Autism Spectrum Disorder (ASD) is clinically characterized by abnormalities in complex behaviors, which are currently classified under two main criteria: persistent deficits in social communication and interaction, and restricted, repetitive patterns of behavior, interests, or activities (DSM-5). Extensive research has identified impairments in higher-order abilities across all neuropsychological domains associated with ASD including in individuals with higher intellectual abilities. These impairments encompass deficits in emotion perception and regulation), perspective-taking, pragmatic language, language comprehension, concept formation, cognitive flexibility, face perception, as well as self-regulation and motor. These impairments have been widely replicated. The documentation of deficits in complex cognitive and motor functions has led researchers to explore potential common cognitive mechanisms that may underlie one or more of these challenges. One potential mechanism that could explain the diverse profile of neuropsychological deficits observed in autism spectrum disorder (ASD) is a fundamental impairment in the speed at which affected individuals process information. ASD is frequently confounded with intellectual disability (ID), leading to some ambiguity regarding the extent to which ID contributes to processing speed deficits. This overlap makes it challenging to isolate the specific role that ASD-related cognitive impairments play in slowing information processing, as the effects of intellectual disability may compound or influence these deficits [1].

The processing speed of children with neurodevelopmental disorders, including Autism Spectrum Disorder (ASD) and Intellectual Disability (ID), has been a central topic of research in both clinical and educational settings. Processing speed is a key cognitive function that impacts various areas of daily life, such as academic achievement, problem-solving skills, and social interactions. Although there is substantial research on cognitive differences in children with ASD and ID, more direct comparisons are needed to gain a deeper understanding of the unique challenges faced by these groups. In particular, processing speed delays in children with autism have been associated with difficulties in tasks that require rapid responses, such as timed cognitive assessments [2,3]. Similarly, Individuals with intellectual disability often experience deficits in processing speed, which can impact various aspects of cognitive functioning and mental processes. The rate at which information is processed is a crucial element of cognitive abilities and plays a significant role in the performance of many mental tasks. Slower information processing speed can lead to functional impairments that disrupt overall brain function [4]. Children with Autism Spectrum Disorder (ASD) often face considerable challenges in processing speed, especially in tasks that demand quick motor responses, the ability to shift attention, and the integration of sensory information. Studies have shown that these children frequently exhibit delayed processing times in both verbal and non-verbal tasks [5]. Moreover, the processing difficulties observed in children with ASD may be linked to broader challenges in executive functioning, which includes tasks like planning, attention control, and cognitive flexibility. For example, children with ASD may take longer to complete tasks that involve multiple steps or need additional time to process and respond to social interactions [6].

On the other hand, Intellectual impairment or disability is a condition marked by reduced cognitive abilities, leading to challenges in performing daily activities and acquiring new information. Individuals with intellectual disability often need more time and support to learn, and education plays a critical role in diagnosing this condition and identifying cognitive challenges in children [7, Mafuba, 2023]. According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision [DSM-5-TR, 15], the global prevalence of intellectual disability is estimated to be around 10 per 1,000 people. Children with Intellectual Disability (ID) often experience generalized delays in processing speed that affect a wide range of cognitive domains. Intellectual disability is defined by limitations in both intellectual functioning (IQ below 70) and adaptive behavior, which can impact daily life skills such as communication, self-care, and socialization. Unlike Autism Spectrum Disorder (ASD), which mainly affects social cognition and executive functioning, ID is characterized by more global cognitive delays that influence multiple aspects of processing, including memory, attention, and problem-solving abilities [8]. Research indicates that children with ID, especially those with moderate to severe impairments, tend to process information more slowly across both verbal and non-verbal tasks. For instance, tasks requiring verbal fluency, visual-spatial processing, and even simple arithmetic often take longer for children with ID to complete, even when compared to peers of similar age and IQ levels (Boat, 2015). This slower processing speed in children with ID is commonly linked to broader cognitive limitations, including reduced working memory capacity and slower processing of both sensory and conceptual information. Researchers agree that while information processing speed may not be the primary factor in diagnosing intellectual disability, it is a crucial executive function that tends to develop with age. The speed at which individuals with intellectual disability process information can profoundly affect their performance on neuropsychological tasks and other executive functions [16]. Studies have suggested that deficits in information processing speed can have a significant impact on children's language, verbal, and mathematical skills, leading to challenges in reading, learning, and understanding words (Terrell, 2014).

Comparing processing speed in children with autism spectrum disorder (ASD) and intellectual disability (ID) is essential for understanding the unique needs of each group and for developing effective intervention strategies. Although both populations experience challenges with processing speed, the underlying causes of these difficulties often differ. In ASD, processing speed deficits are frequently associated with sensory processing issues and difficulties in social cognition, while in ID, impairments in processing speed are more likely to result from global cognitive delays (Pennington et al., 2003). These differences suggest that interventions should be specifically tailored to the cognitive profiles of each group. For children with ASD, interventions may focus on enhancing sensory processing and executive function, with an emphasis on helping them process both social and non-social information more efficiently. In contrast, interventions for children with ID might concentrate on fostering general cognitive development, improving working memory, and enhancing attention to help boost processing speed across a range of tasks (Fowler et al., 2012).

While research into the processing speed deficits in children with Autism Spectrum Disorder (ASD) and Intellectual Disability (ID) has made significant strides, several gaps remain in understanding the underlying mechanisms and effective interventions. One key limitation is the variability of findings across studies. Some studies suggest that children with ASD or ID have significantly slower processing speeds compared to typically developing peers, while others report more nuanced or inconsistent results. These inconsistencies may be due to differences in sample size, age groups, cognitive assessment methods, and the severity of the disabilities, pointing to the need for more standardized and robust research methodologies.

Furthermore, most existing studies focus on specific domains of cognitive processing, such as attention or memory, rather than investigating processing speed in a comprehensive manner. This lack of a holistic approach limits our understanding of how processing speed deficits interact with other cognitive difficulties, such as executive function or social cognition, which are particularly prominent in children with ASD. Additionally, many studies have primarily concentrated on children with ADHD or other neurodevelopmental disorders, making it challenging to generalize findings to the ASD and ID populations.

This article aims to explore and compare the processing speed of children with ASD and ID, drawing on recent studies to highlight similarities and differences between these groups. Understanding the nuances of processing speed in these populations is essential for developing more effective diagnostic criteria and intervention strategies. By examining both shared and distinct cognitive challenges, researchers and clinicians can tailor their approaches to better address the specific needs of children with ASD and ID, ultimately improving their educational and developmental outcomes.