Publications

Abstract

Following up on an earlier positron emission tomography (PET) experiment (Indefrey et al., 2001), we used a scene description paradigm to investigate whether a posterior inferior frontal region subserving syntactic encoding for speaking is also involved in syntactic parsing during listening. In the language production part of the experiment, subjects described visually presented scenes
using either sentences, sequences of noun phrases, or sequences of syntactically unrelated words. In the language comprehension part of the experiment, subjects were auditorily presented with the same kinds of utterances and judged whether they matched the visual scenes. We were able to replicate the previous finding of a region in caudal Broca s area that is sensitive to the complexity of
syntactic encoding in language production. In language comprehension, no hemodynamic activation differences due to syntactic complexity were found. Given that correct performance in the judgment task did not require syntactic processing of the auditory stimuli, the results suggest that the degree to which listeners recruit syntactic processing resources in language comprehension may be a function of the syntactic demands of the task or the stimulus material.

Abstract

In order to separate the cognitive processes associated with phonological encoding and the use of a visual word form lexicon in reading, it is desirable to compare the processing of words presented in a visually familiar form with words in a visually unfamiliar form. Japanese Kana orthography offers this possibility. Two phonologically equivalent but visually dissimilar syllabaries allow the writing of, for example, foreign loanwords in two ways, only one of which is visually familiar. Familiarly written words, unfamiliarly written words, and pseudowords were presented in both Kana syllabaries (yielding six conditions in total) to participants during an fMRI measurement with a silent articulation task (Experiment 1) and a phonological lexical decision task (Experiment 2) using an event-related design. Consistent over two experimental tasks, the three different stimulus types (familiar, unfamiliar, and pseudoword) were found to activate selectively different brain regions previously associated with phonological encoding and word retrieval or meaning. Compatible with the predictions of the dual-route model for reading, pseudowords and visually unfamiliar words, which have to be read using phonological assembly, caused an increase in brain activity in left inferior frontal regions (BA 44/47), as compared to visually familiar words. Visually familiar and unfamiliar words were found to activate a range of areas associated with lexico-semantic processing more strongly than pseudowords, such as the left and right temporo-parietal region (BA 39/40), a region in the left middle/inferior temporal gyrus (BA 20/21), and the posterior cingulate (BA 31).

Abstract

Natural fast speech differs from normal-rate speech with respect to its temporal pattern. Previous results showed that word intelligibility of heavily artificially time-compressed speech could not be improved by making its temporal pattern more similar to that of natural fast speech. This might have been due to the extrapolation of timing rules for natural fast speech to rates that are much faster than can be attained by human speakers. The present study investigates whether, at a speech rate that human speakers can attain, artificially time-compressed speech is easier to process if its timing pattern is similar to that of naturally produced fast speech. Our first experiment suggests, however, that word processing speed was slowed down, relative to linear compression. In a second experiment, word processing of artificially time-compressed speech was compared with processing of naturally produced fast speech. Even when naturally produced fast speech is perfectly intelligible, its less careful articulation, combined with the changed timing pattern, slows down processing, relative to linearly time-compressed speech. Furthermore, listeners preferred artificially time-compressed speech over naturally produced fast speech. These results suggest that linearly time-compressed speech has both a temporal and a segmental advantage over natural fast speech.

Abstract

This study investigated the encoding of syllable boundary information during speech production in Dutch. Based on Levelt's model of phonological encoding, we hypothesized segments and syllable boundaries to be encoded in an incremental way. In a selfmonitoring experiment, decisions about the syllable affiliation (first or second syllable) of a pre-specified consonant, which was the third phoneme in a word, were required (e.g., ka.No canoe vs. kaN.sel pulpit ; capital letters indicate pivotal consonants, dots mark syllable boundaries). First syllable responses were faster than second syllable responses, indicating the incremental nature of segmental encoding and syllabification during speech production planning. The results of the experiment are discussed in the context of Levelt 's model of phonological encoding.

Abstract

Three experiments are reported that examined whether stem complexity plays a role in inflecting polymorphemic words in language production. Experiment 1 showed that preparation effects for words with polymorphemic stems are larger when they are produced among words with constant inflectional structures compared to words with variable inflectional structures and simple stems. This replicates earlier findings for words with monomorphemic stems (Janssen et al., 2002). Experiments 2 and 3 showed that when inflectional structure is held constant, the preparation effects are equally large with simple and compound stems, and with compound and complex adjectival stems. These results indicate that inflectional encoding is blind to the complexity of the stem, which suggests that specific inflectional rather than generic morphological frames guide the generation of inflected forms in speaking words.

Abstract

The authors report six implicit priming experiments that examined the production of inflected forms. Participants produced words out of small sets in response to prompts. The words differed in form or shared word-initial segments, which allowed for preparation. In constant inflectional sets, the words had the same number of inflectional suffixes, whereas in variable sets the number of suffixes differed. In the experiments, preparation effects were obtained, which were larger in the constant than in the variable sets. Control experiments showed that this difference in effect was not due to syntactic class or phonological form per se. The results are interpreted in terms of a slot-and-filler model of word production, in which inflectional frames, on the one hand, and stems and affixes, on the other hand, are independently spelled out on the basis of an abstract morpho-syntactic specification of the word, which is followed by morpheme-to-frame association.

Abstract

As people find their way through their environment, objects at navigationally relevant locations can serve as crucial landmarks. The parahippocampal gyrus has previously been shown to be involved in object and scene recognition. In the present study, we investigated the neural representation of navigationally relevant locations. Healthy human adults viewed a route through a virtual museum with objects placed at intersections (decision points) or at simple turns (non-decision points). Event-related functional magnetic resonance imaging (fMRI) data were acquired during subsequent recognition of the objects in isolation. Neural activity in the parahippocampal gyrus reflected the navigational relevance of an object's location in the museum. Parahippocampal responses were selectively increased for objects that occurred at decision points, independent of attentional demands. This increase occurred for forgotten as well as remembered objects, showing implicit retrieval of navigational information. The automatic storage of relevant object location in the parahippocampal gyrus provides a part of the neural mechanism underlying successful navigation.

Abstract

In this study, we use the association between various measures of the morphological family and decision latencies to reveal the way in which the components of Dutch and English compounds are processed. The results show that for constituents of concatenated compounds in both languages, a position-related token count of the morphological family plays a role, whereas English open compounds show an effect of a type count, similar to the effect of family size for simplex words. When Dutch compounds are written with an artificial space, they reveal no effect of type count, which shows that the differential effect for the English open compounds is not superficial. The final experiment provides converging evidence for the lexical consequences of the space in English compounds. Decision latencies for English simplex words are better predicted from counts of the morphological family that include concatenated and hyphenated but not open family members.

