Showing papers by "City University London published in 1997"

Ask for information retrieval: part I.: background and theory

Abstract: We report the results of a British Library Research and Development Department‐funded design study for an interactive information retrieval system which will determine structural representations of the anomalous states of knowledge (ASKs) underlying information needs, and attempt to resolve the anomalies through a variety of retrieval strategies performed on a database of documents represented in compatible structural formats. Part I discusses the background to the project and the theory underlying it, Part II (next issue) presents our methods, results and conclusions. Basic premises of the project were: that information needs are not in principle precisely specifiable; that it is possible to elicit problem statements from information system users from which representations of the ASK underlying the need can be derived; that there are classes of ASKs; and, that all elements of information retrieval systems ought to be based on the user's ASK. We have developed a relatively freeform interview technique for eliciting problem statements, and a statistical word co‐occurrence analysis for deriving network representations of the problem statements and abstracts. Structural characteristics of the representations have been used to determine classes of ASKs, and both ASK and information structures have been evaluated by, respectively, users and authors. Some results are: that interviewing appears to be a satisfactory technique for eliciting problem statements from which ASKs can be determined; that the statistical analysis produces structures which are generally appropriate both for documents and problem statements; that ASKs thus represented can be usefully classified according to their structural characteristics; and, that of thirty‐five subjects, only two had ASKs for which traditional ‘best match’ retrieval would be intuitively appropriate. The results of the design study indicate that at least some of our premises are reasonable, and that an ASK‐based information retrieval system is at least feasible.

Antenatal screening for Down's syndrome

Abstract: Background In 1968 the first antenatal diagnosis of Down's syndrome was made and screening on the basis of selecting women of advanced maternal age for amniocentesis was gradually introduced into medical practice. In 1983 it was shown that low maternal serum alpha fetoprotein (AFP) was associated with Down's syndrome. Later, raised maternal serum human chorionic gonadotrophin (hCG), and low unconjugated oestriol (uE3) were found to be markers of Down's syndrome. In 1988 the three biochemical markers were used together with maternal age as a method of screening, and this has been widely adopted. PRINCIPLES OF ANTENATAL SCREENING FOR DOWN'S SYNDROME: Methods of screening need to be fully evaluated before being introduced into routine clinical practice. This included choosing markers for which there is sufficient scientific evidence of efficacy, quantifying performance in terms of detection and false positive rates, and establishing methods of monitoring performance. Screening needs to be provided as an integrated service, coordinating and managing the separate aspects of the screening process. SERUM MARKERS AT 15-22 WEEKS OF PREGNANCY: A large number of serum markers have been found to be associated with Down's syndrome between 15 and 22 weeks of pregnancy. The principal markers are AFP, hCG or its individual subunits (free alpha- and free beta-hCG), uE3, and inhibin A. Screening performance varies according to the choice of markers used and whether ultrasound is used to estimate gestational age (table 1). When an ultrasound scan is used to estimate gestational age the detection rate for a 5% false positive rate is estimated to be 59% using the double test (AFP and hCG), 69% using the triple test (AFP, hCG, uE3), and 76% using the quadruple test (AFP, hCG, uE3, inhibin A), all in combination with maternal age. Other factors that can usefully be taken into account in screening are maternal weight, the presence of insulin dependent diabetes mellitus, multiple pregnancy, ethnic origin, previous Down's syndrome pregnancy, and whether the test is the first one in a pregnancy or a repeat. Factors such as parity and smoking are associated with one or more of the serum markers, but the effect is too small to justify adjusting for these factors in interpreting a screening test. Urinary markers and fetal cells in maternal blood Urinary beta-core hCG has been investigated in a number of studies and shown to be raised in pregnancies with Down's syndrome. This area is currently the subject of active research and the use of urine in future screening programmes may be a practical possibility. Other urinary markers, such as total oestriol and free beta-hCG may also be of value. Fetal cells can be identified in the maternal circulation and techniques such as fluorescent in situ hybridisation can be used to identify aneuploidies, including Down's syndrome and trisomy 18. This approach may, in the future, be of value in screening or diagnosis. Currently, the techniques available do not have the performance, simplicity, or economy needed to replace existing methods. Demonstration projects Demonstration projects are valuable in determining the feasibility of screening and in refining the practical application of screening. They are of less value in determining the performance of different screening methods. Several demonstration projects have been conducted using the triple and double tests. In general, the uptake of screening was about 80%. The screen positive rates were about 5-6%. About 80% of women with positive screening results had an invasive diagnostic test, and of those found to have a pregnancy with Down's syndrome, about 90% chose to have a termination of pregnancy. ULTRASOUND MARKERS AT 15-22 WEEKS OF PREGNANCY: There are a number of ultrasound markers of Down's syndrome at 15-22 weeks, including nuchal fold thickness, cardiac abnormalities, duodenal atresia, femur length, humerus length, pyelectasis, and hyperechogenic bowel. (ABSTRA

