This document below addresses a lot of the points raised here, it's taken from the Selective Mutism Resource Manual, the 'gold standard' treatment manual for Selective Mutism. The section on 'low profile selective mutism' is particularly worth a read.
An information sheet for parents and professionals
QUIET CHILD or SELECTIVE MUTISM?
Some children are naturally quiet and present a similar personality at home and in school. They do not venture a lot of information but can become quite animated with a familiar topic that captures their imagination. Provided they are coping academically, have a good friend or two and are not being bullied, quiet children move easily between their home and school environments without anxiety. Their relaxed body language and facial expressions show that they are happy to listen, without necessarily feeling the need to talk as much as their noisier peers.
Not all quiet children are comfortable with silence
For some quiet children and young people, however, it’s a very different picture. They may have an anxiety disorder called selective mutism (SM) – a phobia of speaking in specific situations. These individuals do not want to be quiet. They may have plenty to say but are unable to speak freely – just the thought of speaking to certain people fills them with dread and can trigger a panic or ‘freeze’ reaction. Typically, they feel a blockage in the throat as their muscles tense, and they cannot produce sound to talk, laugh or cry out loud.
When is it selective mutism?
Although no two children with SM are exactly the same, they all have:
• the ability to talk freely to certain people and not others (often described as ‘two personalities’)
• a consistent pattern of situations where speech is possible and not possible
• avoidance or reluctance to attend events where they will be expected to speak
• high levels of distress when their difficulty speaking freely is not understood.
Some children with SM are recognised more easily than others …
High-profile selective mutism
These children and young people do not speak at all to certain people. They are therefore quite easily recognised by the observable contrasts in their speaking patterns. They may speak to children in their educational setting, for example, but not adults. They may speak freely to their friends in the playground but not in the classroom where they will be overheard by other people. They may speak to relatives they see on a regular basis, but not those they see infrequently. And, typically, they speak to parents as soon as they move out of earshot of other people.
Once recognised, there is generally a willingness to accept that these children have an anxiety-related communication difficulty. Steps can be taken to remove all pressure to speak, followed by a gradual step-by-step approach to face their fear of talking. Importantly, with the right support, the children themselves recognise that SM is not part of their personality, but something that can be overcome, like other fears they worked through when they were younger; for example, a fear of darkness, fireworks or jumping in at the deep end of the swimming pool.
Low-profile selective mutism
Children with low-profile SM speak when prompted, so adults usually regard them as either shy or quiet and don’t realise that speaking provokes the same intense anxiety as high-profile SM. These children manage to say a few words because of their strong desire to be compliant. In effect, their fear of the consequences of not speaking outweighs their fear of speaking, but this fine balance only operates when they are fairly confident about the subject matter. So, in school, they may answer the register or read aloud on request, and can answer simple questions, albeit with a much quieter voice and less eye contact than they would use at other times. They may occasionally initiate an essential request, such as using the toilet, or pass on a short message when instructed. In contrast, they do not enter into reciprocal two-way conversation or initiate conversations, except with close friends and family.
Until it is recognised that they are unable to report bullying or illness, seek help, ask permission or explain themselves, these young people are at risk. Their difficulties may go unnoticed and they may be reprimanded, rather than supported, when they don’t speak up for themselves. Repeated encouragement to speak louder and make more of a contribution only heightens their discomfort. If their difficulties continue to be mismanaged, they are likely to speak less and less with an increase in school absence and decrease in self-esteem.
Children with low-profile and high-profile SM need the same help to achieve anxiety-free communication and participation.
Supporting children and young people who have selective mutism
• Appoint a member of staff to make a special relationship with the child or young person on a one-to-one basis.
• Actively support the development of friendships and inclusion in pastoral activities.
• Be patient and don’t pressurise the child or young person to speak; focus on discovering and acknowledging their many strengths and attributes.
• Seek advice or information on providing appropriate help from:
NHS choices www.nhs.uk/conditions/selective-mutism
Selective Mutism Information and Research Association (SMIRA)
www.smira.org.uk
Source: The Selective Mutism Resource Manual by Maggie Johnson and Alison Wintgens, Speechmark Publications