items in a certain way they often change their perceptions for these items so that they become more compatible with the learned categorization. In two experiments we examined whether such changes are extensive enough to change the unsupervised categorization for the items-that is, the categorization of the items that is considered more intuitive or natural without any learning. In Experiment 1 we directly employed an unsupervised categorization task; in Experiment 2 we collected similarity ratings for the items and inferred unsupervised categorizations using Pothos and Chater's (2002) model of unsupervised categorization. The unsupervised categorization for the items changed to resemble more the learned one when this was specified by the suppression of a stimulus dimension (both experiments), but less so when it was almost specified by the suppression of a stimulus dimension (Experiment 1, nonsignificant trend in Experiment 2). By contrast, no changes in the unsupervised categorization were observed when participants were taught a classification that was specified by a more fine tuning of the relative salience of the two dimensions.     

选择性注意对听觉内隐学习的影响

内隐学习被认为是人类无意识、无目的获得复杂规则的自动化过程。已有研究表明, 在人工语法学习范式下, 视觉内隐学习的发生需要选择性注意。为了考察选择性注意对内隐学习的影响是否具有通道特异性, 本研究以90名大学生为被试, 以人工语法为学习任务, 采用双耳分听技术, 在听觉通道同时呈现具有不同规则的字母序列和数字序列, 考查被试在听觉刺激下对注意序列和未注意序列构成规则的习得情况。结果发现：只有选择注意的序列规则被习得, 未选择注意的序列规则未能被习得。研究表明：在人工语法学习范式下, 只有选择注意的刺激维度能够发生内隐学习。选择性注意对内隐学习的影响具有跨通道的适用性, 不仅适用于视觉刺激, 也同样适用于听觉刺激。     

Knowledge applied to new domains: The unconscious succeeds where the conscious fails

A common view holds that consciousness is needed for knowledge acquired in one domain to be applied in a novel domain. We present evidence for the opposite; where the transfer of knowledge is achieved only in the absence of conscious awareness. Knowledge of artificial grammars was examined where training and testing occurred in different vocabularies or modalities. In all conditions grammaticality judgments attributed to random selection showed above-chance accuracy (60%), while those attributed to conscious decisions did not. Participants also rated each string’s familiarity and performed a perceptual task assessing fluency. Familiarity was predicted by repetition structure and was thus related to grammaticality. Fluency, though increasing familiarity, was unrelated to grammaticality. While familiarity predicted all judgments only those attributed to random selection showed a significant additional contribution of grammaticality, deriving primarily from chunk novelty. In knowledge transfer, as in visual perception (Marcel, 1993), the unconscious may outperform the conscious.