Children Raised in Fatherless Families from Infancy: Family Relationships and the Socioemotional Development of Children of Lesbian and Single Heterosexual Mothers

Abstract: The aim of the study was to investigate family functioning and the psychological development of children raised in fatherless families from their first year of life. Thirty lesbian mother families and 42 families headed by a single heterosexual mother were compared with 41 two-parent heterosexual families using standardised interview and questionnaire measures of the quality of parenting and the socioemotional development of the child. The results show that children raised in fatherless families from infancy experienced greater warmth and interaction with their mother, and were more securely attached to her, although they perceived themselves to be less cognitively and physically competent than their peers from father-present families. No differences were identified between families headed by lesbian and single heterosexual mothers, except for greater mother-child interaction in lesbian mother families.

Application of evolutionary programming to reactive power planning-comparison with nonlinear programming approach

Abstract: This paper proposes an application of evolutionary programming (EP) to reactive power planning (RPP). Several techniques have been developed to make EP practicable to solve a real power system problem and other practical problems. The proposed approach has been used in the IEEE 30-bus system and a practical power system. For illustration purposes, only results for the IEEE 30-bus system are given. Simulation results, compared with those obtained by using a conventional gradient-based optimization method, Broyden's method, are presented to show that the present method is better for power system planning. In the case of optimization of noncontinuous and nonsmooth functions, EP is much better than nonlinear programming. The comprehensive simulation results show a great potential for applications of EP in power system economical and secure operation, planning and reliability assessment.

Investigation into the increase in hay fever and eczema at age 16 observed between the 1958 and 1970 British birth cohorts.

Abstract: OBJECTIVE: To investigate whether changes in certain perinatal and social factors explain the increased prevalence of hay fever and eczema among British adolescents between 1974 and 1986. DESIGN: Two prospective birth cohort studies. SETTING: England, Wales, and Scotland. SUBJECTS: 11,195 children born 3-9 March 1958 and 9387 born 5-11 April 1970. MAIN OUTCOME MEASURES: Parental reports of eczematous rashes and of hay fever or allergic rhinitis in the previous 12 months at age 16. RESULTS: The prevalence of the conditions over the 12 month period increased between 1974 and 1986 from 3.1% to 6.4% (prevalence ratio 2.04 (95% confidence interval 1.79 to 2.32)) for eczema and from 12.0% to 23.3% (prevalence ratio 1.93 (1.82 to 2.06)) for hay fever. Both conditions were more commonly reported among children of higher birth order and those who were breast fed for longer than 1 month. Eczema was more commonly reported among girls and hay fever among boys. The prevalence of hay fever decreased sharply between social classes I and V, increased with maternal age up to the early 30s, and was lower in children whose mothers smoked during pregnancy. Neither condition varied significantly with birth weight. When adjusted for these factors, the relative odds of hay fever (1986 v 1974) increased from 2.23 (2.05 to 2.43) to 2.40 (2.19 to 2.63). Similarly, the relative odds of eczema rose from 2.02 (1.73 to 2.36) to 2.14 (1.81 to 2.52). CONCLUSIONS: Taken together, changes between cohorts in sex, birth weight, birth order, maternal age, breast feeding, maternal smoking during pregnancy, and father's social class at birth did not seem to explain any of the observed rise in the prevalence of hay fever and eczema. However, correlates of these factors which have changed over time may still underlie recent increases in allergic disease.

