KBG syndrome is a neurodevelopmental disorder (NDD) caused by loss-of-function of the ANKRD11 gene. The core phenotype comprises developmental delay (DD)/ intellectual disability (ID) and several specific facial dysmorphisms. In addition, both ADHD- and ASD-related symptoms have been mentioned. For the correct understanding of these developmental and behavioral characteristics however, it is of great importance to apply objective measures, which seldom has been done in patients with KBG syndrome. In this study, intelligence profiles of patients with KBG syndrome (n = 18) were compared with a control group comprising patients with NDD caused by various other genetic defects (n = 17), by means of the Wechsler scales. These scales were also used to measure speed of information processing, working memory, verbal comprehension and perceptual reasoning. No significant differences were found in the global level of intelligence of patients with KBG syndrome as compared to the patient genetic control group. The same was true for Wechsler subtest results. Hence, behavioral problems associated with KBG syndrome cannot directly be related to or explained by a specific intelligence profile. Instead, specific assessment of neurocognitive functions should be performed to clarify the putative behavioral problems as observed in this syndrome.

The concept of executive functions plays a prominent role in contemporary experimental and clinical studies on cognition. One paradigm used in this framework is the random number generation (RNG) task, the execution of which demands aspects of executive functioning, specifically inhibition and working memory. Data from the RNG task are best seen as a series of successive events. However, traditional RNG measures that are used to quantify executive functioning are mostly summary statistics referring to deviations from mathematical randomness. In the current study, we explore the utility of recurrence quantification analysis (RQA), a non-linear method that keeps the entire sequence intact, as a better way to describe executive functioning compared to traditional measures. To this aim, 242 first- and second-year students completed a non-paced RNG task. Principal component analysis of their data showed that traditional and RQA measures convey more or less the same information. However, RQA measures do so more parsimoniously and have a better interpretation.

Cognitive difficulties are argued to be common in patients with Noonan syndrome spectrum disorders (NSSDs), but findings are based on studies in which patients with variants in PTPN11 (prevalence ~50%) were overrepresented. The current study, using a structured clinical approach, describes the cognitive phenotype and psychopathology of 100 patients (aged 6 to 61 years) with nine different gene variants in the Ras/MAPK pathway underlying NSSDs (PTPN11n = 61, PTPN11 Noonan syndrome with multiple lentigines n = 3, SOS1n = 14, KRASn = 7, LZTR1n = 5, RAF1n = 4, SHOC2n = 2, CBLn = 2, SOS2n = 2). After weighted assessment and bootstrapping of the results of individual neuropsychological assessments and measures of psychopathology, cognitive performances in most variant groups were within the ranges of expectation. IQs were significantly lower in patients with variants in PTPN11, KRAS, RAF1, and SHOC2, but no specific cognitive impairments were found. The performances of younger participants (<16 years of age) did not differ from those of adults. Alexithymia and internalizing problems were more frequent in patients with variants in PTPN11 and SOS1, while PTPN11 patients also showed higher levels of externalizing problems. These results stress the need to take intelligence into account when interpreting lower cognitive performances in individual neuropsychological assessments, which is crucial for an adequate understanding and guidance of patients with NSSDs.

The neuropsychological construct of executive functions (EFs), and the psychometric Cattell–Horn–Carroll (CHC) theory of cognitive abilities are both approaches that attempt to describe cognitive functioning. The coherence between EF and CHC abilities has been mainly studied using factor-analytical techniques. Through multivariate regression analysis, the current study now assesses the integration of these latent constructs in clinical assessment. The predictive power of six widely used executive tasks on five CHC measures (crystallized and fluid intelligence, visual processing, short-term memory, and processing speed) is examined. Results indicate that executive tasks—except for the Stroop and the Tower of London—predict overall performance on the intelligence tests. Differentiation in predicting performance between the CHC abilities is limited, due to a high shared variance between these abilities. It is concluded that executive processes such as planning and inhibition have a unique variance that is not well-represented in intelligence tests. Implications for the use of EF tests and operationalization of CHC measures in clinical practice are discussed.