The subject of this dissertation is the assessment and optimization of image quality for multiple-pinhole, multiple-camera SPECT systems. These systems collect gamma-ray photons emitted from an object using pinhole apertures. Conventional measures of image quality, such as the signal-to-noise ratio or the modulation transfer function, do not predict how well a system's images can be used to perform a relevant task. This dissertation takes the stance that the ultimate measure of image quality is to measure how well images produced from a system can be used to perform a task. Furthermore, we recognize that image quality is inherently a statistical concept that must be assessed for the average task performance across a large ensemble of images.The tasks considered in this dissertation are detection tasks. Namely we consider detecting a known three-dimensional signal embedded in a three-dimensional stochastic object using the Bayesian ideal observer. Out of all possible observers (human or otherwise) the ideal observer sets the absolute upper bound for detection task performance by using all possible information in the image data. By employing a stochastic object model we can account for the effects of object variability, which has a large effect on observer performance.An imaging system whose hardware has been optimized for ideal observer detection task performance is an imaging system that maximally transfers detection task relevant information to the image data.The theory and simulation of image quality, detection tasks, and gamma-ray imaging are presented. Assessments of ideal observer detection task performance are used to optimize imaging hardware for SPECT systems as well as to rank different imaging system designs.

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The process of generating a phonological code from print is widely described as automatic. This claim is tested in Chapter 1 by assessing whether phonological recoding uses central attention in the context of the Psychological Refractory Period (PRP) paradigm. Task 1 was a tone discrimination task and Task 2 was reading aloud. Nonword letter length and grapheme-phoneme complexity yielded additive effects with SOA in Experiments 1 and 2 suggesting that <em>assembled phonology</em> uses central attention. Neighborhood density (N) yielded additive effects with SOA in Experiments 3 and 4, suggesting that one form of lexical contribution to phonological recoding also uses central attention. Taken together, the results of these experiments are <em>inconsistent</em> with the widespread claim that phonological codes are computed automatically. Chapter 2 begins by reconsidering the utility of ?automaticity? as an explanatory framework. It is argued that automaticity should be replaced by accounts that make more specific claims about how processing unfolds. Experiment 5 yielded underadditivity of long-lag word repetition priming with decreasing SOA, suggesting that an early component of the lexical contribution to phonology does not use central attention. There was no evidence of Task 1 slowing with decreasing SOA in Experiments 6 and 7, suggesting that phonological recoding processes are postponed until central attention becomes available. Theoretical development in this field (and others) will be facilitated by abandoning the idea that skilled performance inevitably means that all the underlying processes are automatic.

Three experiments examine how collaboration influences visual search performance. Working with a partner or on their own, participants reported whether a target was present or absent in briefly presented search displays. The search performance of individuals working together (collaborative pairs) was compared to the pooled responses of the individuals working alone (nominal pairs). Collaborative pairs were less likely than nominal pairs to correctly detect a target and they were less likely to make false alarms. Signal detection analyses revealed that collaborative pairs were more sensitive to the presence of the target and had a more conservative response bias than the nominal pairs. This pattern was observed when the search difficulty was increased and when the presence of another individual was matched across pairs. The results are discussed in the context of task sharing, social loafing and current theories of visual search.

