Episodic representations support early semantic learning: evidence from midazolam induced amnesia

Current controversy exists regarding the role of episodic representations in the formation of long-term semantic memories. Using the drug midazolam to induce temporary amnesia we tested participants' memories for newly learned facts in a semantic cue condition or an episodic and semantic cue condition. Following midazolam administration, memory performance was superior in the episodic and semantic condition, suggesting early semantic learning is supported by episodic representations.     

Lexical competition and the acquisition of novel words

Three experiments examined the involvement of newly learnt words in lexical competition. Adult participants were familiarized with novel nonsense sequences that overlapped strongly with existing words (e.g. cathedruke, derived from cathedral) through repeated presentation in a phoneme-monitoring task. Experiment 1 looked at the immediate effects of exposure to these sequences, with participants showing familiarity with the form of the novel sequences in a two-alternative forced choice task. The effect of this exposure on lexical competition was examined by presenting the existing words (e.g. cathedral) in a lexical decision task. The immediate effect of the exposure was facilitatory, suggesting that the novel words had activated the representation of the closest real word rather than developing their own lexical representations. In Experiment 2, inhibitory lexical competition effects emerged over the course of 5 days for offset-diverging (e.g. cathedruke-cathedral) but not onset-diverging (e.g. yothedral-cathedral) novel words. Experiment 3 disentangled the roles of time and level-of-exposure in the lexicalization process and assessed the generality of the observed lexical inhibition using pause detection. A single, concentrated exposure session was used, which resulted in good recognition performance soon after. Lexicalization effects were absent immediately after exposure but emerged 1 week later, despite no intervening exposure to the novel items. These results suggest that integrating a novel word into the mental lexicon can be an extended process: phonological information is learnt swiftly, but full integration with existing items develops at a slower rate.     

Vocabulary teaching strategies and conceptual representations of words in L2 in children: Evidence with novice learners

A controversial issue in bilingual research is whether in the early stages of L2 learning, access to the conceptual system involves mediation of L1 lexical representations [Kroll, J. F., & Stewart, E. (1994). Category interference in translation and picture naming: Evidence for asymmetric connections between bilingual memory representations. Journal of Memory and Language, 33, 149-174] or a direct route from the L2 word [Altarriba, J., & Mathis, K. M. (1997). Conceptual and lexical development in second language acquisition. Journal of Memory and Language, 36, 550-568; Finkbeiner, M., & Nicol, J. (2003). Semantic category effects in second language word learning. Applied Psycholinguistics, 24, 369-383]. The main goal of this paper is to study, in a child population, whether the creation of conceptual representations for L2 words is possible, even after only one session of learning of the L2 vocabulary. Furthermore, we do so by examining the efficacy of two different L2 learning methods: L2-L1 association learning vs. L2-picture association learning. A translation recognition task was employed to test whether there was a difference between a semantically related pair and an unrelated pair across conditions (i.e., a semantic interference effect). Results showed a significant semantic interference effect—a conceptual effect—in children after just one vocabulary learning session. Importantly, the L2-picture method produced a greater semantic interference effect than the L2-L1 method. The implications of these findings for models of bilingual memory are examined.     

Hemispheric asymmetries in semantic processing: evidence from false memories for ambiguous words

We used fMRI to investigate competition during language production in two word production tasks: object naming and color naming of achromatic line drawings. Generally, fMRI activation was higher for color naming. The line drawings were followed by a word (the distractor word) that referred to either the object, a related object, or an unrelated object. The effect of the distractor word on the BOLD response was qualitatively different for the two tasks. The activation pattern suggests two different kinds of competition during lexical retrieval: (1) Task-relevant responses (e.g., red in color naming) compete with task-irrelevant responses (i.e., the object’s name). This competition effect was dominant in prefrontal cortex. (2) Multiple task-relevant responses (i.e., target word and distractor word) compete for selection. This competition effect was dominant in ventral temporal cortex. This study provides further evidence for the distinct roles of frontal and temporal cortex in language production, while highlighting the effects of competition, albeit from different sources, in both regions.     

