Intellectual disability (ID) is often accompanied by delays in emotional development (ED) that may result in challenging behavior. Insight into emotional functioning is crucial for appropriate diagnostic assessment in adults with ID. However, few standardized assessment instruments are available. The aim of this study was to develop a short, psychometrically sound instrument for assessing levels of ED in individuals with ID: The Scale of Emotional Development - Short (SED-S), which can be applied to adults. The Scale for ED - Revised2 (SED-R2) was taken as a point of departure. In a first step, the validity and observability of the items (N=556) in the SED-R2 were assessed by 30 experts from Germany, Belgium, and The Netherlands. The SED-S was then constituted in a consecutive consensus process, in which items to be included were selected based on their assessments and subsequently rephrased, and in which the structure and method of administering the new scale were agreed upon. The SED-S consists of 200 binary items describing five levels of emotional functioning (reference ages: 0-12 years) within eight domains: Relating to His/Her Own Body, Relating to Significant Others, Dealing with Change - Object Permanence, Differentiating Emotions, Relating to Peers, Engaging with the Material World, Communicating with Others, and Regulating Affect. The SED-S offers an empirical-based, practical tool to assessing ED in adults with ID. Further research will be needed to meet the requirements of a standardized diagnostic instrument.

Intellectual disability is a neurodevelopmental disorder with a related co-occurrence of mental health issues and challenging behaviors. In addition to purely cognitive functions, socio-emotional competencies may also be affected. In this paper, the lens of developmental social neuroscience is used to better understand the origins of mental disorders and challenging behaviors in people with an intellectual disability. The current concept of intelligence is broadened by socio-emotional brain functions. The emergence of these socio-emotional brain functions is linked to the formation of the respective neuronal networks located within the different parts of the limbic system. Thus, high order networks build on circuits that process more basic information. The socio-emotional skills can be assessed and complement the results of a standardized IQ-test. Disturbances of the brain cytoarchitecture and function that occur at a certain developmental period may increase the susceptibility to certain mental disorders. Insights into the current mental and socio-emotional functioning of a person may support clinicians in the calibration of treatment and support. Acknowledging the trajectories of the socio-emotional brain development may result in a more comprehensive understanding of behaviors and mental health in people with developmental delays and thus underpin supports for promotion of good mental health in this highly vulnerable population.