The West of Scotland coronary prevention study: economic benefit analysis of primary prevention with pravastatin

Abstract: OBJECTIVE: To estimate the economic efficiency of using pravastatin to prevent the transition from health to cardiovascular disease in men with hypercholesterolaemia. DESIGN: Economic benefit analysis based on data from the West of Scotland coronary prevention study. Treatment specific hazards of developing cardiovascular disease according to various definitions were estimated. Scottish record linkage data provided disease specific survival. Cost estimates were based on extracontractual tariffs and event specific average lengths of stay calculated from the West of Scotland coronary prevention study. SUBJECTS: Men with hypercholesterolaemia similar to the subjects in the West of Scotland coronary prevention study. MAIN OUTCOME: Cost consequences, the number of transitions from health to cardiovascular disease prevented, the number needed to start treatment, and cost per life year gained. RESULTS: If 10,000 of these men started taking pravastatin, 318 of them would not make the transition from health to cardiovascular disease (number needed to treat, 31.4), at a net discounted cost of 20m Pounds over 5 years. These benefits imply an undiscounted gain of 2,460 years of life, and thus 8121 Pounds per life year gained, or 20,375 Pounds per life year gained if benefits are discounted. Restriction to the 40% of men at highest risk reduces the number needed to treat to 22.5 (5601 Pounds per life year gained (undiscounted) and 13,995 Pounds per life year gained (discounted)). CONCLUSIONS: In subjects without evidence of prior myocardial infarction but who have hypercholesterolaemia, the use of pravastatin yields substantial health benefits at a cost that is not prohibitive overall and can be quite efficient in selected high risk subgroups.

The measurement of local axial strains in triaxial tests using lvdts

Abstract: In this Technical Note, the author describes an experiment in the use of Linear Variable Differential Transformer (LVDT), to allow accurate measurement of axial displacement over the complete range of strains of interest to geotechnical engineers.

Some conservative stopping rules for the operational testing of safety critical software

Abstract: Operational testing, which aims to generate sequences of test cases with the same statistical properties as those that would be experienced in real operational use, can be used to obtain quantitative measures of the reliability of software. In the case of safety critical software it is common to demand that all known faults are removed. This means that if there is a failure during the operational testing, the offending fault must be identified and removed. Thus an operational test for safety critical software takes the form of a specified number of test cases (or a specified period of working) that must be executed failure-free. This paper addresses the problem of specifying the numbers of test cases (or time periods) required for a test, when the previous test has terminated as a result of a failure. It has been proposed that, after the obligatory fix of the offending fault, the software should be treated as if it were completely novel, and be required to pass exactly the same test as originally specified. The reasoning here claims to be conservative, in as much as no credit is given for any previous failure-free operation prior to the failure that terminated the test. We show that, in fact, this is not a conservative approach in all cases, and propose instead some new Bayesian stopping rules. We show that the degree of conservatism in stopping rules depends upon the precise way in which the reliability requirement is expressed. We define a particular form of conservatism that seems desirable on intuitive grounds, and show that the stopping rules that exhibit this conservatism are also precisely the ones that seem preferable on other grounds.

Designing effective multimedia presentations

Abstract: The paper reports four studies concerning attention to and comprehension of Multimedia presentations. The Multimedia sequence used was taken from a commercially produced CD-ROM, ‘The Etiology of Cancer’, First, an eye tracking study of the presentation is reported. A second study was then conducted on the recall of the materials used in the eye tracking study. The results of these studies were used to propose design guidelines for Multimedia presentations. The guidelines were applied to produce areauthored version of the original presentation. A further two studies were then conducted on the re-authored version to assess the impact of the design guidelines.

Ringing of a vertical cylinder in waves

Abstract: This paper analyses the results of two series of experiments concerned with the response of a single vertical cylinder in the inertia regime in steep non-breaking waves. We recorded first the loading on a cylinder when it was held stationary, and secondly, its response in the same waves when it was pivoted just above the floor of the wave flume, and supported at the top by springs in the horizontal plane. Spring stiffnesses were set to achieve natural frequencies (measured in still water) in the range between 3 and 11 times the dominant wave frequency. The experiments were repeated with cylinders of three different diameters. Peak loading on stationary cylinders was found to exceed the predictions of a Morison model (based on kinematics computed from a numerical model of the measured waves), though improvements were achieved through the inclusion of slender-body terms. Measured ringing responses are generally in good agreement with those computed on a quasi-static basis from the measured loading history, but in some conditions, particularly at low frequency ratios, there is clearly some feedback from the motion to the excitation. Peak accelerations in the steepest waves are found to be limited approximately to those that would occur if the maximum loading were applied as a step change. Particular attention is given to a rapid cycle of loading that occurs after the crest has passed the cylinder's axis, and to images of the flow around the cylinder at the water surface.

