Beta-binomial meta-analysis of individual differences based on sample means and standard deviations: Studying reliability of sum scores of binary items.

Individual differences are studied with a multitude of test instruments. Meta-analysis of tests is useful to understand whether individual differences in certain populations can be detected with the help of a class of tests. A method for the quantitative meta-analytical evaluation of test instruments with dichotomous items is introduced. The method assumes beta-binomially distributed test scores, an assumption that has been demonstrated to be plausible in many settings. With this assumption, the method only requires sample means and standard deviations of sum scores (or equivalently means and standard deviations of percent-correct scores), in contrast to methods that use estimates of reliability for a similar purpose. Two parameters are estimated for each sample: mean difficulty and an overdispersion parameter which can be interpreted as the test's ability to detect individual differences. The proposed bivariate meta-analytical approach (random or fixed effects) pools the two parameters simultaneously and allows to perform meta-regression. The bivariate pooling yields a between-sample correlation of mean difficulty parameters and overdispersion parameters. As a side product, reliability estimates are obtained which can be employed to disattenuate correlation coefficients for insufficient reliability when no other estimates are available. A worked example illustrates the method and R code is provided. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Estimating and Using Block Information in the Thurstonian IRT Model.

Multidimensional forced-choice (MFC) tests are increasing in popularity but their construction is complex. The Thurstonian item response model (Thurstonian IRT model) is most often used to score MFC tests that contain dominance items. Currently, in a frequentist framework, information about the latent traits in the Thurstonian IRT model is computed for binary outcomes of pairwise comparisons, but this approach neglects stochastic dependencies. In this manuscript, it is shown how to estimate Fisher information on the block level. A simulation study showed that the observed and expected standard errors based on the block information were similarly accurate. When local dependencies for block sizes [Formula: see text] were neglected, the standard errors were underestimated, except with the maximum a posteriori estimator. It is shown how the multidimensional block information can be summarized for test construction. A simulation study and an empirical application showed small differences between the block information summaries depending on the outcome considered. Thus, block information can aid the construction of reliable MFC tests.

Investigating the Normativity of Trait Estimates from Multidimensional Forced-Choice Data.

The Thurstonian item response model (Thurstonian IRT model) allows deriving normative trait estimates from multidimensional forced-choice (MFC) data. In the MFC format, persons must rank-order items that measure different attributes according to how well the items describe them. This study evaluated the normativity of Thurstonian IRT trait estimates both in a simulation and empirically. The simulation investigated normativity and compared Thurstonian IRT trait estimates to those using classical partially ipsative scoring, from dichotomous true-false (TF) data and rating scale data. The results showed that, with blocks of opposite keyed items, Thurstonian IRT trait estimates were normative in contrast to classical partially ipsative estimates. Unbalanced numbers of items per trait, few opposite keyed items, traits correlated positively or assessing fewer traits did not decrease measurement precision markedly. Measurement precision was lower than that of rating scale data. The empirical study investigated whether relative MFC responses provide a better differentiation of behaviors within persons than absolute TF responses. However, criterion validity was equal and construct validity (with constructs measured by rating scales) lower in MFC. Thus, Thurstonian IRT modeling of MFC data overcomes the drawbacks of classical scoring, but gains in validity may depend on eliminating common method biases from the comparison.

Modeling Faking in the Multidimensional Forced-Choice Format: The Faking Mixture Model.

The multidimensional forced-choice (MFC) format has been proposed to reduce faking because items within blocks can be matched on desirability. However, the desirability of individual items might not transfer to the item blocks. The aim of this paper is to propose a mixture item response theory model for faking in the MFC format that allows to estimate the fakability of MFC blocks, termed the Faking Mixture model. Given current computing capabilities, within-subject data from both high- and low-stakes contexts are needed to estimate the model. A simulation showed good parameter recovery under various conditions. An empirical validation showed that matching was necessary but not sufficient to create an MFC questionnaire that can reduce faking. The Faking Mixture model can be used to reduce fakability during test construction.

Does multidimensional forced-choice prevent faking? Comparing the susceptibility of the multidimensional forced-choice format and the rating scale format to faking.