Abstract

Words can occur as constituents of other words. Some words have a high morphological productivity, in that they occur in many complex words, whereas others are morphological islands. Previous studies have found that the size of a word's morphological family can co-determine response latencies in lexical decision tasks. This thesis shows, using lexical decision as well as otherexperimental tasks, that the effect of family size is a semantic effect,reflecting the spreading of activation in the mental lexicon along the lines of morphological and semantic relatedness between words.

Abstract

In early Dutch learner varieties, there is no evidence of finiteness being a functional category. There is no V2nd: no correlation between inflectional morphology and movement. Initially, learners express the illocutive function of finiteness through the use of illocutive markers, with the non-use of an illocutive marker expressing the default illocutive function of assertion. Illocutive markers are functioning as adjuncts with scope over the predicate. Illocutive markers become re-analysed as functional elements.The driving force is the acquisition of the auxiliary verbs that occur with past participles. It leads to a reanalysis of illocutive markers as two separate elements: an auxiliary verb and a scope adverb. The (modal) auxiliary carries illocutive function. Lexical verb-argument structure (including the external argument) occurs within the domain of the auxiliary verb. The predicate as the focus constituent occurs within the domain of a scope adverb. This reanalysis establishes a position for the external argument within the domain of AUX. The acquisition of AUX causes the acquisition of a (hierarchical) structure with a complement as a constituent which represents an underlying verb-argument structure, a predicate as the domain of elements that are in focus, and an external (specifier) position as a landing site for elements with topic function.

Abstract

A series of experiments is reported in which subjects describe simple visual scenes by means of both sentential and non-sentential responses. The data support the following statements about the lexicalization (word finding) process. (1) Words used by speakers in overt naming or sentence production responses are selected by a sequence of two lexical retrieval processes, the first yielding abstract pre-phonological items (Ll -items), the second one adding their phonological shapes (L2-items). (2) The selection of several Ll-items for a multi-word utterance can take place simultaneously. (3) A monitoring process is watching the output of Ll-lexicalization to check if it is in keeping with prevailing constraints upon utterance format. (4) Retrieval of the L2-item which corresponds with a given LI-item waits until the Ld-item has been checked by the monitor, and all other Ll-items needed for the utterance under construction have become available. A coherent picture of the lexicalization process begins to emerge when these characteristics are brought together with other empirical results in the area of naming and sentence production, e.g., picture naming reaction times (Seymour, 1979), speech errors (Garrett, 1980), and word order preferences (Bock, 1982).

Abstract

Listeners cannot recognize highly reduced word forms in isolation, but they can do so when these forms are presented in context (Ernestus, Baayen, & Schreuder, 2002). This suggests that not all possible surface forms of words have equal status in the mental lexicon. The present study shows that the reduced forms are linked to the canonical representations in the mental lexicon, and that these latter representations induce reconstruction processes. Listeners restore suffixes that are partly or completely missing in reduced word forms. A series of phoneme-monitoring experiments reveals the nature of this restoration: the basis for suffix restoration is mainly phonological in nature, but orthography has an influence as well.

Abstract

This dissertation investigates two seemingly contradictory properties of the speech perception system. On the one hand, listeners are extremely sensitive to the fine phonetic details in the speech signal. These subtle acoustic cues can reduce the temporal ambiguity between words that show initial segmental overlap, and can guide lexical activation. On the other hand, comprehension does not seem to be hampered at all by the drastic reductions that typically occur in casual speech. Complete segments, and sometimes even complete syllables, may be missing, but comprehension is seemingly unaffected. This thesis aims at elucidating how words are represented and accessed in the mental lexicon, by investigating these contradictory phenomena for the domain of morphology

Abstract

Children must possess some ability to process input in a meaningful manner to acquire language. The present study reports on data from an experiment investigating 3- to 5-year-old English-speaking children's understanding of restrictive relative clauses manipulated for embeddedness and focus. The results of the study showed that English-speaking children acquire right-branching before center-embedded structures. Comparisons made with data from Portuguese-speaking children suggest general-cognitive and language-specific constraints on development, and with respect to English, a “clause expansion” approach to processing in development

Abstract

Drozd's critique of Crain & Thornton's (C&T) (1998) book Investigations in Universal Grammar (IUG) raises many issues concerning theory and experimental design within generative approaches to language acquisition. I focus here on one of the strongest theoretical claims of the Modularity Matching Model (MMM): continuity of processing. For reasons different to Drozd, I argue that the assumption is tenuous. Furthermore, I argue that the focus of the MMM and the methodological prescriptions contained in IUG are too narrow to capture language acquisition.

Abstract

Pauses during continuous speech, particularly those that occur within clauses, are thought to reflect the planning of forthcoming verbal output. We used functional Magnetic Resonance Imaging (fMRI) to examine their neural correlates. Six volunteers were scanned while describing seven Rorschach inkblots, producing 3 min of speech per inkblot. In an event-related design, the level of blood oxygenation level dependent (BOLD) contrast during brief speech pauses (mean duration 1.3 s, SD 0.3 s) during overt speech was contrasted with that during intervening periods of articulation. We then examined activity associated with pauses that occurred within clauses and pauses that occurred between grammatical junctions. Relative to articulation during speech, pauses were associated with activation in the banks of the left superior temporal sulcus (BA 39/22), at the temporoparietal junction. Continuous speech was associated with greater activation bilaterally in the inferior frontal (BA 44/45), middle frontal (BA 8) and anterior cingulate (BA 24) gyri, the middle temporal sulcus (BA 21/22), the occipital cortex and the cerebellum. Left temporal activation was evident during pauses that occurred within clauses but not during pauses at grammatical junctions. In summary, articulation during continuous speech involved frontal, temporal and cerebellar areas, while pausing was associated with activity in the left temporal cortex, especially when this occurred within a clause. The latter finding is consistent with evidence that within-clause pauses are a correlate of speech planning and in particular lexical retrieval.

