Psychological sequelae of colonic resections.

AIM: The prevalence of anxiety, depression and post-traumatic stress disorder (PTSD) in the general population has been estimated to be 5.9%, 3.3% and 4.4% respectively. The aim of this study was to determine whether psychological problems are more prevalent following colorectal surgery. METHOD: Patients who had undergone colorectal resection in a 2-year period across four centres were asked to complete validated screening questionnaires for anxiety, depression and PTSD (GAD-7, PHQ-9, PCL-5) 12-48 months after surgery. Risk factors were identified using multiple linear regression analysis. RESULTS: After excluding those who had died or received palliative diagnoses, questionnaires were sent to 1150 patients. 371 responded (32.3% response rate); median age 67 (20-99) years; 51% were men. 58% of patients underwent surgery for cancer; 23% had emergency surgery. 28% of patients screened positive for at least one psychological condition, with 20% screening positive for anxiety, 22% for depression and 14% for PTSD. Patients who were younger, women, had surgery as an emergency, for benign conditions, had stomas and had critical care stay were more likely to have poorer psychological outcomes. Multiple linear regression found that only younger age (P = 0.000) and female gender (P = 0.048) were significant risk factors. CONCLUSION: The prevalence of anxiety, depression and PTSD appears to be high in patients who have undergone colorectal surgery. Younger patients and women are particularly at risk. Further work is needed to determine how best to prevent, detect and treat people with adverse psychological outcomes following colorectal surgery.

Inequalities in health? An update on the effect of social deprivation for patients with breast cancer in South East Wales.

BACKGROUND: Breast cancer, historically a disease of more affluent women, has increased in incidence for women from areas of greater social deprivation, yet prognosis is worse for these women. This study identifies differences in presentation, treatment and prognostic factors between the socioeconomic groups. METHODS: Patient data obtained from the prospectively maintained Welsh national Cancer Network Information System Cymru, for an 11-year period, were categorised according to Welsh Index of Multiple Deprivation quintiles. Quintiles were compared for differences in variables relating to patient characteristics, detection of cancer, tumour biology and treatment. RESULTS: 1570 patients were included. Analysis showed that in the more socially deprived quintiles, there are proportionally fewer women being diagnosed through the NHS breast cancer screening programme and as a consequence greater numbers of women from poorer areas being diagnosed outwith the screening age parameters. Screen detection is strongly associated with better prognosis in terms of Nottingham Prognostic Index. Similarly, increasing levels of social deprivation are associated with higher incidence of oestrogen receptor negative and triple negative tumours, both features associated with a shorter disease free and overall survival. Other variables of tumour biology, rates and type of surgical and adjuvant treatment were similar across social deprivation quintiles. CONCLUSION: There is a trend of reduced early detection of breast cancer in South East Wales in those patients living in areas of higher social deprivation. Given that there is equity in access to treatment within NHS, which is free for patients at the point of care, further study is warranted to address this existing disparity. Population cancer surveillance will need to inform both public health and NHS service responses, to continue to achieve improvements. Health trends may yet alter depending on current and future shifts in governmental health policy.

The Influence of Clinical and Patient-Reported Outcomes on Post-surgery Satisfaction in Cholecystectomy Patients.

BACKGROUND: Patient-reported outcomes (PROMs) and post-operative satisfaction have become a growing focus of surgical outcome evaluation and are considered key components of the movement towards patient-centred care. The aim was to compare the association of traditional clinical outcome measures and PROMs with post-surgery satisfaction in cholecystectomy patients. METHODS: Patients who had undergone elective or emergency cholecystectomy for gallstone disease were sent validated PROM questionnaires, and telephone follow-up was performed in all cases. Categorical data were compared with the Chi-square and Fisher's exact tests. Satisfaction was investigated using a "top-box" approach, and multivariable logistic regression was performed for factors significantly (p < 0.05) associated with satisfaction in univariable analyses. RESULTS: A total of 234 patients underwent cholecystectomy between 1 March 2014 and 1 May 2014, and 147 patients (63%) completed the questionnaire. 104/147 (71%) reported being "very satisfied" with their surgical outcome. In univariable analyses, satisfaction showed significant association with an absence of hospital-recorded 30-day complications (OR = 4.11, 95% CI 1.29-13.84), but not re-attendance, readmission, or length of stay. In a multiple regression analysis, no traditional clinical outcome measures were associated with satisfaction. By contrast, self-perceived health (OR = 4.04, 95% CI 1.44-11.86), the absence of patient-reported wound pain (OR = 6.11, 95% CI 1.83-21.74), and a return to normal leisure activities (OR = 11.14, 95% CI 2.61-55.26) were associated with satisfaction. CONCLUSION: PROMs are the major determinants of patient satisfaction following cholecystectomy. When assessing outcomes following cholecystectomy, the measurement of clinical outcomes alone is inadequate and should be supplemented by the use of PROMs.

