Opening the black box: why we need a PBL talkbank database.

BACKGROUND: Interest runs high these days in developing "evidence-based" reviews to provide guidelines for instructional practice. However, we lack careful documentation of the ways in which the practices of problem-based learning (PBL) vary across groups and across implementations. A necessary starting point for developing any sweeping conclusions about the efficacy of PBL as an instructional innovation, therefore, is that we begin to become more articulate about what it is that people do when they say they are doing PBL. SUMMARY: A proposal is offered for a new initiative in medical education research, one focused on documenting the range of practices employed in different implementations of PBL. A vital facet of this initiative would be the development of a shared corpus of video recordings referred to here as the "PBL TalkBank database." CONCLUSIONS: We propose that medical educators adopt the tradition employed in linguistics and communication studies of creating shared data corpora. The corpus in this case would consist of recordings, transcripts, and research notes documenting PBL practices in different PBL curricula. Preliminary work has been undertaken to develop such a database, and we invite the participation of other researchers.

STEP--a System for Teaching Experimental Psychology using E-Prime.

Students in psychology need to learn to design and analyze their own experiments. However, software that allows students to build experiments on their own has been limited in a variety of ways. The shipping of the first full release of the E-Prime system later this year will open up a new opportunity for addressing this problem. Because E-Prime promises to become the standard for building experiments in psychology, it is now possible to construct a Web-based resource that uses E-Prime as the delivery engine for a wide variety of instructional materials. This new system, funded by the National Science Foundation, is called STEP (System for the Teaching of Experimental Psychology). The goal of the STEP Project is to provide instructional materials that will facilitate the use of E-Prime in various learning contexts. We are now compiling a large set of classic experiments implemented in E-Prime and available over the Internet from http://step.psy.cmu.edu. The Web site also distributes instructional materials for building courses in experimental psychology based on E-Prime.

Developmental differences in visual and auditory processing of complex sentences.

Children aged 8 through 11 (N = 250) were given a word-by-word sentence task in both the visual and auditory modes. The sentences included an object relative clause, a subject relative clause, or a conjoined verb phrase. Each sentence was followed by a true-false question, testing the subject of either the first or second verb. Participants were also given two memory span measures: digit span and reading span. High digit span children slowed down more at the transition from the main to the relative clause than did the low digit span children. The findings suggest the presence of a U-shaped learning pattern for on-line processing of restrictive relative clauses. Off-line accuracy scores showed different patterns for good comprehenders and poor comprehenders. Poor comprehenders answered the second verb questions at levels that were consistently below chance. Their answers were based on an incorrect local attachment strategy that treated the second noun as the subject of the second verb. For example, they often answered yes to the question "The girl chases the policeman" after the object relative sentence "The boy that the girl sees chases the policeman." Interestingly, low memory span poor comprehenders used the local attachment strategy less consistently than high memory span poor comprehenders, and all poor comprehenders used this strategy less consistently for harder than for easier sentences.

The task dependence of staged versus cascaded processing: an empirical and computational study of Stroop interference in speech production.

The authors investigated the on-line relationship between overt articulation and the central processes of speech production. In 2 experiments manipulating the timing of Stroop interference in color naming, the authors found that naming behavior can shift between exhibiting a staged or cascaded mode of processing, depending on task demands: An effect of Stroop interference on naming durations arose only when there was increased pressure for speeded responding. In a simple connectionist model of information processing applied to color naming, the authors accounted for the current results by manipulating a single parameter, termed "gain," modulating the rate of information accrual within the network. Results are discussed in relation to mechanisms of strategic control and the link between cognition and action.

Phonological priming in children's picture naming.