Abstract

In John has left London, it is clear that the event in question, John's leaving London, has occurred in the past, for example yesterday at ten. Why is it impossible, then, to make this the event time more explicit by such an adverbial, as in Yesterday at ten, John has left London? Any solution of this puzzle crucially hinges on the meaning assigned to the perfect, and the present perfect in particular. Two such solutions, a scope solution and the 'current relevance'-solution, are discussed and shown to be inadequate. A new, strictly compositional analysis of the English perfect is suggested, and it is argued that the imcompatibility of the present perfect and most past tense adverbials has neither syntactic nor semantic reasons but follows from a simple pragmatical constraint, called here the 'position-definiteness constraint'. It is the very same constraint, which also makes an utterance such as At ten, John had left at nine pragmatically odd, even if John indeed had left at nine, and hence the utterance is true.

Abstract

Objectives: To investigate the time resolution of different methods for the computation of event-related desynchronization/synchronization (ERD/ERS), including one based on Hilbert transform. Methods: In order to better understand the time resolution of ERD/ERS, which is a function of factors such as the exact computation method, the frequency under study, the number of trials, and the sampling frequency, we simulated sudden changes in oscillation amplitude as well as very short and closely spaced events. Results: Hilbert-based ERD yields very similar results to ERD integrated over predefined time intervals (block ERD), if the block length is half the period length of the studied frequency. ERD predicts the onset of a change in oscillation amplitude with an error margin of only 10–30 ms. On the other hand, the time the ERD response needs to climb to its full height after a sudden change in oscillation amplitude is quite long, i.e. between 200 and 500 ms. With respect to sensitivity to short oscillatory events, the ratio between sampling frequency and electroencephalographic frequency band plays a major role. Conclusions: (1) The optimal time interval for the computation of block ERD is half a period of the frequency under investigation. (2) Due to the slow impulse response, amplitude effects in the ERD may in reality be caused by duration differences. (3) Although ERD based on the Hilbert transform does not yield any significant advantages over classical ERD in terms of time resolution, it has some important practical advantages.

Abstract

This study addresses the supralexical inferential processes underlying wellformedness judgements and latencies for a specic sublexical unit that appears in Dutch compounds, the interfix. Production studies have shown that the selection of interfixes in novel Dutch compounds and the speed of
this selection is primarily determined by the distribution of interfixes in existing compounds that share the left constituent with the target compound, i.e. the ‘‘left constituent family’’. In this paper, we consider the question whether constituent families also affect wellformedness decisions of novel as well as existing Dutch compounds in comprehension. We visually presented compounds containing interfixes that were either in line with the bias of the left constituent family or not. In the case of existing compounds, we also presented variants with replaced interfixes. As in production, the bias of the left constituent family emerged as a crucial predictor for both acceptance rates and response latencies. This result supports the hypothesis that, as in production, constituent families are (co-)activated in comprehension. We argue that this co-activation is part of a supralexical inferential process, and we discuss how our data might be interpreted within sublexical and supralexical theories of morphological processing.

Abstract

This study addresses the possibility that interfixes in multiconstituent nominal compounds in German and Dutch are functional as markers of immediate constituent structure.We report a lexical statistical survey of interfixation in the lexicons of German and Dutch which shows that all interfixes of German and one interfix of Dutch are significantly more likely to appear at the major constituent boundary than expected under chance conditions. A series of experiments provides evidence that speakers of German and Dutch are sensitive to the probabilistic cues to constituent structure provided by the interfixes. Thus, our data provide evidence that probability is part and parcel of grammatical competence.

Abstract

As in the case of other non-English languages, the study of the acquisition of Turkish has mostly focused on aspects of grammatical morphology and syntax, largely neglecting the study of the effect of interactional factors on child morphosyntax. This paper reviews indications from past research that studying input and adult-child discourse can facilitate the study of the acquisition of morphosyntax in the Turkish language. It also provides some recent studies of Turkish child language on the relationship of child-directed speech to the early acquisition of morphosyntax, and on the pragmatic features of a certain kind of discourse form in child-directed speech called variation sets.

Abstract

Chronic fatigue syndrome (CFS) is characterized by a debilitating fatigue of unknown aetiology. Patients who suffer from CFS report a variety of physical complaints as well as neuropsychological complaints. Therefore, it is conceivable that the CNS plays a role in the pathophysiology of CFS. The purpose of this study was to investigate neural correlates of CFS, and specifically whether there exists a linkage between disturbances in the motor system and CFS. We measured behavioural performance and cerebral activity using rapid event-related functional MRI in 16 CFS patients and 16 matched healthy controls while they were engaged in a motor imagery task and a control visual imagery task. CFS patients were considerably slower on performance of both tasks, but the increase in reaction time with increasing task load was similar between the groups. Both groups used largely overlapping neural resources. However, during the motor imagery task, CFS patients evoked stronger responses in visually related structures. Furthermore, there was a marked between-groups difference during erroneous performance. In both groups, dorsal anterior cingulate cortex was specifically activated during error trials. Conversely, ventral anterior cingulate cortex was active when healthy controls made an error, but remained inactive when CFS patients made an error. Our results support the notion that CFS may be associated with dysfunctional motor planning. Furthermore, the between-groups differences observed during erroneous performance point to motivational disturbances as a crucial component of CFS.

Abstract

The present study investigates hemispheric specialisation in the use of space in communicative gestures. For this purpose, we investigate split-brain patients in whom spontaneous and distinct right hand gestures can only be controlled by the left hemisphere and vice versa, the left hand only by the right hemisphere. On this anatomical basis, we can infer hemispheric specialisation from the performances of the right and left hands. In contrast to left hand dyspraxia in tasks that require language processing, split-brain patients utilise their left hands in a meaningful way in visuo-constructive tasks such as copying drawings or block-design. Therefore, we conjecture that split-brain patients are capable of using their left hands for the communication of the content of visuo-spatial animations via gestural demonstration. On this basis, we further examine the use of space in communicative gestures by the right and left hands. McNeill and Pedelty (1995) noted for the split-brain patient N.G. that her iconic right hand gestures were exclusively displayed in the right personal space. The present study investigates systematically if there is indication for neglect of the left personal space in right hand gestures in split-brain patients.