Piperacillin/tazobactam-induced immune-mediated thrombocytopenia in the intensive care unit.

WHAT IS KNOWN AND OBJECTIVE: Drug-induced immune-mediated thrombocytopenia is a rare adverse event that remains a diagnostic challenge, especially in the critically ill population. There are only two previously reported cases of rapid and profound thrombocytopenia after administration of piperacillin/tazobactam. CASE SUMMARY: A 64-year-old man experienced several episodes of isolated thrombocytopenia after receiving piperacillin/tazobactam. Interestingly, the degree of thrombocytopenia varied with the amount of corticosteroid therapy the patient was receiving. Due to the complexity of thrombocytopenia in critically ill patients, other potential causes were extensively worked up and ruled out. WHAT IS NEW AND CONCLUSION: We describe the first case of piperacillin/tazobactam-induced immune-mediated thrombocytopenia that was mitigated by the administration of corticosteroid therapy. This case highlights the importance of identifying potential drug-related causes of isolated thrombocytopenia.

Prevalence of Toxoplasma gondii in localized populations of Apodemus sylvaticus is linked to population genotype not to population location.

Toxoplasma gondii is a globally distributed parasite infecting humans and warm-blooded animals. Although many surveys have been conducted for T. gondii infection in mammals, little is known about the detailed distribution in localized natural populations. In this study, host genotype and spatial location were investigated in relation to T. gondii infection. Wood mice (Apodemus sylvaticus) were collected from 4 sampling sites within a localized peri-aquatic woodland ecosystem. Mice were genotyped using standard A. sylvaticus microsatellite markers and T. gondii was detected using 4 specific PCR-based markers: SAG1, SAG2, SAG3 and GRA6 directly from infected tissue. Of 126 wood mice collected, 44 samples were positive giving an infection rate of 34.92% (95% CI: 27.14-43.59%). Juvenile, young adults and adults were infected at a similar prevalence, respectively, 7/17 (41.18%), 27/65 (41.54%) and 10/44 (22.72%) with no significant age-prevalence effect (P = 0.23). Results of genetic analysis of the mice showed that the collection consists of 4 genetically distinct populations. There was a significant difference in T. gondii prevalence in the different genotypically derived mouse populations (P = 0.035) but not between geographically defined populations (P = 0.29). These data point to either a host genetic/family influence on parasite infection or to parasite vertical transmission.

Knowledge and Perceptions of HPV and the HPV Vaccine among Pre-adolescent Girls and Their Guardians in Georgetown, Guyana.

OBJECTIVES: To examine the knowledge and perceptions of 11-year old girls and their guardians toward the human papillomavirus (HPV), HPV (mandatory) vaccination and cervical cancer and to determine their main sources of health information. METHODS: A cross-sectional study was done by interviewing two separate study populations ie 11-year old girls from five primary schools in Georgetown and their guardians. Questions were designed to assess level of knowledge as well as perceptions about mandatory vaccination and sources of health information. RESULTS: A total of 87 girls participated, of whom 10 (11%) had already received the HPV vaccine. Overall, when asked whether they knew of HPV, the HPV vaccine, cervical cancer or the Pap smear, more than half of the girls, in every instance, did not know. Seventy-four guardians took part and most (> 80%) of them claimed that they knew about these parameters except for HPV transmission (40%) and the cause of cervical cancer (30%). Both girls and guardians responded poorly to questions about the detection of cervical cancer. Furthermore, only two of the 14 girls who stated that they knew how HPV was transmitted, actually answered correctly that it was sexual transmission. Girls were almost twice as likely to be in favour of mandatory vaccination as guardians (OR 1.8, 95% CI: 0.9, 3.6) but the difference was not significant (p > 0.05). The girls indicated health centres/clinics (58%), whilst TV/radio (66%) was the preference for the guardians as their most popular health information sources. CONCLUSIONS: These findings point to a necessity for educational programmes and activities in which children and their guardians can meaningfully participate and be informed about the different aspects of HPV vaccination.