The purpose of the thesis was to explore what students within vocational education are expected to learn and the practices that constitute vocational education in Swedish upper secondary school. The empirical basis for the thesis is two studies, both of which have been reported separately. In the first study, twelve vocational teachers were interviewed sequentially. Classroom observations were made of the tasks their students worked with and these supplemented the interviews. The second study consists of case studies of five teachers in academic subjects within vocational education. Here sequential interviews of the teachers and classroom observations of the tasks their students worked with were supplemented with group interviews of their students and, in two cases, of collaborating vocational teachers. A social perspective on knowing and learning was used for analysing data. The results from the interviews with the vocational teachers show that what they wanted their students to learn in vocational education (their object) is related to vocational knowing but is not the same thing. Knowing in school can be regarded as preparation for work within the respective vocational area, as preparation for further learning and as preparation for citizenship. The first category relates to vocational knowing, whereas the latter two relate to a broader commission of education in late modernity – the risk and uncertainty of the future work situation that the students are likely to encounter. The tasks were analysed regarding their content, form, and the tools used for completing the tasks. Three categories of tasks were construed: school tasks, simulated tasks and vocational tasks. School tasks are characterised by that they employ the practice of school, whereas the vocational tasks employ the practice of the respective vocation. Simulated tasks are specific in that they allow a testing and correction of the result before the job is done. Through school tasks the students were introduced into a new content. Vocational tasks were used in bridging school and work. Besides the obvious tools of the respective vocation, texts were also used as tools in the work with the tasks. Most texts were vocational texts, i.e. texts that were used in similar ways in school as within the vocation. The second study, case studies of five teachers in academic subjects within vocational education, focused the infused tasks their students worked with. These results showed that the teachers used three different steering documents for planning their work: the national curriculum for upper secondary school, the objectives of the respective programme, and the syllabuses for their subject. By using all three documents, they were able to construct infused tasks. These tasks made it possible for the students to see other aspects of their respective vocational area than within the vocational subjects, e.g. the environmental work, historical aspects etc. The texts the academic teachers used were not the same as those used by vocational teachers. These texts were texts ‘imposed by others’ (e.g. local authorities) but also used for work within the vocation. The ‘theorisation’ of vocational education, that has been claimed to be a consequence of the academic subjects, can be seen rather as a change within the vocations from an oral to a literate culture. In completing many of the tasks observed, theoretical knowledge from different domains, as well as skills were needed. Vocational education as a purely ‘practical’ education is therefore a myth. A variety of texts were used within vocational education for the work, mostly as tools. The literate practices of vocational education are similar to the literate practices of the vocations rather than to those of school. New tools seem to change working life and vocational education as well. This implies that a different kind of vocational knowing is needed. When employers control or simulate production processes instead of doing the manual work, vocational knowing becomes something else. This new kind of work is dependent on a different kind of experience. Thus the theorisation of the vocational education is a theorisation – or rather an abstraction – on many levels. Some of them have been developed within the vocations, others are imposed from the outside. Three social practices, vocational education, working life and academic education, formally have a joint responsibility for the vocational education. Depending on if and to what extent they collaborate, the learning practices offered to the students will differ. With collaboration, as in these two studies, the students encounter learning practices where the content from each of the three contexts can be experienced as reembedded into new contexts. / <p>Därtill 4 uppsatser</p>

Autism spectrum disorders (ASDs) are primarily defined by problems with social interaction and communication, but they are also associated with a complex cognitive profile. One area of difficulty for children and adults with ASD is problem-solving, or the process of identifying a solution to a puzzle or question where the answer is hidden. This can be seen on the Twenty Questions Task (TQT), a commonly-used measure of verbal problem-solving and executive functioning. Children with autism are consistently less efficient than typically-developing children in their questioning on the task: for instance, rather than ask a general, category-based question (e.g. “Is it a living thing?”) they may ask about single items (“Is it the dog?”) or very restricted groupings (“Is it something you wear on your feet?”). This has previously been interpreted as an example of a concept formation deficit in autism, deriving from underlying difficulties with complex and integrative information processing. However, success in problemsolving relies on a number of cognitive and linguistic processes that may be impaired in ASD. This thesis attempts to identify which of these may better explain autistic problem-solving performance, using the TQT as a specific example. The first experiment presented here examines the role of executive functioning difficulties in this profile. The performance of 22 children with ASD and 21 age- and IQ-matched typically-developing (TD) children was compared on a version of the TQT adapted to assess planning skills prior to problem-solving and selective attention during the task. Compared to controls, ASD participants were less efficient in their planning of questions, although not all ASD participants had difficulty constructing a plan. No specific effects of selective attention were evident. The second and third experiments explore the importance of atypical language development to this profile, using the example of deafness. Experiment 2 compares the performance of deaf (n = 9) and hearing (n = 27) adults on the TQT, replicating prior evidence of less efficient problem-solving in deaf graduate students. Experiment 3 contrasts TQT performance in 13 deaf schoolchildren with the ASD and TD data acquired in experiment 1. Like ASD children, deaf children were less efficient in their questioning than TD participants, even when controlling for cognitive ability differences. Both autism and deafness are associated with delays in early language development, whereas Asperger Syndrome (AS) is not. To test whether language delay explains autistic problem-solving difficulties, experiment 4 compares TQT performance in 15 children with autism, 15 AS children and 15 age- and IQ- matched typically-developing controls. Participants with autism asked less efficient questions than both AS and TD participants, between whom no differences were observed. This suggests that the problem-solving profile in autism may be better explained as a consequence of atypical language development, rather than other aspects of information processing or executive dysfunction.