Extended requirements traceability: results of an industrial case study

Abstract: Contribution structures offer a way to model the network of people who have participated in the requirements engineering process. They further provide the opportunity to extend conventional forms of artifact-based requirements traceability with the traceability of contributing personnel. We describe a case study that investigated the modelling and use of contribution structures in an industrial project. In particular, we demonstrate how they made it possible to answer previously unanswerable questions about the human source(s) of requirements. In so doing, we argue that this information addresses problems currently attributed to inadequate requirements traceability.

Tight-binding theory of tunneling giant magnetoresistance

Abstract: A unified theory of the tunneling magnetoresistance (TMR) and of the ballistic-current perpendicular-to-plane giant magnetoresistance (CPP GMR) is developed. It is based on the Kubo-Landauer formula and fully realistic tight-binding bands fitted to an ab initio band structure. The theory is first applied to a single-orbital tight-binding model to investigate analytically a continuous transition from the CPP GMR of a metallic system to the TMR of a tunneling junction. The transition takes place when either hopping of electrons between the ferromagnetic electrodes is gradually turned off or the on-site potentials in the nonmagnetic spacer are varied so that the Fermi level in the spacer moves into the band gap. It is shown that the TMR approaches rapidly the same saturation value when either the interelectrode hopping decreases or the height of the insulating barrier increases. When the insulating barrier is high (band gap is large), the TMR depends only weakly on the thickness of the insulating layer. However, when the band gap is small compared to the conduction band width, the TMR decreases rapidly with increasing thickness of the insulator. The numerical results for a Co(001) junction, based on a fully realistic band structure of the Co electrodes, show a very similar behavior. As the tight-binding hopping matrix between the Co electrodes is gradually turned off, the TMR ratio drops initially very rapidly from its value of 280% in the metallic regime to about 40% but then stabilizes in the range 40--65%. This is in a very good agreement with the observed value of 40%. The polarization of the current flowing across the Co junction in the metallic regime is negative (antiparallel to the magnetization) but becomes positive in the tunneling regime. The sign of the calculated polarization is, therefore, in agreement with the sign observed in all the experiments on tunneling from transition-metal ferromagnets.

Modern Actuarial Theory and Practice

Abstract: INVESTMENT Investments and Valuation General Principles of Asset Allocation Asset Allocation for Institutional Investors The Selection of Investment Portfolios: Mathematical Techniques Stochastic Investment Modeling and the Measurement of Investment Risk Life Insurance Fundamental Features of Life Insurance Non-Participating Life Insurance Participating Life Insurance The Regulation of Solvency and its Effect on the Emergence of Profit Life Office Risks and Risk Management The Actuarial Role in the Management of Life Office Risk GENERAL INSURANCE Introduction to General Insurance General Insurance Accounts Premium Rating Reinsurance Reserving General Insurance Accounts Pensions Pension Scheme Benefits Investment Policy Actuarial Basis Meeting the Cost Actuarial Investigations ACTUARIAL MODELS An Introduction Time Delays and the Underwriting Cycle Stochastic Approach to Life Insurance Mathematics Pension Funding Models and Feedback Multiple state Models and Disability Insurance

Designing Virtual Environments for Usability

Abstract: The development of HCI guidelines for virtual environments, is reported, using interaction modelling

Conceptual combination: Conjunction and negation of natural concepts

Abstract: The operation of negation on combinations of natural categories was examined in two experiments. In the first, category membership ratings of lists of items were obtained for pairs of concepts considered individually and in two logical combinations: conjunctions (e.g., “Tools which are also Weapons”) and negated conjunctions—forms of those conjunctions in which the modifier noun category was negated (“Tools which arenot Weapons”). For conjunctions, results supported earlier findings of overextension and the geometric averaging of constituent membership values (Hampton, 1988b). Previous findings of concept dominance and noncommutativity within conjunctions were also replicated, both for typicality ratings and for probability of class membership. For negated conjunctions, the pattern of dominance was similar but interacted with order within the conjunction. Negated conjunctions were also overextended. The second experiment explored how the attributes of negated conjunctions were derived from those of the two component concepts. Frequency of generation of attributes expressed positively (has wheels) or negatively (has no wheels) followed rated frequency in the negated category. The distinctiveness of an attribute to distinguish the complement from the head-noun class was associated with the generation of attributes, particularly when there was relatively high overlap between the two categories.

