Observation and clinical accounts of the behavior of children with SM are varied. It is important to realize that the majority of children and adolescents are as normal and appropriate as their peers when in a comfortable environment. Parents will often comment about how boisterous, sociable, humorous, inquisitive, talkative and even bossy and assertive these children are at home. However, what differentiates children with SM is their severe behavioral inhibition and inability to speak in certain social settings. When in these settings, children with SM feel as if though they are continuously “on stage” and experience many of the same symptoms that people have with stage fright. Some children with SM also report somatic complaints such as nausea, headaches, and stomachaches or may experience vomiting, diarrhea and an array of other physical symptoms before school or outings.

When in school or in other anxiety provoking settings, some children become much more withdrawn that others and may stand motionless and expressionless and may demonstrate awkward or stiff posture and body language. They may experience a great deal of emotions including anxiety, sadness and frustration but may not express these emotions visibly and some children have even been too inhibited to express feeling pain when injured on the playground. Many children with SM will turn away or hang their head to avoid eye contact, chew or twirl their hair or withdraw into a corner. Over time, some children learn to cope and participate in certain social settings by performing nonverbally or by talking quietly to a select few. There are also variations in the degree of outward anxiety or nervousness. Some children display facial expressions and body language that are obviously due to fear or nervousness. Others may appear outwardly calm and may be able to communicate nonverbally. It is the latter type of child that is most often misinterpreted as being defiant or oppositional since they do not show visible signs of being nervous.

Children with SM tend to have difficulty initiating and may be slow to respond even when it comes to nonverbal communication (e.g., pointing, nodding, shaking head no). This can be quite frustrating to the child and may lead to falsely low test scores and misinterpretation of the child’s cognitive abilities. It is for these reasons that assessment should be conducted by someone familiar with anxiety and how it may manifest in performance situations such as taking a test.

Social relationships can be very difficult for children with SM although some are well liked by peers. In many cases, classmates tend to take on a protective role and/or try to speak for the child with SM. Even for those fortunate enough to have supportive peers, there is no doubt that SM stifles social growth and development and limits social interaction. In worse case scenarios, some children are socially isolated, are victims of teasing and bullying and are completely unable to defend themselves. This seems to be more of a problem for older children and bullying may be more common for boys with SM than for girls.