Watching the infant brain learn words: effects of vocabulary size and experience

Previous investigations comparing auditory event-related potentials (ERPs) to words whose meanings infants did or did not comprehend, found bilateral differences in brain activity to known versus unknown words in 13-month-old infants, in contrast with unilateral, left hemisphere, differences in activity in 20-month-old infants. We explore two alternative explanations for these findings. Changes in hemispheric specialization may result from a qualitative shift in the way infants process known words between 13 and 20 months. Alternatively, hemispheric specialization may arise from increased familiarity with the individual words tested. We contrasted these two explanations by measuring ERPs from 20-month-old infants with high and low production scores, for novel words they had just learned. A bilateral distribution of ERP differences was observed in both groups of infants, though the difference was larger in the left hemisphere for the high producers. These findings suggest that word familiarity is an important factor in determining the distribution of brain regions involved in word learning. An emerging left hemispheric specialization may reflect increased efficiency in the manner in which infants process familiar and novel words.     

A statistical estimate of infant and toddler vocabulary size from CDI analysis

For the last 20 years, developmental psychologists have measured the variability in lexical development of infants and toddlers using the MacArthur-Bates Communicative Development Inventories (CDIs) - the most widely used parental report forms for assessing language and communication skills in infants and toddlers. We show that CDI reports can serve as a basis for estimating infants' and toddlers'total vocabulary sizes, beyond serving as a tool for assessing their language development relative to other infants and toddlers. We investigate the link between estimated total vocabulary size and raw CDI scores from a mathematical perspective, using both single developmental trajectories and population data. The method capitalizes on robust regularities, such as the overlap of individual vocabularies observed across infants and toddlers, and takes into account both shared knowledge and idiosyncratic knowledge. This statistical approach enables researchers to approximate the total vocabulary size of an infant or a toddler, based on her raw MacArthur-Bates CDI score. Using the model, we propose new normative data for productive and receptive vocabulary in early childhood, as well as a tabulation that relates individual CDI measures to realistic lexical estimates. The correction required to estimate total vocabulary is non-linear, with a far greater impact at older ages and higher CDI scores. Therefore, we suggest that correlations of developmental indices to language skills should be made to vocabulary size as estimated by the model rather than to raw CDI scores.     

Statistical regularities in vocabulary guide language acquisition in connectionist models and 15-20-month-olds

This research tested the hypothesis that young children's bias to generalize names for solid objects by shape is the product of statistical regularities among nouns in the early productive vocabulary. Data from a 4-layer Hopfield network suggested that the statistical regularities in the early noun vocabulary are strong enough to create a shape bias, and that the shape bias is overgeneralized to nonsolid stimuli. A 2nd simulation suggested that this overgeneralization is due to the dominance of names for shape-based categories in the early noun vocabulary. Two subsequent longitudinal experiments tested whether it is possible to create word learning biases in children. Children 15-20 months old were given intensive naming experiences with 12 noun categories typical of the types of categories children learn to name early. The children developed a precocious shape bias that was overgeneralized to naming nonsolid substances; they also showed accelerated vocabulary development. Children taught an atypical set of nouns or no new nouns did not develop a shape bias and did not show accelerated vocabulary development.     

Reexamining the vocabulary spurt

The authors asked whether there is evidence to support the existence of the vocabulary spurt, an increase in the rate of word learning that is thought to occur during the 2nd year of life. Using longitudinal data from 38 children, they modeled the rate of word learning with two functions, one with an inflection point (logistic), which would indicate a spurt, and one without an inflection point (quadratic). Comparing the fits of these two functions using likelihood ratios, they found that just 5 children had a better logistic fit, which indicated that these children underwent a spurt. The implications for theories of cognitive and language development are considered.     

Relationship between intelligence and vocabulary

This study explored the correlations of scores on the Wechsler Intelligence Scale for Children-III in screening language problems and scores on the three Comprehensive Receptive and Expressive Vocabulary Test subscales. Participants were 243 students ages 6 to 17 years in Grades K-11 who were identified as learning disabled, learning disabled with speech impairment, mentally retarded, and speech impaired. Analysis indicated strong correlations between the two measures, particularly between the CREVT General Vocabulary and WISC-III Verbal IQ (r = .80), WISC-III Verbal Comprehension Index (r =.83), and the Vocabulary subtest (r =.76). These results held across the grades. Supporting earlier studies of relationships of Verbal IQ and Receptive Vocabulary, correlations were lower between participants in Grades K through 2 than those in higher grades on the WISC-III Verbal IQ and the Receptive Vocabulary subtest. An analysis of the accuracy of the WISC-III for classifying students with language problems indicated improvement in classification over chance. These findings suggest that the WISC-III may be an effective screen for language problems.     

