Research shows that most children with selective mutism were anxious in social situations from an early age. Contrary to many popular ideas, most selectively mute children have not experienced trauma. Rather their history often includes a toddler period of appropriate language development at home, but clingy, dependent behavior in the presence of unfamiliar or infrequently encountered people. Some children have shown mild forms of separation anxiety, although overt refusal to attend school is not usual. For children for whom English is a second language, case studies usually indicate that the children were not comfortable speaking with people in their first language either.

At this time, researchers believe that most selective mutism is a form of social phobia: that is, an anxiety disorder that reflects inhibited social actions for fear of embarrassment or concerns that others will judge them negatively. Some children have reported that their throats clog up when looking at others as if their vocal chords will not permit them to speak. It is probable that children with the condition have inhibited dispositions as part of their personality characteristics. Anxiety disorders often develop in such inhibited children because they have not learned to quiet their reactions or they have not learned to cope with their fears. It is believed that children who demonstrate selective mutism are a subset of inhibited children who have not learned to quiet their nervous reactions in social situations. Well-intentioned family members who are aware of a child's anxiety probably supported their limited use of speech by talking for them. Initially, this is not a problem, but, as the condition persists, support has probably become overly protective. By the time the condition is diagnosed, children have learned to communicate nonverbally for several years so that their patterns are usually well developed. Often, when the children are pushed, even mildly to speak for themselves, they may have overt outbursts and oppositional behavior. In summary, most professionals believe that selective mutism results from a negative interaction of a child's disposition with family reactions that inadvertently support withdrawal and lack of communication.