Producing and recognizing words with two pronunciation variants: evidence from novel schwa words

This study examined the lexical representations and psycholinguistic mechanisms underlying the production and recognition of novel words with two pronunciation variants in French. Participants first learned novel schwa words (e.g., /??nyk/), which varied in their alternating status (i.e., whether these words were learned with one or two variants) and, for alternating words, in the frequency of their variants. They were then tested in picture-naming (free or induced) and recognition memory tasks (i.e., deciding whether spoken items were learned during the experiment or not). Results for free naming show an influence of variant frequency on responses, more frequent variants being produced more often. Moreover, our data show an effect of the alternating status of the novel words on naming latencies, with longer latencies for alternating than for nonalternating novel words. These induced naming results suggest that both variants are stored as lexical entries and compete during the lexeme selection process. Results for recognition show an effect of variant frequency on reaction times and no effect of variant type (i.e., schwa versus reduced variant). Taken together, our findings suggest that participants both comprehend and produce novel French schwa words using two lexical representations, one for each variant.     

Why children learn color and size words so differently: evidence from adults' learning of artificial terms.

An adult simulation study examined why children's learning of color and size terms follow different developmental patterns, one in which word comprehension precedes success in nonlinguistic matching tasks versus one in which matching precedes word comprehension. In 4 experiments, adults learned artificial labels for values on novel dimensions. Training mimicked that characteristic for children learning either color words or size words. The results suggest that the learning trajectories arise from the different frames in which different dimensions are trained: Using a comparison (size-like) training regimen helps learners pick out the relevant dimension, and using a categorization (color-like) training regimen helps the learner correctly comprehend and produce dimension terms. The results indicate that the training regimen, not the meanings of the terms or the specific dimensions, determines the pattern of learning.     

Implicit word learning benefits from semantic richness: electrophysiological and behavioral evidence

Words differ considerably in the amount of associated semantic information. Despite the crucial role of meaning in language, it is still unclear whether and how this variability modulates language learning. Here, we provide initial evidence demonstrating that implicit learning in repetition priming is influenced by the amount of semantic features associated with a given word. Electroencephalographic recordings were obtained while participants performed a visual lexical decision task; the complete stimulus set was repeated once. Repetition priming effects on performance accuracy and the N400 component of the event-related brain potential were enhanced for words with many semantic features. These findings suggest a novel and important impact of the richness of semantic representations on learning and plasticity within the lexical-conceptual system; they are discussed in their relevance for assumptions concerning basic mechanisms underlying word learning.     

Phonological sensitivity and the acquisition of new words in children

Two studies are reported which aimed to examine the relationship between phonological sensitivity and the acquisition of new words that systematically differed in the familiarity of their sound structures. In the first study measures of phonological sensitivity, phonological short-term memory, vocabulary, and nonverbal ability were administered to forty-one 5-year-old children. Phonological sensitivity was related to the paired-associate learning of phonologically unfamiliar words, but not to the learning of familiar words. In the second study a group of 14 nonreading 5-year-old children received phonological sensitivity training. A control group was trained in semantic categorization. After the training, the phonological sensitivity group did perform better on measures of letter knowledge and phonological sensitivity (rhyme and first-sound categorization) and appeared to learn phonologically unfamiliar words more easily. The findings of both studies suggest that phonological sensitivity can support the acquisition of novel words.     

Lexical and semantic influences on item and order memory in immediate serial recognition: evidence from a novel task

Previous studies have reported that, in contrast to the effect on immediate serial recall, lexical/semantic factors have little effect on immediate serial recognition. This has been taken as evidence that linguistic knowledge contributes to verbal short-term memory in a redintegrative process at recall. Contrary to this view, we found that lexicality, frequency, and imageability all influenced matching span. The standard matching span task, requiring changes in item order to be detected, was less susceptible to lexical/semantic factors than was a novel task involving the detection of phoneme order and hence item identity changes. Therefore, in both immediate recognition and immediate serial recall, lexical/semantic knowledge makes a greater contribution to item identity than to item order memory. Task sensitivity, and not the absence of overt recall, may have underpinned previous failures to show effects of these variables in immediate recognition. We also compared matching span for pure and unpredictable mixed lists of words and nonwords. Lexicality had a larger impact on immediate recognition for pure than for mixed lists, in line with findings for immediate serial recall. List composition affected the detection of phoneme but not item order changes in matching span; similarly, in recall, mixed lists produce more frequent word phoneme migrations but not migrations of entire items. These results point to strong similarities between immediate serial recall and recognition. Lexical/semantic knowledge may contribute to phonological stability in both tasks.     