Two experiments examined phonological priming in children and adults, using a cross-modal picture-word interference task. Pictures of familiar objects were presented on a computer screen, while interfering words (IWs) were presented over headphones. In terms of their relation to target pictures, IWs were either phonologically related, unrelated, neutral (the word go), or identical. Ninety children (30 aged 4;11 to 5;11, 30 aged 6;11 to 7;11, and 30 aged 9;5 to 11;9) and 30 adults were instructed to name the pictures as quickly as possible while ignoring the IWs. In Experiment 1, related IWs shared onset consonants with the names of the pictures. Across ages, participants named pictures faster with related IWs than with unrelated IWs. In Experiment 2, related IWs rhymed with the targets. Here, only the youngest children (five to seven-year-olds) named pictures faster with related IWs than with unrelated IWs. The results indicate that priming effects reach a peak during a time when articulatory information is being consolidated in the output phonological buffer. The disappearance of the rhyme priming effect with age may reflect the gradual emergence of the onset as an organizing structure in speech production. This increased prominence of the onset can be viewed as one component of a just-in-time, incrementalist approach to speech production that allows adults to speak more fluently than children.

Online measures of basic language skills in children with early focal brain lesions.

Twenty children with early focal lesions were compared with 150 age-matched control subjects on 11 online measures of the basic skills underlying language processing, a digit span task, and 6 standardized measures. Although most of the children with brain injury scored within the normal range on the majority of the tasks, they also had a disproportionately high number of outlier scores on the reaction time tests. This evidence for a moderate impairment of the basic skills underlying language processing contrasts with other evidence suggesting that these children acquire normal control of the functional use of language. Furthermore, these children scored within the normal range on a measure of general cognitive ability, suggesting that there is no particular sparing of linguistic functions at the expense of general cognitive functions. Using the MPD procedure (Valdés-Pérez & Pericliev, 1997), we found that the controls and the five clinical groups could be best distinguished with two measures of online processing (word repetition and visual number naming) and one standardized test subcomponent (the CELF Oral Directions subtest). The 12 children with left hemisphere lesions scored significantly lower than the 8 other children on the CELF-RS measure. Within the group of children with cerebral infarct, the nature of the processing disability could be linked fairly well to site of lesion. Otherwise, there was little relation between site or size of lesion and the pattern of deficit. These results support a model in which damage to the complex functional circuits subserving language leads to only minor deficits in process efficiency, because of the plasticity of developmental processes.

Developmental and lesion effects in brain activation during sentence comprehension and mental rotation.

The development of neurocognitive networks was examined in 2 cognitive paradigms: auditory sentence comprehension and mental rotation of alphanumeric stimuli. Patterns of brain activation were measured with whole brain echoplanar functional magnetic resonance imaging at 3 Tesla in 5 adults (20-28 years old), 7 children (9-12 years old), and 6 pediatric patients (9-12 years old) with perinatal strokes or periventricular hemorrhages. Healthy children and adults activated similar neurocognitive networks, but there were developmental differences in the distribution of activity across these networks. In the sentence task, children showed more activation in the inferior visual area suggesting an imagery strategy rather than a linguistic strategy for sentence processing. Furthermore, consistent use of a sentence comprehension strategy, whether correct or incorrect as compared to chance performance, was associated with greater activation in the inferior frontal area (Broca's) in both children and pediatric patients. In the mental rotation task, healthy adults showed more activation in the superior parietal and middle frontal areas and less activation in the supramarginal gyrus, suggesting adults were primarily engaged in visual-spatial manipulation and less engaged in the recognition of noncanonical views of stimuli. The pediatric patients showed patterns of activation consistent with organization of cognitive processing into homologous areas of the contralateral hemisphere.

Functional organization of activation patterns in children: whole brain fMRI imaging during three different cognitive tasks.

1. Patterns of brain activation were measured with whole brain echo-planar functional magnetic resonance imaging (fMRI) at 3.0 Tesla in healthy children (N = 6) and in one child with a left-hemisphere encephalomalacic lesion as sequellae from early stroke. 2. Three cognitive tasks were used: auditory sentence comprehension, verb generation to line drawings, and mental rotation of alphanumeric stimuli. 3. There was evidence for significant bilateral activation in all three cognitive tasks for the healthy children. Their patterns of activation were consistent with previous functional imaging studies with adults. 4. The child with a left-hemisphere stroke showed evidence of homologous organization in the non-damaged hemisphere.

Quick, automatic, and general activation of orthographic and phonological representations in young readers.