Spontaneous speech is replete with disfluencies: pauses, hesitations, restarts, and less than ideal deliveries of information. Disfluency is a topic of interdisciplinary research with insights from psycholinguistics, phonetics and speech technology. Researchers have tried to determine: When does disfluency occur?, Can disfluency be reliably predicted to occur?, and ultimately, Why does disfluency occur? The focus of my thesis will be to address the question of why disfluency occurs by reporting the results of analyses of disfluency frequency and the relationship between disfluency and eye gaze in a collaborative dialogue. Psycholinguistic studies of disfluency and collaborative dialogue differ on their answers to why disfluency occurs and its role in dialogue. One hypothesis, which I will refer to as Strategic Modelling, suggests that disfluencies are designed by the speaker. According to the alternative view, which I will call the Cognitive Burden View, disfluency is the result of an overburdened language production system. Throughout this thesis, I will contrast these two theories for an ultimate answer to why disfluency occurs. Each hypothesis attaches a functional role to a structural definition of disfluency and therefore in order to determine why disfluency occurs, I will contrast the structural and functional characteristics of disfluency. I will attempt to do this by analysing the dialogue behaviour in terms of speech goals and eye gaze behaviour a speaker is engaged in when they make certain types of disfluencies. A multi-modal Map Task paradigm was used in this thesis, in which speakers were asked to describe the route on a cartoon map to a distant confederate listener who provided either visual or verbal feedback. Speakers were eye-tracked during the dialogue and a record was kept of when the speaker attended to the listener’s visual feedback. Experiment 1 tested the visual feedback paradigm to establish its validity as a baseline condition. Speakers were found to make more disfluencies when they could interact with the visual feedback, suggesting disfluency is more common in interactive circumstances. Experiment 2 added verbal feedback to the experimental paradigm to test whether listeners react differently to the two modalities of feedback. Speakers made more disfluencies when the feedback was more complicated. Structural disfluency types were also observed to fulfil different functions. Finally, Experiment 3 manipulated the motivation of the speaker and found that Motivated speakers gazed more often and were more disfluent per opportunity than Control speakers suggesting that highly motivated subjects are more willing to engage in difficult tasks.

Ellipsis is a phenomenon whereby constituents which are normally obligatory in the grammar are omitted in actual discourse. It is found in all types of discourse, from everyday conversation to poetry. The omitted constituents can range from one word to an entire clause, and recovery of the ellipted item depends sometimes on the linguistic and sometimes on the non-linguistic context. From a practical point of view, the contribution of ellipsis in the context is twofold. First, it is one of several important means of achieving cohesion in a text. Secondly, ellipsis contributes to communicative appropriateness determined by the type of linguistic activity (e.g., narrative, casual conversation), the mode of communication (e.g., written / spoken) and the relationship between participants. The aim of this research is to provide a description of the functions of elliptical utterances – textual and interpersonal – in English and Japanese, based on a cross-linguistic analysis of dialogues in the English and Japanese map task corpora. In order to analyse ellipsis in relation to its two key functions, elliptical clauses in the map task dialogues were examined. I discuss how ellipsis is used to realise cohesion in the map task dialogues. The findings challenge the well-known claim that topics are established by full noun phrases, which are subsequently realised by pronouns (English) and null pronouns (Japanese). Rather, the results suggest that full noun phrases are used for topic continuity in both languages. Constituents which are ellipted in an utterance are identified and related to the moves types which the utterance realises within the exchange structure. The ellipted elements will be categorised according to the constituent types (Subject, Finite, Predicator, Complement and Adjunct), using the systemic functional approach. This analysis reveals that whereas in the English dialogues the most common types of ellipsis are that of Subject and Finite elements, in the Japanese dialogues the most common type is that of Subject. Types of ellipsis are also correlated with speech acts in the dialogues. The relation between types of ellipsis and particular speech acts associated with them is strikingly similar in the English and Japanese dialogues, despite the notable difference in grammar and pragmatics between the two languages. This analysis also shows how these types of ellipsis are associated with interpersonal effects in particular speech acts: ellipsis of Subject and Finite can contribute to a sharp contrast in the question and answer sequence, while Subject ellipsis in Japanese can contribute to modifying the command-like force in giving instructions. These effects can be summed up as epistemic and deontic modality respectively. Ultimately, it is argued that some types of ellipsis can serve as modality expressions. Additionally, in comparison to the way of realising the speech act of giving instructions in the English dialogues, it emerges that the Japanese speakers exploit ellipsis, which seems to be associated with lowering the degree of the speaker’s commitment to the proposition. As implications for pedagogical settings, I present pedagogical descriptions of ellipsis for Japanese learners of English and English learners of Japanese. Since the description is for specific learners, the approach which takes the difference in grammar and pragmatics between the two languages is made possible. Although descriptions state some detailed facts of ellipsis in English and Japanese, primarily highlighted is the importance of raising awareness of elliptical forms for particular functions in particular contexts. As ellipsis is a product of forms, functions and contexts, it is a most remarkable feature of spoken language. Spoken language is claimed by some researchers to show similar linguistic features among languages because of the restrictions inherent in the medium on communication. In the form of pedagogical description, I show the similarities and differences in ellipsis which derive from the grammar and pragmatics of each language, which are observed in the preceding linguistic research. Through the presentation of the findings which are modified for learners, learners will know how languages show convergence and divergence cross-linguistically.

