Autism spectrum disorder
People with ASD exhibit specific types of perception and cognition, that is, they tend to show a bias for local rather than global cognition. Weak central coherence (Frith & Happé, 1994) is an interesting theory by which to explain these characteristics of ASD. Kasai and Murohashi (2013) investigated the tendency of attentional bias toward local details, which is considered to be one of the traits of perception in autism. They examined ERPs in a sustained focal-attention task that involved bilateral stimulus arrays. Their results suggested that bottom-up processing in perceptual organization varies with the autism spectrum quotient (AQ).
People with ASD have some difficulties with face recognition. Such difficulties have been implicated in the difficulties that people with ASD have with social interaction. Kikuchi, Senju, Hasegawa, Tojo, and Osanai (2013) investigated the processing of facial expressions in children with ASD. They examined responses to low spatial frequency images with blurred facial features and high spatial frequency images with rich facial features. Their results suggest that children with ASD are biased toward processing facial expression based on local information.
Children with ASD often have better relationships with objects than with other humans. They have difficulties in communicating with people. Kozima (2013) proposes an interesting theory to explain this tendency. “Cognitive granularity” refers to the size of the basic elements that can operate in one's cognitive system. According to this theory, people with ASD have finer cognitive granularity, and as a result they have difficulties with predicting and controlling their social world, but not the physical world.
Children with ASD interact better with robots than with other humans. Takahashi, Saito, Okada, and Omori (2013) investigated the mechanism of online mentalizing with an index of entropy in human-robot competitive games. Mentalizing is the ability to attribute a mental state to another agent, and is particularly required in actual social contexts. They claim that people with ASD have difficulties with online mentalizing. They propose that there are two separate mentalizing processes: an explicit, logical reasoning process and an implicit, intuitive process. The latter is a core process for online mentalizing, and this is why people with ASD have difficulties in communicating with others.
People with ASD often have specific sensory abnormalities (such as hypersensibility or hypoesthesia), but the mechanism is not yet clear. Toyomaki and Murohashi (2013) investigated the relation between such sensory abnormalities and social cognition. A salience network dysfunction hypothesis has recently been proposed (Menon & Uddin, 2010; Uddin & Menon, 2009). This neuroscientific theory states that the network that integrates external sensory stimuli with internal states mediates interactions between the large-scale networks involved in externally and internally oriented cognitive processing. According to this theory, the salience network in people with ASD shows chronically low activity, and as a result they have difficulties with social cognition and self-referential processing.
While people with ASD have difficulties with communication, people with Williams syndrome (WS) exhibit hypersociability (Bellugi, Adolphs, Cassady, & Chiles, 1999; Capitao, Sampaio, Fernandez, Sousa, Pinheiro, & Gibcalves, 2011). These conditions have opposite characteristic traits of communication (Asada & Itakura, 2012). Inui (2013) investigated cortical network abnormalities in ASD and WS, and discussed the abnormalities he observed in five structures (amygdala, hippocampus, orbitofrontal cortex, inferior frontal cortex, posterior parietal lobe) in ASD and WS. He proposes an interesting neuroscientific framework to understand these findings in a unified manner.
People with DD have difficulties with reading and often writing. Snowling and Hulme (2013) reviewed reading impairment in children. They discuss definitions, the continuous variation in reading skills, the overlap between reading and language disorders, and evidence-based interventions for reading disorders. They also address the differences between alphabetic and nonalphabetic systems. They think that children who are at risk of dyslexia can be identified early, before they develop a sense of failure, and discuss the need for timely intervention based on assessments. They insist that this disorder is dimensional rather than a discrete diagnostic.
Attention deficit and hyperactivity disorder
People with ADHD often have difficulties controlling their responses. They often have inefficient executive functions (e.g., set shifting, response inhibition, planning, working memory). Robinson and Tripp (2013) investigated neuropsychological functioning (intellectual function, design fluency, spatial organization, and visual memory) in children with ADHD and a control group. They divided children with ADHD into those with persistent ADHD and those with ADHD in partial remission, and found that persistent ADHD was associated with greater cognitive impairment.
I hope that this special issue can stimulate both studies on developmental disorders and studies in cognitive science. Studies on developmental disorders are needed to promote understanding of the mechanisms for perception, memory, learning, emotion, and other basic psychological functions. I believe that if researchers in basic science and clinical researchers draw from each other's studies from a dimensional viewpoint, we may be able to achieve a deeper understanding of human nature.