A common concern with self-reports of personality traits in selection contexts is faking. The multidimensional forced-choice (MFC) format has been proposed as an alternative to rating scales (RS) that could prevent faking. The goal of this study was to compare the susceptibility of the MFC format and the RS format to faking in a simulated high-stakes setting when using normative scoring for both formats. Participants were randomly assigned to 3 groups (total N = 1,867) and filled out the Big Five Triplets once under an honest instruction and once under a fake-good instruction. Latent mean differences between the honest and fake-good administrations indicated that the Big Five domains were faked in the expected direction. Faking effects for all traits were larger for RS compared with MFC. Faking effects were also larger for the MFC version with mixed triplets compared with the MFC version with triplets that were fully matched regarding their social desirability. The MFC format does not prevent faking completely, but it reduces faking substantially. Faking can be further reduced in the MFC format by matching the items presented in a block regarding their social desirability. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Taking the Test Taker's Perspective: Response Process and Test Motivation in Multidimensional Forced-Choice Versus Rating Scale Instruments.

The multidimensional forced-choice (MFC) format has been proposed as an alternative to the rating scale (RS) response format. However, it is unclear how changing the response format may affect the response process and test motivation of participants. In Study 1, we investigated the MFC response process using the think-aloud technique. In Study 2, we compared test motivation between the RS format and different versions of the MFC format (presenting 2, 3, 4, and 5 items simultaneously). The response process to MFC item blocks was similar to the RS response process but involved an additional step of weighing the items within a block against each other. The RS and MFC response format groups did not differ in their test motivation. Thus, from the test taker's perspective, the MFC format is somewhat more demanding to respond to, but this does not appear to decrease test motivation.

Comparing the validity of trait estimates from the multidimensional forced-choice format and the rating scale format.

The multidimensional forced-choice (MFC) format has been proposed as an alternative to rating scales (RS) that may be less susceptible to response biases. The goal of this study was to compare the validity of trait estimates from the MFC and the RS format when using normative scoring for both formats. We focused on construct validity and criterion-related validity. In addition, we investigated test-retest reliability over a period of six months. Participants were randomly assigned the MFC (N = 593) or the RS (N = 622) version of the Big Five Triplets. In addition to self-ratings on the Big Five Triplets and other personality questionnaires and criteria, we also obtained other-ratings (N = 770) for the Big Five Triplets. The Big Five in the Big Five Triplets corresponded well with the Big Five in the Big Five Inventory except for agreeableness in the MFC version. The majority of the construct validity coefficients differed between the MFC and the RS version, whereas criterion-related validities were very similar. The self- and other-rated Big Five Triplets showed higher correlations in the MFC format than in the RS format. The reliability of trait estimates on the Big Five and test-retest reliabilities were lower for MFC compared to RS. For the MFC format to be able to replace the RS format, more research on how to obtain ideal constellations of items that are matched in their desirability is needed. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

RNAi suppression of the morphine biosynthetic gene salAT and evidence of association of pathway enzymes.

Papaver somniferum L. was transformed with an RNAi construct designed to reduce transcript levels of the gene encoding the morphine biosynthetic enzyme, salutaridinol 7-O-acetyltransferase (SalAT). RNA interference of salAT led to accumulation of the intermediate compounds, salutaridine and salutaridinol, in a ratio ranging from 2:1 to 56:1. Along the morphine biosynthetic pathway, salutaridine is stereospecifically reduced by salutaridine reductase (SalR) to salutaridinol, which is subsequently acetylated by SalAT. SalAT transcript was shown by quantitative PCR to be diminished, while salR transcript levels remained unaffected. Yeast two-hybrid and co-immunoprecipitation analyses indicated an interaction between SalR and SalAT, which suggested the occurrence of an enzyme complex and provided an explanation for the unexpected accumulation of salutaridine. Decreased concentrations of thebaine and codeine in latex were also observed, while the morphine levels remained constant compared to concentrations found in untransformed control plants.

Increasing morphinan alkaloid production by over-expressing codeinone reductase in transgenic Papaver somniferum.

Only plants of the Papaver genus (poppies) are able to synthesize morphinan alkaloids, and cultivation of P. somniferum, opium poppy, remains critical for the production and supply of morphine, codeine and various semi-synthetic analgesics. Opium poppy was transformed with constitutively expressed cDNA of codeinone reductase (PsCor1.1), the penultimate step in morphine synthesis. Most transgenic lines showed significant increases in capsule alkaloid content in replicated glasshouse and field trials over 4 years. The morphinan alkaloid contents on a dry weight basis were between 15% and 30% greater than those in control high-yielding genotypes and control non-transgenic segregants. Transgenic leaves had approximately 10-fold greater levels of Cor transcript compared with non-transgenic controls. Two cycles of crossing of the best transgenic line into an elite high-morphine genotype resulted in significant increases in morphine and total alkaloids relative to the elite recurrent parent. No significant changes in alkaloid profiles or quantities were observed in leaf, roots, pollen and seed.