In the Storyline approach a fictive world is created in the classroom. Learners become characters in a story, which develops as they work in small groups on open key questions, devised by the teacher on the basis of curriculum content and in which practical and theoretical tasks are integrated. Though established in first language contexts, Storyline is less known in second language education, although it would seem to offer conditions considered to promote language development in young learners: the story framework provides an engaging and meaningful context in which learners use their language skills holistically, in tasks which simulate the way they might use English in the real world, and in which they can use their creative talents. This multi-strategy case study investigated the language development of a class of Swedish 11-13 year olds who took part in Storyline, Our Sustainable Street, lasting five weeks. In the topic the learners were families living in a new street in a fictive English town. The aim was to consolidate their existing structural and lexical knowledge, develop their language skills and introduce the lexis of sustainability. Findings show that the learners became engaged when they worked with the Storyline, and that this impacted positively on their language development, especially regarding the learning of new words, losing the fear of speaking English before their peers, and in the voluntary production of longer and more structurally and lexically complex written texts. Features which contributed most to learner engagement were found to be group work, art work and the variety of task types, with the boys also motivated by not working with a textbook and girls by opportunities to use their imagination. The results suggest that inclusion of the Storyline approach in a teaching repertoire can facilitate language development in young learners.

The topic of this thesis is cognitive control: how the brain organises itself to perform the many tasks it is capable of and how it switches flexibly among them. Task-switching experiments reveal a substantial cost in reaction time and accuracy after a switch in tasks. This "switch cost" is reduced by preparation (suggesting anticipatory task-set reconfiguration), but not eliminated. The thesis focuses on the sources of the "residual" cost. Most accounts attribute it to response selection being prolonged on a task-switch trial by task conflict, e.g. by 'task-set inertia' — persisting activation/inhibition of the previous task's S-R rules — or their associative reactivation by the stimulus. Four experiments used event-related potentials (ERPs) to determine which stages of task processing are influenced by a change in tasks, looking for delays in process-specific markers in the ERP. Experiments 1 and 2 showed that a prepared switch to a reading task from a perceptual judgement delayed early ERP markers of lexical access by a large fraction of the RT switch cost, suggesting that a substantial part of the residual cost arises in processes earlier than response selection, possibly due to task-related attentional inertia. Markers of lexical access observed in the non-lexical task were larger on switch than repeat trials, providing the first electrophysiological evidence of task-set inertia. Experiment 3 examined the effects of an unprepared switch in the same way. ERP waveforms were modulated by a switch before markers of lexical access were evident, suggesting additional processing demands compete for resources with lexical access. A simple delay, however, was not found; post-stimulus task-set reconfiguration does not just insert an extra processing stage. Experiment 4 looked for a delay in the onset of an early ERP marker of emotional processing when the task switched between categorising facial expression and classifying a superimposed letter. No such delay was found in this case, and ERP markers of emotion processing were present to the same extent in the letter task. This suggests that, given appropriate spatial attention, processing facial emotion unfolds automatically, independent of attention allocation to the facial features. Experiments 5-7 further explored the link between conflict due to processing the irrelevant stimulus dimension and the ERP post-stimulus negativity that accompanies the residual cost. The negativity could be elicited even on trials of non-switching blocks by prior training on classifying the irrelevant attribute of the stimulus using the same responses. But this effect did not seem to result from the trained class of irrelevant attribute attracting more attention. Finally, Experiment 8 followed up an incidental observation in Experiment 1 to establish the novel observation that a task-switching context abolishes the usual ERP correlate of withholding a response in a go/no-go paradigm, suggesting an interesting interaction between task-set control and response inhibition.