Abstract

The present study investigates hemispheric specialisation in the use of space in communicative gestures. For this purpose, we investigate split-brain patients in whom spontaneous and distinct right hand gestures can only be controlled by the left hemisphere and vice versa, the left hand only by the right hemisphere. On this anatomical basis, we can infer hemispheric specialisation from the performances of the right and left hands. In contrast to left hand dyspraxia in tasks that require language processing, split-brain patients utilise their left hands in a meaningful way in visuo-constructive tasks such as copying drawings or block-design. Therefore, we conjecture that split-brain patients are capable of using their left hands for the communication of the content of visuo-spatial animations via gestural demonstration. On this basis, we further examine the use of space in communicative gestures by the right and left hands. McNeill and Pedelty (1995) noted for the split-brain patient N.G. that her iconic right hand gestures were exclusively displayed in the right personal space. The present study investigates systematically if there is indication for neglect of the left personal space in right hand gestures in split-brain patients.

Abstract

This commentary on Alario et al. (2002) addresses two issues: (1) Different from what the authors suggest, there are no theories of production claiming the phonological word to be the upper bound of advance planning before the onset of articulation; (2) Their picture naming study of word frequency effects on speech onset is inconclusive by lack of a crucial control, viz., of object recognition latency. This is a perennial problem in picture naming studies of word frequency and age of acquisition effects

Abstract

How can one conceive of the neuronal implementation of the processing model we proposed in our target article? In his commentary (Pulvermüller 1999, reprinted here in this issue), Pulvermüller makes various proposals concerning the underlying neural mechanisms and their potential localizations in the brain. These proposals demonstrate the compatibility of our processing model and current neuroscience. We add further evidence on details of localization based on a recent meta-analysis of neuroimaging studies of word production (Indefrey & Levelt 2000). We also express some minor disagreements with respect to Pulvermüller’s interpretation of the “lemma” notion, and concerning his neural modeling of phonological code retrieval. Branigan & Pickering discuss important aspects of syntactic encoding, which was not the topic of the target article. We discuss their well-taken proposal that multiple syntactic frames for a single verb lemma are represented as independent nodes, which can be shared with other verbs, such as accounting for syntactic priming in speech production. We also discuss how, in principle, the alternative multiple-frame-multiplelemma account can be tested empirically. The available evidence does not seem to support that account.

Abstract

During the second half of the 19th century, the psychology of language was invented as a discipline for the sole purpose of explaining the evolution of spoken language. These efforts culminated in Wilhelm Wundt’s monumental Die Sprache of 1900, which outlined the psychological mechanisms involved in producing utterances and considered how these mechanisms could have evolved. Wundt assumes that articulatory movements were originally rather arbitrary concomitants of larger, meaningful expressive bodily gestures. The sounds such articulations happened to produce slowly acquired the meaning of the gesture as a whole, ultimately making the gesture superfluous. Over a century later, gestural theories of language origins still abound. I argue that such theories are unlikely and wasteful, given the biological, neurological and genetic evidence.

Abstract

This paper introduces a special issue of Cognition on lexical access in speech production. Over the last quarter century, the psycholinguistic study of speaking, and in particular of accessing words in speech, received a major new impetus from the analysis of speech errors, dysfluencies and hesitations, from aphasiology, and from new paradigms in reaction time research. The emerging theoretical picture partitions the accessing process into two subprocesses, the selection of an appropriate lexical item (a “lemma”) from the mental lexicon, and the phonological encoding of that item, that is, the computation of a phonetic program for the item in the context of utterance. These two theoretical domains are successively introduced by outlining some core issues that have been or still have to be addressed. The final section discusses the controversial question whether phonological encoding can affect lexical selection. This partitioning is also followed in this special issue as a whole. There are, first, four papers on lexical selection, then three papers on phonological encoding, and finally one on the interaction between selection and phonological encoding.

Abstract

Making a self-repair in speech typically proceeds in three phases. The first phase involves the monitoring of one’s own speech and the interruption of the flow of speech when trouble is detected. From an analysis of 959 spontaneous self-repairs it appears that interrupting follows detection promptly, with the exception that correct words tend to be completed. Another finding is that detection of trouble improves towards the end of constituents. The second phase is characterized by hesitation, pausing, but especially the use of so-called editing terms. Which editing term is used depends on the nature of the speech trouble in a rather regular fashion: Speech errors induce other editing terms than words that are merely inappropriate, and trouble which is detected quickly by the speaker is preferably signalled by the use of ‘uh’. The third phase consists of making the repair proper The linguistic well-formedness of a repair is not dependent on the speaker’s respecting the integriv of constituents, but on the structural relation between original utterance and repair. A bi-conditional well-formedness rule links this relation to a corresponding relation between the conjuncts of a coordination. It is suggested that a similar relation holds also between question and answer. In all three cases the speaker respects certain Istructural commitments derived from an original utterance. It was finally shown that the editing term plus the first word of the repair proper almost always contain sufficient information for the listener to decide how the repair should be related to the original utterance. Speakers almost never produce misleading information in this respect. It is argued that speakers have little or no access to their speech production process; self-monitoring is probably based on parsing one’s own inner or overt speech.

Abstract

Spontaneous self-corrections in speech pose a communication problem; the speaker must make clear to the listener not only that the original Utterance was faulty, but where it was faulty and how the fault is to be corrected. Prosodic marking of corrections - making the prosody of the repair noticeably different from that of the original utterance - offers a resource which the speaker can exploit to provide the listener with such information. A corpus of more than 400 spontaneous speech repairs was analysed, and the prosodic characteristics compared with the syntactic and semantic characteristics of each repair. Prosodic marking showed no relationship at all with the syntactic characteristics of repairs. Instead, marking was associated with certain semantic factors: repairs were marked when the original utterance had been actually erroneous, rather than simply less appropriate than the repair; and repairs tended to be marked more often when the set of items encompassing the error and the repair was small rather than when it was large. These findings lend further weight to the characterization of accent as essentially semantic in function.

Abstract

Recent work on sentence recognition suggests that listeners use their knowledge of the language to directly infer deep structure syntactic relations from surface structure markers. Suffixes may be such clues, especially in agglutinative languages. A cross-language (Dutch-Finnish) experiment is reported, designed to investigate whether the suffix structure of Finnish words (as opposed to suffixless Dutch words) can facilitate prompted recall of sentences in case these suffixes differentiate between possible deep structures. The experiment, in which 80 subjects recall sentences at the occasion of prompt words, gives only slight confirmatory evidence. Meanwhile, another prompted recall effect (Blumenthal's) could not be replicated.

Abstract

In his paper, MacKay reviews his Node Structure theory of error detection, but precedes it with a critical discussion of the Perceptual Loop theory of self-monitoring proposed in Levelt (1983, 1989). The present commentary is concerned with this latter critique and shows that there are more than casual problems with MacKay’s argumentation.