Numeracy and employment

Abstract: Uses National Child Development Study (NCDS) data to examine the employment experiences of men and women assessed with poor numeracy compared with those with good numeracy skills at age 37. To uncover the extent of negative effects of having poor numeracy skills, the sample is restricted to those whose poor or good numeracy was accompanied by good literacy skills. As a further control, much of the analysis is also restricted to those who had left full‐time education at age 16. Maps the proportions in full‐time employment between ages 17 to 37 and demonstrates the very different labour market experiences of the two skills groups in the areas of occupation, training, promotion and income. Concludes that poor numeracy reduces employment opportunities and progress in jobs.

On Reporting Recollective Experiences and “Direct Access to Memory Systems”

Abstract: Strack and Forster (1995) showed that, unlike remember responses, know responses in recognition memory were influenced by manipulating response bias. We describe an experiment that replicated theirs but additionally allowed subjects to report guesses. Only guess responses were influenced by this manipulation. Response bias had no effects on either know or remember responses. This outcome suggests that manipulating response bias influences know responses only when guessing is encouraged but not reported as such. Moreover, though know responses reflected memory for the study events, guess responses did not.

A technique combination approach to requirements engineering

Abstract: An approach to requirements engineering based on a combination of early prototyping, scenario-based analysis and design rationale is described. Requirements are elicited by presenting users with a prototype-simulation of a prospective design, combined with rationale based techniques for structuring probe questions. Design of analysis sessions and a walkthrough method for requirements elicitation are reported in three layers for linking questions to artefact/scenario demonstrations, follow-up questioning for user-system dependencies and handling user-analyst discourse. An empirical study of the requirements analysis approach is reported. The study used a ship board emergency application. The technique combination approach proved very effective in eliciting requirements but differences in analyst style were an important variable. Recommendations are made for designing and managing requirements capture sessions using scenario-based approaches.

Development and Optimization of Screw Machines With a Simulation Model—Part II: Thermodynamic Performance Simulation and Design Optimization

Abstract: This paper presents a method for the design of twin screw compressors and expanders, which is based on a differential algorithm for defining the rotor profile and an analytical model of the fluid flow and thermodynamic processes within the machine. Part I of the paper presents a method for screw rotor profile generation which simplifies and improves design procedures. An example is given of its use in the development of a new N rotor profile, which is shown to be superior to other well-known types. Part II describes a numerical model of the thermodynamic and fluid flow processes within screw machines, which is valid for both the compressor and expander modes of operation. It includes the use of the equations of conservation of mass and energy applied to an instantaneous control volume of trapped fluid within the machine with allowance for fluid leakage, oil or other fluid injection, heat transfer, and the assumption of real fluid properties. By simultaneous solution of these equations, pressure-volume diagrams may be derived of the entire compression or expansion process within the machine. The procedure has been developed over a period of fifteen years and validated with experimental results obtained from both reciprocating and screw compressors and screw expanders, some of which are included. The rotor profile generation processor, thermofluid solver and optimizer, together with preprocessing facilities for the input data and graphical post-processing and CAD interface, have been incorporated into a design package which provided a suitable tool for analysis and optimization of twin screw machine design. An example of its use is given in the optimization of the gate tip radius of a selected compressor design.

Learning from practice? Mental health nurses' perceptions and experiences of clinical supervision.

Abstract: In recent years nursing as a whole has moved from a position of apparently little manifest concern in the issue of 'clinical supervision' to a veritable explosion of interest which is beginning to find expression in the literature. Beginning with a discussion of clinical supervision from within a psychodynamically informed interpersonal nursing framework this paper reports on a small scale qualitative inquiry which aimed to explore mental health nurses' perceptions and experiences of clinical supervision. Analysis of data derived from a series of semi-structured interviews provides very encouraging early indications that mental health nurses are becoming better able to reflect upon the nature of their own formative learning needs and so to take seriously their need for professional support as they strive towards a more therapeutic relationship with their patients. However, whilst all of the participants in the study had a positive perception of the potential value of clinical supervision, there is clear evidence to suggest that their actual experience was that 'good enough supervision' was more the exception than the rule. The participants' perceptions and experiences are described and the implications for research, practice, education and the management of service delivery systems are outlined.

Wealth creation and bid resistance in u.k. takeover bids

Abstract: In this paper we investigate the determinants of, and relationship between, wealth creation and bid resistance for a sample of 178 successful takeover bids in the U.K. Within the context of an event study approach we test a range of hypotheses against a background that recognizes the existence of agency conflict and the role of corporate governance mechanisms designed to mitigate its effect. The results obtained are interpreted within the context of the U.K. corporate environment. We find that wealth creation and bid resistance are mutually dependent on each other. We find evidence suggesting the presence of managerial and financial synergy but the absence of operational synergy. Our results also suggest that there is some conflict between managers and shareholders but that significant monitoring is exercised by the particular governance mechanisms we investigate.