A molecular and ecological analysis of the trematode Plagiorchis elegans in the wood mouse Apodemus sylvaticus from a periaquatic ecosystem in the UK.

The prevalence of the digenean Plagiorchis sp. was investigated in a natural wood mouse population (Apodemus sylvaticus) in a periaquatic environment. Classical identification was complemented with the use of molecular differentiation to determine prevalence and verify species identity. Use of the complete ITS1-5.8S rDNA-ITS2 and partial 28S rDNA gene sequences have confirmed that the species reported at this location was Plagiorchis elegans and not Plagiorchis muris as reported previously. This underlines the difficulties in identification of these morphologically similar parasites. Plagiorchis elegans is typically a gastrointestinal parasite of avian species but has also been reported from small mammal populations. Although the occurrence of this digenean in A. sylvaticus in the UK is rare, in the area immediately surrounding Malham Tarn, Yorkshire, it had a high prevalence (23%) and a mean worm burden of 26.6 ± 61.5. The distribution of P. elegans followed a typically overdispersed pattern and both mouse age-group and sex were determined to be two main factors associated with prevalence. Male mice harboured the majority of worms, carrying 688 of 717 recovered during the study, and had a higher prevalence of 32.4% in comparison to only 8.7% in the small intestine of female mice. A higher prevalence of 43% was also observed in adult mice compared to 14% for young adults. No infection was observed in juvenile mice. These significant differences are likely to be due to differences in the foraging behaviour between the sexes and age cohorts of wood mice.

Identification of a new species of digenean Notocotylus malhamensis n. sp. (Digenea: Notocotylidae) from the bank vole (Myodes glareolus) and the field vole (Microtus agrestis).

Notocotylus malhamensis n. sp. is described from the caecum of the bank vole (Myodes glareolus) and the field vole (Microtus agrestis) from Malham Tarn Nature Reserve in North Yorkshire, UK. In total, 581 specimens were collected from rodents trapped at a wetland site (Tarn Fen) between July 2010 and October 2011 with a prevalence of 66·7% and mean intensity of 94·6 in the bank vole and 50% prevalence and a mean intensity of 4·3 in the field vole. This species appears to be most closely related to other previously described Notocotylus species infecting rodents in Europe but differs principally by the metraterm to cirrus sac ratio (1:1·5-1:1·2) in combination with a densely spinulated cirrus, simple caeca and a greater number of ventral glands in the lateral rows (14-17). The use of molecular differentiation was of limited use in this study due to a paucity of relevant information in the DNA sequence databases. However, the complete ITS1-5.8S rDNA-ITS2 and partial 28S gene sequences have been generated to provide a definitive tool for identification of this species in future studies. As far as we know this is the first report of a notocotylid infection in M. glareolus in the UK.

Prevalence and co-infection of Toxoplasma gondii and Neospora caninum in Apodemus sylvaticus in an area relatively free of cats.

The protozoan parasite Toxoplasma gondii is prevalent worldwide and can infect a remarkably wide range of hosts despite felids being the only definitive host. As cats play a major role in transmission to secondary mammalian hosts, the interaction between cats and these hosts should be a major factor determining final prevalence in the secondary host. This study investigates the prevalence of T. gondii in a natural population of Apodemus sylvaticus collected from an area with low cat density (<2·5 cats/km2). A surprisingly high prevalence of 40·78% (95% CI: 34·07%-47·79%) was observed despite this. A comparable level of prevalence was observed in a previously published study using the same approaches where a prevalence of 59% (95% CI: 50·13%-67·87%) was observed in a natural population of Mus domesticus from an area with high cat density (>500 cats/km2). Detection of infected foetuses from pregnant dams in both populations suggests that congenital transmission may enable persistence of infection in the absence of cats. The prevalences of the related parasite, Neospora caninum were found to be low in both populations (A. sylvaticus: 3·39% (95% CI: 0·12%-6·66%); M. domesticus: 3·08% (95% CI: 0·11%-6·05%)). These results suggest that cat density may have a lower than expected effect on final prevalence in these ecosystems.

The relation between atrial fibrillation wavefront characteristics and accessory pathway conduction.