Grammatical incongruency and vocabulary types

Four experiments conducted in French were performed to investigate the role of grammatical congruency and vocabulary class on lexical decision times. In Experiment 1, using a double lexical decision, slower reaction times were found for pairs of words that disagreed in gender or number than for congruent pairs. Experiments 2, 3, and 4 tested this effect with a standard priming procedure. The grammatical congruency effect varied according to presentation times (130, 150, or 500 msec) and to vocabulary class of context word (closed or open). Closed-class context words induced stronger grammatical effect than did open-class words. These results suggest that the grammatical link existing between the two words of a pair is more immediately computed when the first one is a closed-class item and argue for a distinct computational role of open- and closed-class words in sentence processing.     

Human simulations of vocabulary learning

The work reported here experimentally investigates a striking generalization about vocabulary acquisition: Noun learning is superior to verb learning in the earliest moments of child language development. The dominant explanation of this phenomenon in the literature invokes differing conceptual requirements for items in these lexical categories: Verbs are cognitively more complex than nouns and so their acquisition must await certain mental developments in the infant. In the present work, we investigate an alternative hypothesis; namely, that it is the information requirements of verb learning, not the conceptual requirements, that crucially determine the acquisition order. Efficient verb learning requires access to structural features of the exposure language and thus cannot take place until a scaffolding of noun knowledge enables the acquisition of clause-level syntax. More generally, we experimentally investigate the hypothesis that vocabulary acquisition takes place via an incremental constraint-satisfaction procedure that bootstraps itself into successively more sophisticated linguistic representations which, in turn, enable new kinds of vocabulary learning. If the experimental subjects were young children, it would be difficult to distinguish between this information-centered hypothesis and the conceptual change hypothesis. Therefore the experimental "learners" are adults. The items to be "acquired" in the experiments were the 24 most frequent nouns and 24 most frequent verbs from a sample of maternal speech to 18-24-month-old infants. The various experiments ask about the kinds of information that will support identification of these words as they occur in mother-to-child discourse. Both the proportion correctly identified and the type of word that is identifiable changes significantly as a function of information type. We discuss these results as consistent with the incremental construction of a highly lexicalized grammar by cognitively and pragmatically sophisticated human infants, but inconsistent with a procedure in which lexical acquisition is independent of and antecedent to syntax acquisition.     

Aging and vocabulary scores: a meta-analysis

Vocabulary scores were examined in a total of 210 articles, containing 324 independent pairings of younger and older adults, from the 1986-2001 issues of Psychology and Aging. The average effect size, favoring the old, was 0.80 SD. Production tests yielded smaller effects (0.68 SD) than multiple-choice tests (0.93 SD). Both age and education were found to be partially independent determinants of performance in production tests; age effects disappeared in multiple-choice tests as soon as education was taken into account. In addition, the Wechsler Adult Intelligence Scale--Revised Vocabulary subtest (D. Wechsler, 1981) was also found to be sensitive to the Flynn effect (J. R. Flynn, 1987; i.e., increasing test scores with advancing birth year). The results question the approach of using age-group equality in vocabulary scores as a check on sample equivalence.     

The long past and short history of the vocabulary of Anglophone psychology

How do particular words come to be part of the vocabulary of Anglophone psychology? The present study sampled 600 words with psychological senses from the Oxford English Dictionary, which not only gives the number of senses for each word but also the date and author for the earliest known occurrence of each sense. Analogous information for the same words was taken from PsycINFO. One can distinguish between words for which their psychological sense is the first to occur in the history of the written language (primary psychological words) and words for which their psychological sense only emerges after one or more other senses have become established in the written language (secondary psychological words). To use a distinction made famous by Ebbinghaus, secondary psychological words have both a past and a history in psychology, while primary psychological words only have a history. Secondary psychological words have more connections to other words and occur more frequently in PsycINFO than do primary psychological words. For secondary psychological words, it is possible to trace a process of metaphoric polysemy that provides a basis for the eventual occurrence of the psychological sense of a word. Some primary psychological words are now developing secondary, nonpsychological senses, showing that they are subject to the same metaphoric process as are any other words.     

Factor analysis and the index of clustering

The initial problem of factor analysis is described as a search for clustering of the test vectors. Curves are developed which give a visual picture of the clustering tendency, and an index of clustering is derived which provides a simple estimate for the number of factors.Based, in part, on a paper Matrix Approximation Criteria read at the District meeting of the Psychometric Society, Chicago, April 3, 1937. The author wishes to acknowledge suggestions gained in conversations with Dr. A. S. Householder and Mr. Clyde Coombs, of the University of Chicago.     

Bilingual vocabulary size and lexical reading in Italian

In the present study we investigated how the vocabulary size of English–Italian bilinguals affects reading aloud in Italian (L2) modulating the reader's sensitivity to lexical aspects of the language. We divided adult bilinguals in two groups according to their vocabulary size (Larger — LV, and smaller — SV), and compared their naming performance to that of native Italian (NI) readers. In Experiment 1 we investigated the lexicality and word frequency effects in reading aloud. Similarly to NI, both groups of bilinguals showed these effects. In Experiment 2 we investigated stress assignment – which is not predictable by rule – to Italian words. The SV group made more stress errors in reading words with a non-dominant stress pattern compared to the LV group. The results suggest that the size of the reader's L2 lexicon affects the probability of correct reading aloud.