A small exploratory study of the reaction of older people to an episode of delirium.

Abstract: Delirium or an acute confusional state, occurs as a result of disease or physiological imbalance secondary to impaired brain function. One of its main clinical features is widespread cognitive impairment, which causes patients to become disconnected from their immediate surroundings and misinterpret reality. It has a sudden onset and its duration is relatively brief. Some authors take the view that delirium might be interpreted as a precursor to dementia. The aim of the study was to retrospectively explore older peoples' experience of an episode of delirium. In particular, whether they knew what had caused and cured it; and whether it had left them with any unresolved feelings of anxiety. A cross sectional design using grounded theory methodology was chosen, as being the most appropriate method for exploring this issue. A sample of 19 patients was selected using predetermined criteria, and engaged in a semi-structured interview with the researcher, in the ward environment. The interviews were audiotaped, transcribed, and analysed using the constant comparison method. Those interviewees who had illusions and hallucinations, were often able to describe their experiences in detail. They ranged from being pleasant and entertaining, to horrible and frightening. They were also able to remember short verbal commands from nurses during the episode of altered perception. Others remembered, or chose not to remember, very little. Few interviewees appeared to know exactly what had caused and cured the delirium, although some were able to tentatively connect the experience to their present medical condition. There also appeared to be little evidence of therapeutic communication with nursing staff once the episode of delirium had resolved. Although no one connected the experience with dementia, there did seem to be some evidence of mildly disturbed feelings, on reflecting back over the episode. As interviewees were generally willing to discuss their experiences with the researcher, it suggests that it would be helpful for nurses to provide opportunities to do so. Nevertheless, interviewees appeared to regard the episode simply as a transitory event in the overall context of illness, admission to hospital and their future welfare. The latter was of prime concern; yet again it appeared that they did not always receive the information they required to maintain control over their personal destinies.

Recognition memory with little or no remembering: Implications for a detection model

Abstract: Remembering and knowing are two states of awareness that reflect autonoetic and noetic consciousness. Recent extensions of signal detection theory have attempted to fitremember andknow responses, which measure these states of awareness, to a continuum of trace strength or familiarity. The model assumes there are two response criteria, a remembering criterion, which is more strict, and a recognition criterion, which is more lenient and leads to any positive recognition response. The most important prediction of this model is that bias-free estimates of memory should be the same whether derived from overall hit and false alarm rates or fromremember hit and false alarm rates. We describe evidence that disconfirms this prediction and discuss other findings that the model cannot accommodate.

The Short Term Inflation Hedging Characteristics of UK Real Estate

Abstract: This study investigates the short term inflation hedging characteristics of U.K. real estate compared to other U.K. investments. It considers not only total returns but also changes in income and changes in capital values. The analyses are undertaken using annual and quarterly data. Stocks, bonds, appraisal-based real estate (including the three property types separately) and real estate stocks are considered. Real estate series, constructed from the original appraisal series to take account of autocorrelation, are also used. The methodology is based on that devised by Fama and Schwert (1977) and tests are undertaken for stationarity and for structural breaks. Hypotheses are established about the coefficients on expected and unexpected inflation in the model and these are tested. It is concluded that real estate has poorer short term hedging characteristics for total return, change in capital value and change in income than stocks but better characteristics than bonds. However, there is evidence to suggest that the relationships change under different economic environments.

An impairment in processing verbs' thematic roles: A therapy study

Abstract: This paper describes a subject with a selective verb disorder. Verb retrieval was impaired both in spontaneous speech and naming. When verbs were accessed a striking dissociation emerged. Subcategorization was surprisingly intact, while the assignment of verbs' thematic roles was poor. Verb comprehension was also impaired, particularly when tasks demanded an appreciation of thematic information. A remediation programme was administered which aimed to improve insight into the role structures and mapping requirements of three argument verbs. Evaluation showed gains in the production of this type of verb, which generalized to untreated items. However, there was no generalization to verbs of a different type. Progress was also suggested by a second evaluative procedure, in which observers were asked to judge the intelligibility of the subject's output, before and after therapy. The theoretical implications of the findings are discussed.