Bootstrapping the lexicon: a computational model of infant speech segmentation

Prelinguistic infants must find a way to isolate meaningful chunks from the continuous streams of speech that they hear. BootLex, a new model which uses distributional cues to build a lexicon, demonstrates how much can be accomplished using this single source of information. This conceptually simple probabilistic algorithm achieves significant segmentation results on various kinds of language corpora - English, Japanese, and Spanish; child- and adult-directed speech, and written texts; and several variations in coding structure - and reveals which statistical characteristics of the input have an influence on segmentation performance. BootLex is then compared, quantitatively and qualitatively, with three other groups of computational models of the same infant segmentation process, paying particular attention to functional characteristics of the models and their similarity to human cognition. Commonalities and contrasts among the models are discussed, as well as their implications both for theories of the cognitive problem of segmentation itself, and for the general enterprise of computational cognitive modeling.     

Whole word morphologizer: expanding the word-based lexicon: a nonstochastic computational approach

Whole Word Morphologizer is a small computer implementation of word-based morphology. The program automatically identifies morphological relations in a small word-based lexicon, literally learning its morphology, and uses the knowledge it acquires to generate new words. It is based on a model of the mental lexicon in which all entries are whole, entire, fully fledged words and relies solely on basic cognitive principles (differentiation and generalization) for the automatic acquisition of morphological relations and the population of the lexicon.     

A multimethod investigation of the behavioral activation system in bipolar disorder

Dysregulation in behavioral activation system (BAS) activity has been implicated in the pathogenesis of bipolar disorder (BPD). To characterize BAS activity and related facets in this disorder, the authors compared 59 participants with BPD to 44 controls on multiple measures of BAS activity, including a standardized behavioral task, self-reports, and electroencephalographic indexes of regional cortical activity. Levels of putative BAS activity differed depending on assessment strategy. When a behavioral task indexing reward sensitivity was used, euthymic BPD patients showed evidence of higher BAS activity than either control participants or patients who were in a mood episode. Following a mood induction procedure designed to elicit BAS activity, currently episodic patients showed relatively greater left anterior cortical activity than either euthymic or control participants. Implications of the findings for future research on BPD vulnerability are described.     

Impaired activation of the phonological lexicon: effects upon oral reading

The role of the phonological lexicon in oral reading is examined in a patient with a small focal left hemisphere lesion. Impaired access to the patient's phonological lexicon is suggested by a number of findings, including the production of phonemic errors across a variety of tasks; increasing difficulty in word production with increasing word length; and difficulty on tests of homophone and rhyme judgments. Two competing models of reading are tested: the nonlexical ("rules") and the lexical ("no-rules") models. The rules model predicts that a disturbance in the phonological lexicon will result in surface alexia; the no-rules model predicts phonological alexia. Results indicate that the patient's reading is most similar to phonological alexia, providing support for the no-rules model. The applicability of the no-rules model to other forms of acquired alexia is explored.     

Stem allomorphy in the Spanish mental lexicon: evidence from behavioral and ERP experiments

This study presents results from a nonce-word elicited production task and a reading experiment using event-related brain potentials (ERPs) investigating finite forms of Spanish verbs which consist of marked stems and regular person and number agreement suffixes. The first experiment showed that unmarked stems are productively extended to nonce words, whereas marked stems generalize more restrictively to nonce words, based on lexical similarity to existing stem forms. The second experiment yielded a lexical ERP signature for stem violations and an ERP pattern signaling morpho-syntactic (rule-based) processing for suffix violations. We argue that stem allomorphy is lexically represented in the Spanish mental lexicon, with marked stems forming subnodes of structured lexical entries.     

Semantic features and semantic categories: differences in rapid activation of the lexicon.

Robust priming was shown in a semantic categorization task for prime-target pairs which shared semantic features (e.g., pumpkin-squash). Priming facilitation for these pairs was demonstrated at extremely rapid prime exposures (28 and 43 ms) and increased with prime duration. The onset and amount of facilitation differed significantly for these semantic, nonassociative pairs and for associative-semantic prime-target pairs (e.g., cow-bull). The latter pairs produced facilitation, but later (at prime-target SOAs of 70 and 200 ms) and of lesser magnitude. These results are discussed in relation to three current models of semantic memory: spreading activation, compound cue, and distributed models.     