Although the source-sink relationship for impulse propagation in cardiac tissues has been demonstrated in vitro, there has been no verification of this hypothesis in humans. Accordingly, eight patients undergoing surgical division of their accessory pathways were studied. A 56-channel (7 x 8) bipolar plaque electrode array was placed over the atrioventricular groove on the accessory pathway and atrial fibrillation electrically induced. 10 episodes of QRS transition from consecutively preexcited to nonpreexcited complexes were analyzed. This showed that consecutively preexcited QRS complexes were always associated with uniform large atrial wavefronts. Immediately prior to QRS transition, four general types of changes were observed: (a) premature invasion by secondary wavefronts creating local conduction block (n = 5); (b) wavefront collision leading to wavefront curvature (n = 2); (c) transition from a uniform large atrial wavefront to multiple fractionated small wavefronts (n = 1); and (d) uniform atrial wavefronts "marching" into the accessory pathway refractory period (n = 2). We conclude that local atrial wavefront characteristics are important factors influencing impulse propagation through the accessory pathway. The findings that local wavefront collision, curvature, or fractionation often precede loss of accessory pathway conduction support the notion that source-sink relationship is an important determinant of the safety factor for impulse propagation in the human heart.

Calibration of the microcalorimeter spectrometer on-board the Hitomi (Astro-H) observatory (invited).

The Hitomi Soft X-ray Spectrometer (SXS) was a pioneering non-dispersive imaging x-ray spectrometer with 5 eV FWHM energy resolution, consisting of an array of 36 silicon-thermistor microcalorimeters at the focus of a high-throughput soft x-ray telescope. The instrument enabled astrophysical plasma diagnostics in the 0.3-12 keV band. We introduce the SXS calibration strategy and corresponding ground calibration measurements that took place from 2012-2015, including both the characterization of the microcalorimeter array and measurements of the x-ray transmission of optical blocking filters.

Academic requirements for Certificate of Completion of Training in surgical training: Consensus recommendations from the Association of Surgeons in Training/National Research Collaborative Consensus Group.

BACKGROUND: Surgical trainees are expected to demonstrate academic achievement in order to obtain their certificate of completion of training (CCT). These standards are set by the Joint Committee on Surgical Training (JCST) and specialty advisory committees (SAC). The standards are not equivalent across all surgical specialties and recognise different achievements as evidence. They do not recognise changes in models of research and focus on outcomes rather than process. The Association of Surgeons in Training (ASiT) and National Research Collaborative (NRC) set out to develop progressive, consistent and flexible evidence set for academic requirements at CCT. METHODS: A modified-Delphi approach was used. An expert group consisting of representatives from the ASiT and the NRC undertook iterative review of a document proposing changes to requirements. This was circulated amongst wider stakeholders. After ten iterations, an open meeting was held to discuss these proposals. Voting on statements was performed using a 5-point Likert Scale. Each statement was voted on twice, with ≥80% of votes in agreement meaning the statement was approved. The results of this vote were used to propose core and optional academic requirements for CCT. RESULTS: Online discussion concluded after ten rounds. At the consensus meeting, statements were voted on by 25 delegates from across surgical specialties and training-grades. The group strongly favoured acquisition of 'Good Clinical Practice' training and research methodology training as CCT requirements. The group agreed that higher degrees, publications in any author position (including collaborative authorship), recruiting patients to a study or multicentre audit and presentation at a national or international meeting could be used as evidence for the purpose of CCT. The group agreed on two essential 'core' requirements (GCP and methodology training) and two of a menu of four 'additional' requirements (publication with any authorship position, presentation, recruitment of patients to a multicentre study and completion of a higher degree), which should be completed in order to attain CCT. CONCLUSION: This approach has engaged stakeholders to produce a progressive set of academic requirements for CCT, which are applicable across surgical specialties. Flexibility in requirements whilst retaining a high standard of evidence is desirable.

Automated tissue analysis--a bioinformatics perspective.

OBJECTIVES: Recent progress in automated tissue analysis (tissomics) provides reproducible phenotypical characterization of histological specimens. We introduce informatics tools to cluster and correlate quantitative tissue profiles with gene expression data. The great potential of synergies between tissue analysis and bioinformatics and its perspectives in medical research and computational diagnostics are discussed. METHODS: Key enablers in microscopic imaging and machine vision are reviewed to perform a high-throughput tissue analysis. Methodologies are described and results are demonstrated that support a combined analysis of tissue with gene expression profiles whereby the consideration of individual responses is key. RESULTS: Comprehensive histomorphometric profiles, extracted using machine vision, provide information regarding the components and heterogeneity of a tissue in a reproducible format amenable to data mining and analysis. Tissue quantitative information can be placed in synergetic context with bioinformatics data, such as gene expression profiles, for a more comprehensive stratification of individual responses. From a bioinformatics point of view tissue data are co-variants that support the identification of candidate genes relevant in tissue injury or disease. CONCLUSIONS: Progress in automated analytics enables the generation of quantitative data about tissue previously limited to visual histopathology. Such reproducible data sets can be statistically correlated and clustered throughout the continuum of bioinformatics. The combined approach supports a system-wide view of biology and has a potential to accelerate developments for a personalized computational diagnosis.