Second through 6th graders were presented with nonword primes (orthographic, pseudohomophone, and control) and target words displayed for durations (30 and 60 ms) that were brief enough to prevent complete processing. Word reading skills were assessed by 3 word and nonword naming tasks. Good readers exhibited more orthographic priming than poor readers at both durations and more pseudohomophone priming at the short duration only. This suggests that good readers activate letter and phonemic information more efficiently than poor readers. Good readers also exhibited an equal amount of priming at both durations, whereas poor readers showed greater priming at the longer duration. This suggests that activation was not under strategic control. Finally, priming was reliable for both high- and low-frequency targets. This suggests that readers activate consistent information regardless of target word characteristics. Thus, quick, automatic, and general activation of orthographic and phonological information in skilled readers results from the precision and redundancy of their lexical representations.

Sentence processing strategies in children with expressive and expressive-receptive specific language impairments.

The purpose of this study was to investigate the sentence comprehension strategies used by children with expressive and expressive-receptive specific language impairments (SLI) within a language processing framework. Fourteen children with SLI (ages 6;10-7;11) meeting strict selection criteria were compared to seven age-matched and seven younger normal controls. Children were asked to determine the agent in sentences composed of two nouns and a verb (NVN, NNV, VNN) with animacy of the noun as a second factor. Results of group comparisons revealed that children with E-SLI and ER-SLI differed from each other in the comprehension strategies they employed as well as differing from both age-matched and younger normal language control groups. Children with E-SLI relied exclusively on a first noun as agent strategy across all conditions, whereas children with ER-SLI used animacy cues when available. Additionally, maximum likelihood estimates were calculated to investigate individual patterns of performance under different cue conditions. Results revealed a significant correlation between severity of receptive language abilities and the type of strategy used, with better receptive language skills being highly correlated with children's use of word order cues.

Models of the emergence of language.

Recent work in language acquisition has shown how linguistic form emerges from the operation of self-organizing systems. The emergentist framework emphasizes ways in which the formal structures of language emerge from the interaction of social patterns, patterns implicit in the input, and pressures arising from general aspects of the cognitive system. Emergentist models have been developed to study the acquisition of auditory and articulatory patterns during infancy and the ways in which the learning of the first words emerges from the linkage of auditory, articulatory, and conceptual systems. Neural network models have also been used to study the learning of inflectional markings and basic syntactic patterns. Using both neural network modeling and concepts from the study of dynamic systems, it is possible to analyze language learning as the integration of emergent dynamic systems.

Vocabulary acquisition and verbal short-term memory: computational and neural bases.

In this paper, we explore the hypothesis that human vocabulary acquisition processes and verbal short-term memory abilities utilize a common cognitive and neural system. We begin by reviewing behavioral evidence for a shared set of processes. Next, we examine what the computational bases of such a shared system might be and how vocabulary acquisition and verbal short-term memory might be related in mechanistic terms. We examine existing computational models of vocabulary acquisition and of verbal short-term memory, concluding that they fail to adequately relate these two domains. We then propose an alternative model which accounts not only for the relationship between word learning and verbal short-term memory, but also for a wide range of phenomena in verbal short-term memory. Furthermore, this new account provides a clear statement of the relationship between the proposed system and mechanisms of language processing more generally. We then consider possible neural substrates for this cognitive system. We begin by reviewing what is known of the neural substrates of speech processing and outline a conceptual framework within which a variety of seemingly contradictory neurophysiological and neuropsychological findings can be accommodated. The linkage of the shared system for vocabulary acquisition and verbal short-term memory to neural areas specifically involved in speech processing lends further support to our functional-level identification of the mechanisms of vocabulary acquisition and verbal short-term memory with those of language processing. The present work thus relates vocabulary acquisition and verbal short-term memory to each other and to speech processing, at a cognitive, computational, and neural level.

The PsyScope experiment-building system.

PsyScope is a system for building behavioral experiments on the Apple Macintosh computer using a graphic user interface that requires no computer programming. The program supports a wide variety of experimental designs, multimedia formats, and stimulus control. A freeware version is available at the author's web site.

