But as Dr Nguyen Cam pointed out, the absence of expression was one of those cultural differences it was important to explain.
When doctors were trying to assess mental illness, there was always the risk that they would interpret the quiet stare characteristic of his countrymen as abnormal. It is not.
Such linguistic and medical interpretation is at the core of the Vietnamese Mental Health Project run by Dr Cam.
From his base in Brixton, south London, he and his seven staff help prevent psychiatric misdiagnoses through cultural misunderstanding and provide back-up for 200 mentally ill men and women among the capital's 17,000-strong Vietnamese community.
Developing from a research programme into mental problems among refugees who fled to Britain to escape atrocities in their homeland, the project acts as a link between the medical and social authorities and those they are trying to help.
The problems are not just linguistic. Many have found it difficult to adapt to life in Britain. Furthermore, the traditional Vietnamese attitude to mental health has required special efforts to break down.
Memories of executions, the destruction of their homes and villages, prison and torture have left a catalogue of trauma and psychotic disorders requiring treatment.
Dr Cam said: "We value Western medicine, but Vietnamese think [it] should work in 10 to 15 days. If they have to continue treatment they think that's wrong so they stop and it leads to lapses."
With the implementation of the care in the community programme for the mentally ill, the need for support has become even greater. Dr Cam, 61, is delighted at the grant. The project lost a worker last month and had no funds for him and his administration and finance officer, Ms Cuc Le, from next April.
The National Lottery Charities Board decision to bestow pounds 174,000 has transformed its future. "I'm glad because I think we deserve it," he said.
Just down the road there was evidence to support him. As well as running two drop-in centres, the project has a permanent home for six mentally ill people. Felix Liu teaches the residents self-reliance, how to deal with every-day life and even how to cook - a vital skill for men who traditionally do not.
Duong Lai, 46, first became ill when he was slung in jail for a year before being expelled from north Vietnam. Another resident spent 10 years in an overcrowded Hong Kong detention centre before escaping.
Thanks to the project's support, former resident Hong Son Ly, 39, is now living in his own home. He had popped into the centre yesterday to see his friends. Son Thach, 38, was a boat mechanic in Vietnam before joining the "boat people" exodus in 1980. "I like it here," he said.Reuse content