Antibiotic use in the nursing home. Physician practice patterns.

Antibiotic usage patterns were studied in two nonproprietary nursing homes that included 720 intermediate care and skilled nursing home beds. Medical records of residents receiving antibiotics were reviewed every fourth month for 1 year. Of 181 antibiotic prescriptions written for indications other than prophylaxis, 41% were for presumed urinary tract infections, 35% for respiratory tract infections, and 14% for skin/soft-tissue infections. The majority of antibiotic prescriptions (54%) were made by telephone order. Cultures were obtained in 60% of suspected infections; two thirds of cultures were of the urine. Antibiotics were changed during the course of therapy in only 12% of cases. Eighty-one percent of residents treated with antibiotics improved or were cured, 9.5% were hospitalized or died, and an additional 9.5% failed to improve but remained in the nursing home. Fever was present in 48% of cases prior to treatment, but had no predictive value for patient outcome. We conclude that antibiotic treatment in the nursing home is often initiated in the absence of fever, culture information, or examination of the patient. Empiric prescription of antibiotics in this setting generally is associated with favorable clinical course.

Visual categorical perception by rats with temporal, striate, or sham ablations.

Rats were trained to discriminate a 0 degrees stripe from a 90 degrees stripe in a two choice water maze. They were prepared with either Te2/3, partial striate (PS), or sham lesions and retrained on the preoperative discrimination. In two separate experiments, excellent savings was observed for all groups. Next, trials were administered with novel stripe orientations defined as either between- or within-category problems. Performance accuracy eroded rapidly for all groups in the first experiment, and no between-group differences were observed. In the second experiment, each session with categorical stimuli was preceded by four reminder trials with the original stimuli. This improved accuracy for all groups, but it was found that animals with PS lesions, not animals with T2/3 lesions, were impaired on between-category judgements. The impairment was not secondary to a disruption of basic visual sensory processing or significantly larger lesions relative to the Te2/3 group. As is the case for monkeys, accuracy with within-category stimuli was inferior to between-category stimuli for all groups. Possible reasons for this inter-species difference are discussed.

Patterns of avian seroprevalence to western equine encephalomyelitis and Saint Louis encephalitis viruses in California, USA.

Temporal and spatial changes in the enzootic activity of western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses were monitored at representative wetland study sites in the Coachella, San Joaquin, and Sacramento valleys of California from 1996 to 1998 using three methods: (1) virus isolation from pools of 50 host-seeking Culex tarsalis Coquillett females, (2) seroconversions in flocks of 10 sentinel chickens, and (3) seroprevalence in wild birds collected by mist nets and grain baited traps. Overall, 74 WEE and one SLE isolates were obtained from 222,455 Cx. tarsalis females tested in 4,988 pools. In addition, 133 and 40 seroconversions were detected in 28 chicken flocks, and 143 and 27 of 20,192 sera tested from 149 species of wild birds were positive for antibodies to WEE and SLE, respectively. WEE was active in all three valleys, whereas SLE only was detected in Coachella Valley. Seroconversions in sentinel chickens provided the most sensitive indication of enzootic activity and were correlated with seroprevalence rates in wild birds. Avian seroprevalence rates did not provide an early warning of pending enzootic activity in chickens, because positive sera from after hatching year birds collected during spring most probably were the result of infections acquired during the previous season. Few seroconversions were detected among banded recaptured birds collected during spring and early summer. Age and resident status, but not sex, were significant risk factors for wild bird infection, with the highest seroprevalence rates among after hatching year individuals of permanent resident species. Migrants (with the exception of mourning doves) and winter resident species rarely were positive. House finches, house sparrows, Gambel's quail, California quail, common ground doves, and mourning doves were most frequently positive for antibodies. The initial detection of enzootic activity each summer coincided closely with the appearance of hatching year birds of these species in our study areas, perhaps indicating their role in virus amplification. Bird species most frequently positive roosted or nested in elevated upland vegetation, sites where Cx. tarsalis host-seeking females hunt most frequently. These serosurveys provided important background information for planned host competence and chronic infection studies.

