The authors analyzed the spellings of 179 U.S. children (age = 3 years, 2 months-5 years, 6 months) who were prephonological spellers, in that they wrote using letters that did not reflect the phonemes in the target items. Supporting the idea that children use their statistical learning skills to learn about the outer form of writing before they begin to spell phonologically, older prephonological spellers showed more knowledge about English letter patterns than did younger prephonological spellers. The written productions of older prephonological spellers were rated by adults as more similar to English words than were the productions of younger prephonological spellers. The older children s spellings were also more wordlike on several objective measures, including length, variability of letters within words, and digram frequency.

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Objective: Previous research has documented executive function (EF) impairments in individuals with early treated phenylketonuria (ETPKU). It remains unclear, however, whether some aspects of EF may be more affected than others. A number of factors, including small sample sizes and variability in EF tasks, have likely contributed to past mixed findings. The present objective was to elucidate further the EF profile associated with ETPKU, particularly as it relates to report-based assessment of EF. Method: Data from 286 individuals (5–48 years of age) with ETPKU on the child and adult versions of the Behavior Rating Inventory of Executive Function (BRIEF), a well-established report-based assessment tool, were analyzed. Results: The Working Memory scale showed the largest effect size in both young and older ETPKU samples, with 19% of children and 29% of adults scoring in the “abnormally elevated” range. In addition, EF impairment appeared more general (i.e., affecting more domains) in the adult sample as compared to the child sample. Exploratory analyses also suggested that the presence/absence of overall impairment on the BRIEF among our ETPKU participants could be predicted based on a small subset of items. A 10-item subset showed total classification accuracy values of 90% and above for both groups. Conclusions: Working memory represents an aspect of EF that appears to be particularly affected in individuals with ETPKU. Findings also provide preliminary support of the viability for the development and/or adoption of an abbreviated screening measure for EF difficulties in children and adults with ETPKU.

Objective: Although past studies have documented motor control impairments in individuals with early-treated phenylketonuria (ETPKU), much less is known regarding motor learning in ETPKU. The goal of the present study was to advance our understanding on this front. Method: We isolated and examined motor kinematics associated with the learning of a rapid aimed limb movement in a sample of 40 individuals (13-34 years of age) with ETPKU and a matched comparison group of 40 individuals without phenylketonuria (PKU). Indices of motor learning included overall movement duration as well as the relative proportion of movement time devoted to ballistic and corrective submovements. (Note that practice of motor movements in nonclinical populations is associated with, not only improvements in overall speed, but also reduction in the proportion of movement time devoted to corrective submovements relative to an initial ballistic submovement.) Results: A group-by-time interaction was found. With practice, the non-PKU group showed a significant reduction in the proportion of movement time devoted to the corrected (as compared to the ballistic) submovement. A similar change was not observed for the ETPKU group. In addition, within the ETPKU group, the rate of improvement in total movement duration was correlated with recent blood phenylalanine levels (an indicator of treatment adherence). Conclusions: Motor learning is adversely affected in individuals with ETPKU. Further investigation into the behavioral and neural mechanisms of motor learning in ETPKU will advance our understanding of the etiologic basis for this disruption as well as how it relates to the broader neurocognitive profile of ETPKU.

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Bayesian methods are becoming increasingly used in applied psychological research. Previous researchers have thoroughly written about much of the details already, including the philosophy underlying Bayesian methods, computational issues associated with Bayesian model estimation, Bayesian model development and summary, and the role of Bayesian methods in the so‐called replication crisis. In this paper, we seek to provide case studies comparing the use of frequentist methods to the use of Bayesian methods in applied psychological research. These case studies are intended to ‘illustrate by example’ the ways that Bayesian modelling differs from frequentist modelling and the differing conclusions that one may arrive at using the two methods. The intended audience is applied psychological researchers who have been trained in the traditional frequentist framework, who are familiar with mixed‐effects models and who are curious about how statistical results might look in a Bayesian context. Along with our case studies, we provide general opinions and guidance on the use of Bayesian methods in applied psychological research.

Objective: Relative to youth with early-treated phenylketonuria (ETPKU), much less is known regarding the cognitive profile of adults with ETPKU. The present study aimed to address this gap by providing a comprehensive assessment of neuropsychological functioning among adults with ETPKU. Method: A sample of 40 adults with ETPKU (ages 18 – 36) and a demographically matched group of 32 healthy individuals without PKU participated. Participants completed a comprehensive neuropsychological battery including the NIH Toolbox, Wechsler Abbreviated Scale of Intelligence – Second Edition (WASI-II), Conners’ Continuous Performance Test (CPT-3), select subtests from the Weschler Adult Intelligence Scale – Fourth Edition (WAIS-IV) as well as several self-report measures of cognitive and psychoemotional functioning. Scores from these tests were combined to create cognitive composites reflecting overall task performance in the areas of verbal ability, visuospatial skills, executive functioning, motor skills, and processing speed. Results: No group differences were observed for full scale IQ or verbal ability. However, individuals with ETPKU demonstrated poorer performance on measures of executive functioning, processing speed, motor skills, and visuospatial skills as compared to the non-PKU group. Within the ETPKU group, recent blood phenylalanine levels (an indicator of metabolic control) were significantly correlated with performance across most cognitive domains and aspects of psychological functioning. Conclusions: Present findings suggest that the neuropsychological profile of adult ETPKU is characterized by circumscribed impairments in select cognitive domains. In addition, the results underscore the importance of maintaining metabolic control across the lifespan in individuals with ETPKU.

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