Abstract

Li and Gleitman (Turning the tables: language and spatial reasoning. Cognition, in press) seek to undermine a large-scale cross-cultural comparison of spatial language and cognition which claims to have demonstrated that language and conceptual coding in the spatial domain covary (see, for example, Space in language and cognition: explorations in linguistic diversity. Cambridge: Cambridge University Press, in press; Language 74 (1998) 557): the most plausible interpretation is that different languages induce distinct conceptual codings. Arguing against this, Li and Gleitman attempt to show that in an American student population they can obtain any of the relevant conceptual codings just by varying spatial cues, holding language constant. They then argue that our findings are better interpreted in terms of ecologically-induced distinct cognitive styles reflected in language. Linguistic coding, they argue, has no causal effects on non-linguistic thinking – it simply reflects antecedently existing conceptual distinctions. We here show that Li and Gleitman did not make a crucial distinction between frames of spatial reference relevant to our line of research. We report a series of experiments designed to show that they have, as a consequence, misinterpreted the results of their own experiments, which are in fact in line with our hypothesis. Their attempts to reinterpret the large cross-cultural study, and to enlist support from animal and infant studies, fail for the same reasons. We further try to discern exactly what theory drives their presumption that language can have no cognitive efficacy, and conclude that their position is undermined by a wide range of considerations.

Abstract

Infants point for various motives. Classically, one such motive is declarative, to share attention and interest with adults to events. Recently, some researchers have questioned whether infants have this motivation. In the current study, an adult reacted to 12-month-olds' pointing in different ways, and infants' responses were observed. Results showed that when the adult shared attention and interest (i.e. alternated gaze and emoted), infants pointed more frequently across trials and tended to prolong each point – presumably to prolong the satisfying interaction. However, when the adult emoted to the infant alone or looked only to the event, infants pointed less across trials and repeated points more within trials – presumably in an attempt to establish joint attention. Results suggest that 12-month-olds point declaratively and understand that others have psychological states that can be directed and shared.

Abstract

Attention-deficit/hyperactivity disorder (ADHD) and reading disability (RD) are common highly heritable disorders of childhood, which frequently co-occur. Data from twin and family studies suggest that this overlap is, in part, due to shared genetic underpinnings. Here, we report the first genome-wide linkage analysis of measures of reading ability in children with ADHD, using a sample of 233 affected sibling pairs who previously participated in a genome-wide scan for susceptibility loci in ADHD. Quantitative trait locus (QTL) analysis of a composite reading factor defined from three highly correlated reading measures identified suggestive linkage (multipoint maximum lod score, MLS>2.2) in four chromosomal regions. Two regions (16p, 17q) overlap those implicated by our previous genome-wide scan for ADHD in the same sample: one region (2p) provides replication for an RD susceptibility locus, and one region (10q) falls approximately 35 cM from a modestly highlighted region in an independent genome-wide scan of siblings with ADHD. Investigation of an individual reading measure of Reading Recognition supported linkage to putative RD susceptibility regions on chromosome 8p (MLS=2.4) and 15q (MLS=1.38). Thus, the data support the existence of genetic factors that have pleiotropic effects on ADHD and reading ability--as suggested by shared linkages on 16p, 17q and possibly 10q--but also those that appear to be unique to reading--as indicated by linkages on 2p, 8p and 15q that coincide with those previously found in studies of RD. Our study also suggests that reading measures may represent useful phenotypes in ADHD research. The eventual identification of genes underlying these unique and shared linkages may increase our understanding of ADHD, RD and the relationship between the two.

Abstract

The study investigated the neuronal basis of the retrieval of words from the mental lexicon. The semantic category interference effect was used to locate lexical retrieval processes in time and space. This effect reflects the finding that, for overt naming, volunteers are slower when naming pictures out of a sequence of items from the same semantic category than from different categories. Participants named pictures blockwise either in the context of same- or mixedcategory items while the brain response was registered using magnetoencephalography (MEG). Fifteen out of 20 participants showed longer response latencies in the same-category compared to the mixed-category condition. Event-related MEG signals for the participants demonstrating the interference effect were submitted to a current source density (CSD) analysis. As a new approach, a principal component analysis was applied to decompose the grand average CSD distribution into spatial subcomponents (factors). The spatial factor indicating left temporal activity revealed significantly different activation for the same-category compared to the mixedcategory condition in the time window between 150 and 225 msec post picture onset. These findings indicate a major involvement of the left temporal cortex in the semantic interference effect. As this effect has been shown to take place at the level of lexical selection, the data suggest that the left temporal cortex supports processes of lexical retrieval during production.

Abstract

Nyelv és/vagy evolúció: Lehetséges-e a nyelv evolúciós magyarázata? [Derek Bickerton: Nyelv és evolúció] (Magyari Lilla); Történelmi olvasókönyv az agyról [Charles G. Gross: Agy, látás, emlékezet. Mesék az idegtudomány történetéből] (Garab Edit Anna); Művészet vagy tudomány [Margitay Tihamér: Az érvelés mestersége. Érvelések elemzése, értékelése és kritikája] (Zemplén Gábor); Tényleg ésszerűek vagyunk? [Herbert Simon: Az ésszerűség szerepe az emberi életben] (Kardos Péter); Nemi különbségek a megismerésben [Doreen Kimura: Női agy, férfi agy]. (Hahn Noémi);

Abstract

Frames of reference are coordinate systems used to compute and specify the location of objects with respect to other objects. These have long been thought of as innate concepts, built into our neurocognition. However, recent work shows that the use of such frames in language, cognition and gesture varies crossculturally, and that children can acquire different systems with comparable ease. We argue that language can play a significant role in structuring, or restructuring, a domain as fundamental as spatial cognition. This suggests we need to rethink the relation between the neurocognitive underpinnings of spatial cognition and the concepts we use in everyday thinking, and, more generally, to work out how to account for cross-cultural cognitive diversity in core cognitive domains.

Abstract

In previous research it has been shown that subject relative clauses are easier to process than object relative clauses. Several theories have been proposed that explain the difference on the basis of different theoretical perspectives. However, previous research tested relative clauses only with animate protagonists. In a corpus study of Dutch and German newspaper texts, we show that animacy is an important determinant of the distribution of subject and object relative clauses. In two experiments in Dutch, in which the animacy of the object of the relative clause is varied, no difference in reading time is obtained between subject and object relative clauses when the object is inanimate. The experiments show that animacy influences the processing difficulty of relative clauses. These results can only be accounted for by current major theories of relative clause processing when additional assumptions are introduced, and at the same time show that the possibility of semantically driven analysis can be considered as a serious alternative.

