Pluralistic ignorance
In social psychology, pluralistic ignorance is a situation in which a majority of group members privately reject a norm, but go along with it because they incorrectly assume that most others accept it. This is also described as "no one believes, but everyone thinks that everyone believes". In short, pluralistic ignorance is a bias about a social group, held by the members of that social group.
Selective mutism
The former name "elective mutism" indicates a widespread misconception among psychologists that selective mute people choose to be silent in certain situations, while the truth is that they often wish to speak but have difficulty doing so. To reflect the involuntary nature of this disorder, the name was changed to "selective mutism" in 1994.
The incidence of selective mutism is not certain. Due to the poor understanding of this condition by the general public, many cases are likely undiagnosed. Based on the number of reported cases, the figure is commonly estimated to be 1 in 1000, 0.1%. However, a 2002 study in "The Journal of the American Academy of Child and Adolescent Psychiatry" estimated the incidence to be 0.71%.