The wheat and the chaff: or four confusions regarding CHILDES.

Edwards (1992) presents a set of examples from the Child Language Data Exchange System (CHILDES) as prototypes of bad transcription practice. Her discussion is based upon four basic confusions. First, Edwards confuses old and discarded versions of CHAT with current CHAT. Second, she confuses the relation between CHAT standards with the implementation of these standards during the process of reformatting older corpora. Third, she confuses transcription for automatic analysis with transcription for documentation. Fourth, she confuses the CHAT guidelines with the larger CHILDES system. We argue that these confusions have misled Edwards into developing an overly rigid set of principles for data analysis which, if followed literally, could choke off progress in the analysis of spontaneous language samples.

Inflectional marking in Hungarian aphasics.

How do aphasics deal with the rich inflectional marking available in agglutinative languages like Hungarian? For the Hungarian noun alone, aphasics have to deal with over 15 basic case markings and dozens of possible combinations of these basic markings. Using the picture description task of MacWhinney and Bates (1978), this study examined the use of inflectional markings in nine Broca's and five Wernicke's aphasic speakers of Hungarian. The analysis focused on subject, direct object, indirect object, and locative nominal arguments. Compared to normals, both groups had a much higher rate of omission of all argument types. Subject ellipsis was particularly strong, as it is in normal Hungarian. There was a tendency for Broca's to omit the indirect object and for Wernicke's to omit the direct object. Across argument types, Wernicke's had a much higher level of pronoun usage than did Broca's. Broca's also showed a very high level of article omission. Compared to similar data reported by Slobin (this issue) for Turkish, the Hungarian aphasics showed an elevated level of omission of case markings. Addition errors were quite rare, but there were 14 substitutions of one case marking for another. These errors all involved the substitution of some close semantic competitor. There were no errors in the basic rules for vowel harmony or morpheme order. Overall the results paint a picture of a group of individuals whose grammatical abilities are damaged and noisy, but still largely functional. Neither the view of Broca's as agrammatic nor the view of Wernicke's as paragrammatic was strongly supported.

Sentence comprehension in aphasia in two clear case-marking languages.

Studies of aphasia in Indo-European languages point to a selective vulnerability of morphological case marking in sentence comprehension. However, in case-marking languages such as German and Serbo-Croatian, the use of case marking to express formal grammatical gender diminishes the clarity of grammatical role marking. In Hungarian and Turkish, there are simple and reliable markings for the direct object. These markings are not linked to grammatical gender. Compared to Hungarian, the Turkish accusative marking is somewhat lower in availability, but somewhat higher in detectability. The processing of these cues by aphasics was tested using the design of MacWhinney, Pléh, and Bates (1985. Cognitive Psychology, 17, 178-209). Simple sentences with two nouns and one transitive verb were read to Broca's and Wernicke's aphasics, anomics, and control subjects in both Turkey and Hungary. The main effect of case marking was extremely strong. However, this was not true for all groups. The aphasics used the case cue far less than the normals, with the Hungarian Wernicke's group showing the greatest loss. Word order variations were largely ignored in all groups whenever the case-marking cue was present. When case marking was absent, Turkish subjects had a clear SOV interpretation for NNV sentences and Hungarians had a clear SVO interpretation for NVN sentences, in accord with basic patterns in their languages. When there was a contrast between the animacy of the two nouns, subjects choose the animate nouns significantly more often. The effect of animacy was particularly strong in Turkish, in accord with basic facts of Turkish grammar. In Hungarian, VNN sentences without case marking were interpreted as VOS when the first noun was inanimate. In Turkish, VNN sentences without case marking were often interpreted as VSO. In general, the aphasic subjects showed a clear preservation of virtually all aspects of their native languages, albeit in a much noisier form. Despite the high reliability of the case-marking cue, it was damaged more than the word order cue in English subjects. The near-chance processing of the case cue by the Wernicke's aphasics in Hungarian can probably be attributed to the relatively greater difficulty involved in detecting the Hungarian accusative suffix.