Abstract

We describe a family-based sample of individuals with reading disability collected as part of a quantitative trait loci (QTL) mapping study. Eighty-nine nuclear families (135 independent sib-pairs) were identified through a single proband using a traditional discrepancy score of predicted/actual reading ability and a known family history. Eight correlated psychometric measures were administered to each sibling, including single word reading, spelling, similarities, matrices, spoonerisms, nonword and irregular word reading, and a pseudohomophone test. Summary statistics for each measure showed a reduced mean for the probands compared to the co-sibs, which in turn was lower than that of the population. This partial co-sib regression back to the mean indicates that the measures are influenced by familial factors and therefore, may be suitable for a mapping study. The variance of each of the measures remained largely unaffected, which is reassuring for the application of a QTL approach. Multivariate genetic analysis carried out to explore the relationship between the measures identified a common factor between the reading measures that accounted for 54% of the variance. Finally the familiality estimates (range 0.32–0.73) obtained for the reading measures including the common factor (0.68) supported their heritability. These findings demonstrate the viability of this sample for QTL mapping, and will assist in the interpretation of any subsequent linkage findings in an ongoing genome scan.

Abstract

Two eye-monitoring studies examined when unexpressed schematic participant information specified by verbs is used during sentence processing. Experiment 1 compared the processing of sentences with passive and intransitive verbs hypothesized to introduce or not introduce, respectively, an agent when their main clauses were preceded by either agent-dependent rationale clauses or adverbial clause controls. While there were no differences in the processing of passive clauses following rationale and control clauses, intransitive verb clauses elicited anomaly effects following agent-dependent rationale clauses. To determine whether the source of this immediately available schematic participant information is lexically specified or instead derived solely from conceptual sources associated with verbs, Experiment 2 compared the processing of clauses with passive and middle verbs following rationale clauses (e.g., To raise money for the charity, the vase was/had sold quickly…). Although both passive and middle verb forms denote situations that logically require an agent, middle verbs, which by hypothesis do not lexically specify an agent, elicited longer processing times than passive verbs in measures of early processing. These results demonstrate that participants access and interpret lexically encoded schematic participant information in the process of recognizing a verb.

Abstract

This thesis addressed the spoken production of complex numerals for time and space. The production of complex numerical expressions like those involved in telling time (e.g., 'quarter to four') or producing house numbers (e.g., 'two hundred forty-five') has been almost completely ignored. Yet, adult speakers produce such expressions on a regular basis in everyday communication. Thus, no theory on numerical cognition or speech production is complete without an account of the production of multi-morphemic utterances such as complex numeral expressions. The main question of this thesis is which particular speech planning levels are involved in the naming and reading of complex numerals for time and space. More specifically, this issue was investigated by examining different modes of response (clock times versus house numbers), alternative input formats (Arabic digit versus alphabetic format; analog versus digital clock displays), and different expression types (relative 'quarter to four' versus absolute 'three forty-five' time expressions).

Abstract

This study investigates how speakers of Dutch compute and produce relative time expressions. Naming digital clocks (e.g., 2:45, say ‘‘quarter to three’’) requires conceptual operations on the minute and hour information for the correct relative time expression. The interplay of these conceptual operations was investigated using a repetition priming paradigm. Participants named analog clocks (the primes) directly before naming digital clocks (the targets). The targets referred to the hour (e.g., 2:00), half past the hour (e.g., 2:30), or the coming hour (e.g., 2:45). The primes differed from the target in one or two hour and in five or ten minutes. Digital clock naming latencies were shorter with a five- than with a ten-min difference between prime and target, but the difference in hour had no effect. Moreover, the distance in minutes had only an effect for half past the hour and the coming hour, but not for the hour. These findings suggest that conceptual facilitation occurs when conceptual transformations are shared between prime and target in telling time.

Abstract

Argues that the Seneca accent system can be explained more simply and naturally if the foot structure is reanalyzed as trochaic. Determination of the position of the accent by the position and structure of the accented syllable and by the position and structure of the post-tonic syllable; Assignment of the pair of syllables which interact to predict where accent is assigned in different iambic feet.

Abstract

This paper aims to determine whether iconic tracing gestures produced while speaking constitute part of the speaker’s communicative intention. We used a picture description task in which speakers must communicate the spatial and color information of each picture to an interlocutor. By establishing the necessary minimal content of an intended message, we determined whether speech produced with concurrent gestures is less explicit than speech without gestures. We argue that a gesture must be communicatively intended if it expresses necessary information that was nevertheless omitted from speech. We found that speakers who produced iconic gestures representing spatial relations omitted more required spatial information from their descriptions than speakers who did not gesture. These results provide evidence that speakers intend these gestures to communicate. The results have implications for the cognitive architectures that underlie the production of gesture and speech.

Abstract

Spatial memory deficits are core features of aging-related changes in cognitive abilities. The neural correlates of these deficits are largely unknown. In the present study, we investigated the neural underpinnings of age-related differences in spatial memory by functional MRI using a navigational memory task with route encoding and route recognition conditions. We investigated 20 healthy young (18 - 29 years old) and 20 healthy old adults (53 - 78 years old) in a random effects analysis. Old subjects showed slightly poorer performance than young subjects. Compared to the control condition, route encoding and route recognition showed activation of the dorsal and ventral visual processing streams and the frontal eye fields in both groups of subjects. Compared to old adults, young subjects showed during route encoding stronger activations in the dorsal and the ventral visual processing stream (supramarginal gyrus and posterior fusiform/parahippocampal areas). In addition, young subjects showed weaker anterior parahippocampal activity during route recognition compared to the old group. In contrast, old compared to young subjects showed less suppressed activity in the left perisylvian region and the anterior cingulate cortex during route encoding. Our findings suggest that agerelated navigational memory deficits might be caused by less effective route encoding based on reduced posterior fusiform/parahippocampal and parietal functionality combined with diminished inhibition of perisylvian and anterior cingulate cortices correlated with less effective suppression of task-irrelevant information. In contrast, age differences in neural correlates of route recognition seem to be rather subtle. Old subjects might show a diminished familiarity signal during route recognition in the anterior parahippocampal region.