Lexical information drives perceptual learning of distorted speech: evidence from the comprehension of noise-vocoded sentences

Speech comprehension is resistant to acoustic distortion in the input, reflecting listeners' ability to adjust perceptual processes to match the speech input. For noise-vocoded sentences, a manipulation that removes spectral detail from speech, listeners' reporting improved from near 0% to 70% correct over 30 sentences (Experiment 1). Learning was enhanced if listeners heard distorted sentences while they knew the identity of the undistorted target (Experiments 2 and 3). Learning was absent when listeners were trained with nonword sentences (Experiments 4 and 5), although the meaning of the training sentences did not affect learning (Experiment 5). Perceptual learning of noise-vocoded speech depends on higher level information, consistent with top-down, lexically driven learning. Similar processes may facilitate comprehension of speech in an unfamiliar accent or following cochlear implantation.     

Semantics and semantic errors: implicit access to semantic information from words and nonwords in deep dyslexia

In this paper we describe dissociations of implicit versus explicit access to semantic information in a patient with deep dyslexia. This acquired reading disorder is characterized by the production of morphological (e.g., SLEEP read as SLEEPING) and semantic errors (e.g., HEART read as BLOOD) and consequently provides a potential window into the operation of both aspects of the language system. The deep dyslexic patient in this study (JO) demonstrated implicit semantic access to items in a number of tasks despite the fact that she was unable to correctly read these items aloud. The findings from this study are consistent with a model of lexical deficits that distinguishes between explicit and implicit access to lexical representations on the basis of inhibitory processes.     

Serial and free recall in children can be improved by training: evidence for the importance of phonological and semantic representations in immediate memory tasks

Children were assigned to three groups given training on unfamiliar words--phoneme-awareness training, rhyme training, and vocabulary training--and an untrained control group. Before and after training, we assessed the children's performance on serial- and free-recall tasks with these words, as well as their ability to define the words, manipulate phonemes in them, and generate rhymes for them. We found that phoneme-awareness training improved serial recall substantially and improved free recall to a lesser extent. In contrast, vocabulary training produced a substantial increase in free recall and a lesser increase in serial recall. These effects on recall were specific and did not generalize to untrained words. Rhyme training produced increases in rhyming skills but no increase in either serial or free recall. We argue that serial and free recall depend on common memory mechanisms, but serial recall relies more on phonological codes and free recall relies more on semantic codes.     

Numerosity discrimination in infants: evidence for two systems of representations

Two experiments investigated numerosity discrimination in 6-month-old infants, comparing their performance on both large numbers (4 vs. 8 elements) and small numbers (2 vs. 4 elements) with both total filled area and total contour length controlled for. These studies provide the first direct comparison between discrimination of small and large numbers in infants with the same methodology, the same type of stimuli, and the same continuous variable controls. Results showed that infants succeeded in discriminating 4 from 8 elements but failed to discriminate 2 from 4 elements, providing evidence for the existence of two systems of number representations in infancy.     

Comprehension of argument structure and semantic roles: evidence from English-learning children and the forced-choice pointing paradigm

Research using the intermodal preferential looking paradigm (IPLP) has consistently shown that English-learning children aged 2 can associate transitive argument structure with causal events. However, studies using the same methodology investigating 2-year-old children's knowledge of the conjoined agent intransitive and semantic role assignment have reported inconsistent findings. The aim of the present study was to establish at what age English-learning children have verb-general knowledge of both transitive and intransitive argument structure using a new method: the forced-choice pointing paradigm. The results suggest that young 2-year-olds can associate transitive structures with causal (or externally caused) events and can use transitive structure to assign agent and patient roles correctly. However, the children were unable to associate the conjoined agent intransitive with noncausal events until aged 3;4. The results confirm the pattern from previous IPLP studies and indicate that children may develop the ability to comprehend different aspects of argument structure at different ages. The implications for theories of language acquisition and the nature of the language acquisition mechanism are discussed.     