Metabolic engineering with a morphine biosynthetic P450 in opium poppy surpasses breeding.

Morphine biosynthesis was genetically engineered in an industrial elite line of the opium poppy (Papaver somniferum L.), to modify the production of alkaloids in plants. The cytochrome P-450-dependent monooxygenase (S)-N-methylcoclaurine 3'-hydroxylase (CYP80B3) lies on the pathway to the benzylisoquinoline alkaloid branch point intermediate (S)-reticuline. Overexpression of cyp80b3 cDNA resulted in an up to 450% increase in the amount of total alkaloid in latex. This increase occurred either without changing the ratio of the individual alkaloids, or together with an overall increase in the ratio of morphine. Correspondingly, antisense-cyp80b3 cDNA expressed in opium poppy caused a reduction of total alkaloid in latex up to 84%, suggesting that the observed phenotypes were dependent on the presence of the transgene. This study found compelling evidence, that cyp80b3 is a key regulation step in morphine biosynthesis and provides practical means to genetically engineer valuable secondary metabolites in this important medicinal plant.

Comparative qualitative and quantitative determination of alkaloids in narcotic and condiment Papaver somniferum cultivars.

In the present study morphinan, tetrahydrobenzylisoquinoline, benzo[c]phenanthridine, and phthalideisoquinoline alkaloids were determined qualitatively and quantitatively by HPLC and LC-MS analysis in tissues of the Tasmanian Papaver somniferum L. elite cultivar C048-6-14-64. The data were compared with the results from the low-morphine cultivar "Marianne". In the elite cultivar, 91.2% of the latex alkaloids consist of the three pharmaceutically most valuable alkaloids: morphine, codeine, and thebaine. In the root system, the major alkaloids are sanguinarine/10-hydroxysanguinarine and dihydrosanguinarine/10-hydroxydihydrosanguinarine. In the stems and leaves of C048-6-14-64, the same alkaloids were measured as in the latex. In the stems, a gradient in relative total alkaloid content from the top downward toward the roots was observed. The concentration of morphine was decreasing toward the roots, whereas an increasing gradient from the upper to the lower stem parts was detected for codeine. The relative total alkaloid concentration in leaves remained constant; no gradient was observed. The cultivar "Marianne" displayed a shifted pattern of alkaloid accumulation and reduced levels of total alkaloid. In the condiment cultivar, 80.5% of the alkaloids of the latex consisted of the two phthalideisoquinoline alkaloids narcotoline and noscapine. Only 18.8% of the relative total alkaloid content were morphinan alkaloids. In contrast to the narcotic cultivar, in which the benzo[c]phenanthridines in roots dominated over the morphinan and tetrahydrobenzylisoquinoline alkaloids, the concentration of benzo[c]phenanthridines in "Marianne" was similar to that of morphinan and tetrahydrobenzylisoquinoline alkaloids. These data suggest a differential alkaloid regulation in each cultivar of P. somniferum.

Transformation of opium poppy (Papaver somniferum L.) with antisense berberine bridge enzyme gene (anti-bbe) via somatic embryogenesis results in an altered ratio of alkaloids in latex but not in roots.

The berberine bridge enzyme cDNA bbe from Papaver somniferum L. was transformed in antisense orientation into seedling explants of the industrial elite line C048-6-14-64. In this way, 84 phenotypically normal To plants derived from embryogenic callus cultures were produced. The selfed progeny of these 84 plants yielded several T1 plants with an altered alkaloid profile. One of these plants T1-47, and its siblings T2-1.2 and T2-1.5 are the subject of the present work. The transformation of these plants was evaluated by PCR, and northern and Southern hybridisation. The transgenic plants contained one additional copy of the transgene. The alkaloid content in latex and roots was determined with HPLC and LC-MS. We observed an increased concentration of several pathway intermediates from all biosynthetic branches, e.g., reticuline, laudanine, laudanosine, dehydroreticuline, salutaridine and (S)-scoulerine. The transformation altered the ratio of morphinan and tetrahydrobenzylisoquinoline alkaloids in latex but not the benzophenanthridine alkaloids in roots. The altered alkaloid profile is heritable at least to the T2 generation. These results are the first example of metabolic engineering of the alkaloid pathways in opium poppy and, to our knowledge, the first time that an alkaloid biosynthetic gene has been transformed into the native species, followed by regeneration into a mature plant to enable analyses of the effect of the transgene on metabolism over several generations.