Abstract

Earlier work has shown that speakers naming several objects usually look at each of them before naming them (e.g., Meyer, Sleiderink, & Levelt, 1998). In the present study, participants saw pictures and described them in utterances such as "The chair next to the cross is brown", where the colour of the first object was mentioned after another object had been mentioned. In Experiment 1, we examined whether the speakers would look at the first object (the chair) only once, before naming the object, or twice (before naming the object and before naming its colour). In Experiment 2, we examined whether speakers about to name the colour of the object would look at the object region again when the colour or the entire object had been removed while they were looking elsewhere. We found that speakers usually looked at the target object again before naming its colour, even when the colour was not displayed any more. Speakers were much less likely to fixate upon the target region when the object had been removed from view. We propose that the object contours may serve as a memory cue supporting the retrieval of the associated colour information. The results show that a speaker's eye movements in a picture description task, far from being random, depend on the available visual information and the content and structure of the planned utterance.

Abstract

Phonological encoding in language production can be defined as a set of processes generating utterance forms on the basis of semantic and syntactic information. Most evidence about these processes stems from analyses of sound errors. In section 1 of this paper, certain important results of these analyses are reviewed. Two prominent models of phonological encoding, which are mainly based on speech error evidence, are discussed in section 2. In section 3, limitations of speech error analyses are discussed, and it is argued that detailed and comprehensive models of phonological encoding cannot be derived solely on the basis of error analyses. As is argued in section 4, a new research strategy is required. Instead of using the properties of errors to draw inferences about the generation of correct word forms, future research should directly investigate the normal process of phonological encoding.

Abstract

Tip-of-the-tongue states may represent the momentary unavailability of an otherwise accessible word or the weak activation of an otherwise inaccessible word. In three experiments designed to address these alternative views, subjects attempted to retrieve rare target words from their definitions. The definitions were followed by cues that were related to the targets in sound, by cues that were related in meaning, and by cues that were not related to the targets. Experiment 1 found that compared with unrelated cues, related cue words that were presented immediately after target definitions helped rather than hindered lexical retrieval, and that sound cues were more effective retrieval aids than meaning cues. Experiment 2 replicated these results when cues were presented after an initial target-retrieval attempt. These findings reverse a previous one (Jones, 1989) that was reproduced in Experiment 3 and shown to stem from a small group of unusually difficult target definitions.

Abstract

In this study we introduce an information-theoretical formulation of the emergence of type- and token-based effects in morphological processing. We describe a probabilistic measure of the informational complexity of a word, its information residual, which encompasses the combined influences of the amount of information contained by the target word and the amount of information carried by its nested morphological paradigms. By means of re-analyses of previously published data on Dutch words we show that the information residual outperforms the combination of traditional token- and type-based counts in predicting response latencies in visual lexical decision, and at the same time provides a parsimonious account of inflectional, derivational, and compounding processes.

Abstract

In this paper, we show that both token and type-based effects in lexical processing can result from a single, token-based, system, and therefore, do not necessarily reflect different levels of processing. We report three Simple Recurrent Networks modeling Dutch past-tense formation. These networks show token-based frequency effects and type-based analogical effects closely matching the behavior of human participants when producing past-tense forms for both existing verbs and pseudo-verbs. The third network covers the full vocabulary of Dutch, without imposing predefined linguistic structure on the input or output words.

Abstract

Finnish has a very productive morphology in which a stem can give rise to several thousand words. This study presents a visual lexical decision experiment addressing the processing consequences of the huge productivity of Finnish morphology. The authors observed that in Finnish words with larger morphological families elicited shorter response latencies. However, in contrast to Dutch and Hebrew, it is not the complete morphological family of a complex Finnish word that codetermines response latencies but only the subset of words directly derived from the complex word itself. Comparisons with parallel experiments using translation equivalents in Dutch and Hebrew showed substantial cross-language predictivity of family size between Finnish and Dutch but not between Finnish and Hebrew, reflecting the different ways in which the Hebrew and Finnish morphological systems contribute to the semantic organization of concepts in the mental lexicon.

Abstract

We describe the phenomenon of schwa-deletion in Hindi and how it is handled in the pronunciation component of a multilingual concatenative text-to-speech system. Each of the consonants in written Hindi is associated with an “inherent” schwa vowel which is not represented in the orthography. For instance, the Hindi word pronounced as [namak] (’salt’) is represented in the orthography using the consonantal characters for [n], [m], and [k]. Two main factors complicate the issue of schwa pronunciation in Hindi. First, not every schwa following a consonant is pronounced within the word. Second, in multimorphemic words, the presence of a morpheme boundary can block schwa deletion where it might otherwise occur. We propose a model for schwa-deletion which combines a general purpose schwa-deletion rule proposed in the linguistics literature (Ohala, 1983), with additional morphological analysis necessitated by the high frequency of compounds in our database. The system is implemented in the framework of finite-state transducer technology.

Abstract

Approximately 4% of English-speaking children are affected by specific language impairment (SLI), a disorder in the development of language skills despite adequate opportunity and normal intelligence. Several studies have indicated the importance of genetic factors in SLI; a positive family history confers an increased risk of development, and concordance in monozygotic twins consistently exceeds that in dizygotic twins. However, like many behavioral traits, SLI is assumed to be genetically complex, with several loci contributing to the overall risk. We have compiled 98 families drawn from epidemiological and clinical populations, all with probands whose standard language scores fall ⩾1.5 SD below the mean for their age. Systematic genomewide quantitative-trait–locus analysis of three language-related measures (i.e., the Clinical Evaluation of Language Fundamentals–Revised [CELF-R] receptive and expressive scales and the nonword repetition [NWR] test) yielded two regions, one on chromosome 16 and one on 19, that both had maximum LOD scores of 3.55. Simulations suggest that, of these two multipoint results, the NWR linkage to chromosome 16q is the most significant, with empirical P values reaching 10−5, under both Haseman-Elston (HE) analysis (LOD score 3.55; P=.00003) and variance-components (VC) analysis (LOD score 2.57; P=.00008). Single-point analyses provided further support for involvement of this locus, with three markers, under the peak of linkage, yielding LOD scores >1.9. The 19q locus was linked to the CELF-R expressive-language score and exceeds the threshold for suggestive linkage under all types of analysis performed—multipoint HE analysis (LOD score 3.55; empirical P=.00004) and VC (LOD score 2.84; empirical P=.00027) and single-point HE analysis (LOD score 2.49) and VC (LOD score 2.22). Furthermore, both the clinical and epidemiological samples showed independent evidence of linkage on both chromosome 16q and chromosome 19q, indicating that these may represent universally important loci in SLI and, thus, general risk factors for language impairment.