Evacuation behaviours of occupants with learning difficulties in residential homes.

PURPOSE: This paper reports the results of unannounced evacuation of two residential care premises providing accommodation for people with learning disabilities. METHOD: Awareness of disability has in relation to fire safety focussed generally on mobility. With the advent of performance-based fire safety engineering codes which require the characterization of buildings and their occupants it is necessary to obtain knowledge of the likely behaviours of people with learning difficulties in an emergency. The unannounced evacuations which were conducted at 11.30 pm were video recorded to enable observation and an analysis of the residents' behaviours. RESULTS AND CONCLUSION: The results and observations obtained raise many issues; including transferable training skills, predictability of evacuation behaviours, and the need in performance code evaluation to consider the characterization of buildings and their occupants as mutually inclusive processes.

Comparative effectiveness of three adult mosquito sampling methods in habitats representative of four different biomes of California.

The effectiveness of New Jersey (NJ) light, dry ice baited, and gravid female traps for collecting adult mosquitoes was compared at representative habitats in the Coachella, San Joaquin, and Sacramento valleys and the Los Angeles basin of California. The NJ light traps effectively sampled Anopheles freeborni, Culex tarsalis, Psorophora columbiae, and several Aedes when abundance was high in rural areas with minimal competitive illumination. Dry ice-baited encephalitis virus surveillance or CDC style traps collected significantly more females of most species at most localities than did NJ light traps, regardless of background illumination. The Cummings modification of the Reiter gravid female trap baited with a bulrush (Schoenoplectus) infusion was the best method for collecting Culex pipiens complex females in most habitats. In the Los Angeles basin, gravid traps baited with bulrush infusion collected, on average, 4.5 times more Culex quinquefasciatus females than did traps baited with the Reiter infusion. The bulrush infusion in combination with the Cummings trap design seemed to provide resting site cues and collected males as well as empty and bloodfed females. Mosquito surveillance programs in California should include the systematic operation of dry ice-baited and gravid female traps to improve surveillance sensitivity for selected species in appropriate habitats.

Comparison of dry ice-baited centers for disease control and New Jersey light traps for measuring mosquito abundance in California.

Mosquito catch in New Jersy light traps (NJLTs) has been declining in recent years, compromising the sensitivity of the California mosquito monitoring program. Centers for Disease Control traps (CDCTs) operated without light and augmented with dry ice have been considered for replacement or augmentation. To provide information on comparative sensitivity and ability to measure abundance over time and space, catch of mosquitoes in NJLTs was compared to catch in CDCTs operated concurrently at 8-10 sites within the Coachella Valley, Kern, San Joaquin County, and Sacramento-Yolo Mosquito and Vector Control Districts. The CDCTs always collected more female mosquitoes than did NJLTs; however, differences in sensitivity varied markedly over time and space precluding the calculation of a universal conversion factor. Regressions of the catch of female Culex tarsalis in CDCTs as a function of catch in NJLTs within districts indicated that the slopes varied markedly, again precluding the derivation of a universal function. Therefore, we recommend that mosquito surveillance programs replace or supplement NJLTs with systematically operated CDCTs to enhance sampling sensitivity for females of most mosquito species. However, both trap types should be operated concurrently at several sites within each district to derive regression functions to convert historical relative abundance data from NJLTs to equivalent counts in CDCTs for retrospective analyses.

Comparison of nonretarded and mentally retarded children on tasks involving direct and rule-governed imitation.

The influence of intellectual level and social reinforcement on imitation learning was examined. Tasks involving direct and rule-governed imitation of a mode were presented to 20 mentally retarded and 20 nonretarded children. The children within each group were randomly assigned to either an affective ("good-fine") or an informative ("correct-right") social reinforcement condition. Reinforcement, administered on a fixed ration (FR4) schedule, was contingent on the child's imitative behavior. A multivariate analysis of variance showed that both the Population X Reinforcement Type interaction and the Reinforcement main effect were significant. Univariate follow-up tests showed that only rule-governed imitation contributed significantly to the multivariate effects. Analysis of simple effects indicated that retarded children performed optimally under affective reinforcement, while the nonretarded children performed highest under informative reinforcement.