A further investigation of the filled-duration illusion with a comparison between children and adults

This study investigated the filled duration illusion in children in comparison to adults, using a temporal bisection task with two ranges of anchor durations (1 vs. 4s and 2 vs. 8s). The results revealed a marked filled duration effect when filled and empty durations were presented in the same session (within-subjects condition), with the filled durations being judged to be longer than the empty durations in all age groups. However, the magnitude of this effect appeared to be larger in the children than in the adults. Furthermore, the filled duration effect decreased with the longest duration stimuli, and apparent reversals of this effect were observed with the empty durations being judged longer. In the between-subjects experiment, the filled duration effect disappeared in all age groups. However, in the children, the variability in the temporal judgment appeared to be greater for the empty than for the filled durations, thus indicating a lower sensitivity to empty durations.     

Near-death experiences and religion: A further investigation

The relationship between religion and near-death experiencers (NDEs) was examined by interviewing 40 near-death experiences who were given a series of instruments to measure religious orientation and religious change. No relationship was found between religious orientation prior to the NDE and the depth of the NDE. However, a significant correlation was found between the depth of the NDE and a subsequent increase both in the importance of religion and in religious activity. Various theoretical explanations of NDEs were examined to account for these findings.     

A further investigation of the life-world

Conclusions My personal way to phenomenology revealed to me qualities that seem to be essential to one's sense of everyday social reality. Having been victimized I became aware of some of the basic elements that lie beneath the intersubjectivity of the taken-for granted life-world.Death is the ultimate problematic event and the individual is shielded from it by his or her life-world. We hope that actions are repeatable and that others are trustworthy so that we will not confront our own isolation and our own mortality. Although one is alone in death, we act as if we are, and always will be, fundamentally with others within a shared and orderly social world. In short, we avoid our finite individuality through the hopeful construction of a sense of permanent and fundamental sociability. By sheltering ourselves within the life-world, we are, in essence, hoping that we will not die. In this sense, the life-world is a fundamentally deceptive construction. Yet, in this same sense, the life-world is also the source of social and cultural progress. Paradoxically, our sense of everyday reality is both deceptive and productive.The author wishes to express his gratitude to Susan Meisenhelder, George Psathas, and Richard Zaner for their comments on earlier drafts of this paper.     

Distinctiveness and correlation in conceptual structure: behavioral and computational studies

Patients with category-specific deficits have motivated a range of hypotheses about the structure of the conceptual system. One class of models claims that apparent category dissociations emerge from the internal structure of concepts rather than fractionation of the system into separate substores. This account claims that distinctive properties of concepts in the living domain are vulnerable because of their weak correlation with other features. Given the assumption that mutual activation among correlated properties produces faster activation in the normal system, the authors predicted a disadvantage for the distinctive features of living things for unimpaired adults. Results of a speeded feature verification study supported this prediction, as did a computational simulation in which networks mapped from orthography to semantics.     

Psychometric evaluation of the behavioral inhibition/behavioral activation scales in a large sample of outpatients with anxiety and mood disorders

The latent structure, reliability, and validity of the Behavioral Inhibition/Behavioral Activation Scales (BIS/BAS; C. L. Carver and T. L. White, 1994) were examined in a large sample of outpatients (N = 1,825) with anxiety and mood disorders. Four subsamples were used for exploratory and confirmatory factor analyses. In addition to generally upholding a latent structure found previously in nonclinical samples, results indicated measurement invariance of the BIS/BAS between genders and a higher order structure of the BAS scales. Convergent and discriminant validity of the BIS/BAS were supported by findings that the subscales correlated most strongly with measures of neighboring personality constructs (e.g., BIS with neuroticism, BAS with positive affect) than with measures of current anxiety and depression symptoms. Overall, the results support the psychometric properties of the BIS/BAS in this clinical sample.     

Developmental auditory agnosia in the severely retarded: A further investigation

The hypotheses were investigated that (a) ability to recognize the auditory perceptual stimuli for familiar events is a developmental correlate to language acquisition and (b) the low functioning mentally handicapped suffer from auditory agnosia and are impaired in this ability. The subjects were 42 nonretarded children of ages 3 through 6 and 53 severely and moderately retarded, noninstitutionalized students. The retarded subjects were matched by mental age to the chronological age of the nonretarded children. The stimuli were 49 environmental sounds; the task consisted of sound-and-picture matching-to-sample. Group membership and developmental age were the factors in an analysis of variance design. The results revealed a strong effect of developmental age (p <. 0001). The effect of group was not significant, indicating that auditory agnosia may not be common among the lower functioning retarded. The assumption that agnosia may be a major factor underlying the language disability of the severely retarded was reexamined. It was suggested that the severely retarded achieve the requisite perceptual-semantic knowledge base for language too late, after the critical age for spontaneous and efficient language learning has passed.