Abstract

The FOXP2 gene, located on human 7q31 (at the SPCH1 locus), encodes a transcription factor containing a polyglutamine tract and a forkhead domain. FOXP2 is mutated in a severe monogenic form of speech and language impairment, segregating within a single large pedigree, and is also disrupted by a translocation in an isolated case. Several studies of autistic disorder have demonstrated linkage to a similar region of 7q (the AUTS1 locus), leading to the proposal that a single genetic factor on 7q31 contributes to both autism and language disorders. In the present study, we directly evaluate the impact of the FOXP2 gene with regard to both complex language impairments and autism, through use of association and mutation screening analyses. We conclude that coding-region variants in FOXP2 do not underlie the AUTS1 linkage and that the gene is unlikely to play a role in autism or more common forms of language impairment.

Abstract

Specific language impairment (SLI) is defined as an unexplained failure to acquire normal language skills despite adequate intelligence and opportunity. We have reported elsewhere a full-genome scan in 98 nuclear families affected by this disorder, with the use of three quantitative traits of language ability (the expressive and receptive tests of the Clinical Evaluation of Language Fundamentals and a test of nonsense word repetition). This screen implicated two quantitative trait loci, one on chromosome 16q (SLI1) and a second on chromosome 19q (SLI2). However, a second independent genome screen performed by another group, with the use of parametric linkage analyses in extended pedigrees, found little evidence for the involvement of either of these regions in SLI. To investigate these loci further, we have collected a second sample, consisting of 86 families (367 individuals, 174 independent sib pairs), all with probands whose language skills are ⩾1.5 SD below the mean for their age. Haseman-Elston linkage analysis resulted in a maximum LOD score (MLS) of 2.84 on chromosome 16 and an MLS of 2.31 on chromosome 19, both of which represent significant linkage at the 2% level. Amalgamation of the wave 2 sample with the cohort used for the genome screen generated a total of 184 families (840 individuals, 393 independent sib pairs). Analysis of linkage within this pooled group strengthened the evidence for linkage at SLI1 and yielded a highly significant LOD score (MLS = 7.46, interval empirical P<.0004). Furthermore, linkage at the same locus was also demonstrated to three reading-related measures (basic reading [MLS = 1.49], spelling [MLS = 2.67], and reading comprehension [MLS = 1.99] subtests of the Wechsler Objectives Reading Dimensions).

Abstract

In four experiments, we examined the facilitation that occurs when spoken-word targets rhyme with preceding spoken primes. In Experiment 1, listeners’ lexical decisions were faster to words following rhyming words (e.g., ramp–LAMP) than to words following unrelated primes (e.g., pink–LAMP). No facilitation was observed for nonword targets. Targets that almost rhymed with their primes (foils; e.g., bulk–SULSH) were included in Experiment 2; facilitation for rhyming targets was severely attenuated. Experiments 3 and 4 were single-word shadowing variants of the earlier experiments. There was facilitation for both rhyming words and nonwords; the presence of foils had no significant influence on the priming effect. A major component of the facilitation in lexical decision appears to be strategic: Listeners are biased to say “yes” to targets that rhyme with their primes, unless foils discourage this strategy. The nonstrategic component of phonological facilitation may reflect speech perception processes that operate prior to lexical access.

Abstract

There is much evidence for the existence of multiple memory systems. However, it has been argued that tasks assumed to reflect different memory systems share basic processing components and are mediated by overlapping neural systems. Here we used multivariate analysis of PET-data to analyze similarities and differences in brain activity for multiple tests of working memory, semantic memory, and episodic memory. The results from two experiments revealed between-systems differences, but also between-systems similarities and within-system differences. Specifically, support was obtained for a task-general working-memory network that may underlie active maintenance. Premotor and parietal regions were salient components of this network. A common network was also identified for two episodic tasks, cued recall and recognition, but not for a test of autobiographical memory. This network involved regions in right inferior and polar frontal cortex, and lateral and medial parietal cortex. Several of these regions were also engaged during the working-memory tasks, indicating shared processing for episodic and working memory. Fact retrieval and synonym generation were associated with increased activity in left inferior frontal and middle temporal regions and right cerebellum. This network was also associated with the autobiographical task, but not with living/non-living classification, and may reflect elaborate retrieval of semantic information. Implications of the present results for the classification of memory tasks with respect to systems and/or processes are discussed.

Abstract

Typologies are critical tools for linguists, but typologies, like grammars, are known to leak. This book addresses the question of typological overlap from the perspective of a single language. In Lowland Chontal of Oaxaca, a language of southern Mexico, change events are expressed with three types of predicates, and each predicate type corresponds to a different language type in the well-known typology of lexicalization patterns established by Talmy and elaborated by others. O’Connor evaluates the predictive powers of the typology by examining the consequences of each predicate type in a variety of contexts, using data from narrative discourse, stimulus response, and elicitation. This is the first de­tailed look at the lexical and grammatical resources of the verbal system in Chontal and their relation to semantics of change. The analysis of how and why Chontal speakers choose among these verbal resources to achieve particular communicative and social goals serves both as a documentation of an endangered language and a theoretical contribution towards a typology of language use.

Abstract

We completed fine mapping of nine positional candidate regions for attention-deficit/hyperactivity disorder (ADHD) in an extended population sample of 308 affected sibling pairs (ASPs), constituting the largest linkage sample of families with ADHD published to date. The candidate chromosomal regions were selected from all three published genomewide scans for ADHD, and fine mapping was done to comprehensively validate these positional candidate regions in our sample. Multipoint maximum LOD score (MLS) analysis yielded significant evidence of linkage on 6q12 (MLS 3.30; empiric P=.024) and 17p11 (MLS 3.63; empiric P=.015), as well as suggestive evidence on 5p13 (MLS 2.55; empiric P=.091). In conjunction with the previously reported significant linkage on the basis of fine mapping 16p13 in the same sample as this report, the analyses presented here indicate that four chromosomal regions—5p13, 6q12, 16p13, and 17p11—are likely to harbor susceptibility genes for ADHD. The refinement of linkage within each of these regions lays the foundation for subsequent investigations using association methods to detect risk genes of moderate effect size.