The effect of age of acquisition in visual word processing: further evidence for the semantic hypothesis

The authors investigated whether the meaning of visually presented words is activated faster for early-acquired words than for late-acquired words. They addressed the issue using the semantic Simon paradigm. In this paradigm, participants are instructed to decide whether a stimulus word is printed in uppercase or lowercase letters. However, they have to respond with a verbal label ("living" or "nonliving") that is either congruent with the meaning of the word (e.g., saying "living" to the stimulus DOG) or incongruent (e.g., saying "nonliving" to the stimulus dog). Results showed a significant congruency effect that was stronger for early-acquired words than for late-acquired words. The authors conclude that the age of acquisition is an important variable in the activation of the meaning of visually presented words.     

Episodic and semantic knowledge in emotional self-report: evidence for two judgment processes

Three studies involving 3 participant samples (Ns = 39, 55, and 53) tested the hypothesis that people retrieve episodic emotion knowledge when reporting on their emotions over short (e.g., last few hours) time frames, but that they retrieve semantic emotion knowledge when reporting on their emotions over long (e.g., last few months) time frames. Support for 2 distinct judgment strategies was based on judgment latencies (Studies 1 and 2) and priming paradigms (Studies 2 and 3). The authors suggest that self-reports of emotion over short versus long time frames assess qualitatively different sources of self-knowledge.     

The effects of late acquisition of L2 and the consequences of immigration on L1 for semantic and morpho-syntactic language aspects

It has been hypothesized that some aspects of a second language (L2) might be learned easier than others if a language is learned late. On the other hand, non-use might result in a loss of language skills in one's native, i.e. one's first language (L1) (language attrition). To study which, if any, aspects of language are affected by either late acquisition or non-use, long-term German immigrants to the US and English native speakers who are long-term immigrants to Germany as well as two additional control groups of native German speakers were tested with an auditory semantic and morpho-syntactic priming paradigm. German adjectives correctly or incorrectly inflected for gender and semantically associated or not associated with the target noun served as primes. Participants made a lexical decision on the target word. All groups of native German speakers gained from semantically and morpho-syntactically congruent primes. Evidence for language attrition was neither found for semantic nor morpho-syntactic priming effects in the German immigrants. In contrast, English native speakers did not gain from a morpho-syntactic congruent prime, whereas semantic priming effects were similar as for the remaining groups. The present data suggest that the full acquisition of at least some syntactic functions may be restricted to limited periods in life while semantic and morpho-syntactic functions seem to be relatively inured to loss due to non-use.     

The semantic organization of the animal category: evidence from semantic verbal fluency and network theory

Semantic memory is the subsystem of human memory that stores knowledge of concepts or meanings, as opposed to life-specific experiences. How humans organize semantic information remains poorly understood. In an effort to better understand this issue, we conducted a verbal fluency experiment on 200 participants with the aim of inferring and representing the conceptual storage structure of the natural category of animals as a network. This was done by formulating a statistical framework for co-occurring concepts that aims to infer significant concept-concept associations and represent them as a graph. The resulting network was analyzed and enriched by means of a missing links recovery criterion based on modularity. Both network models were compared to a thresholded co-occurrence approach. They were evaluated using a random subset of verbal fluency tests and comparing the network outcomes (linked pairs are clustering transitions and disconnected pairs are switching transitions) to the outcomes of two expert human raters. Results show that the network models proposed in this study overcome a thresholded co-occurrence approach, and their outcomes are in high agreement with human evaluations. Finally, the interplay between conceptual structure and retrieval mechanisms is discussed.