In his speech Professor Johnstone criticised the "marginal and very costly" approach to the teaching of modern languages in Scottish primary schools. He said it was "hypocritical" for a major national programme to rely on just one or two trained teachers in each school.
He made clear that he was not criticising the modern languages training for primaries or the quality of the teachers - 3,750 of whom will have been through the crash programme by October at a cost of pound;16 million. In Scotland four out of five primary six and seven pupils are now exposed to a foreign language.
But Professor Johnstone forecast that increasing contacts with other schools in different cultures, aided by the new technologies, would eventually stimulate language learning and require all primary teachers to have training in two or more languages.
His research into pupils' attitudes during the primary modern languages pilot in Scotland showed that eight year olds "dived in" and were much less anxious than 11 year olds. Professor Johnstone said although "you're never too old to start", the main conclusion from the evaluation had to be "it's better to catch them young".
A survey carried out for the EU last year confirmed that Scotland and the rest of the UK begin language teaching much later than in other European countries. Some countries start at age six, compared to 10 in Scotland and 11 in England and Wales. But an early start for languages is rarely compulsory in Europe.
Professor Johnstone acknowledged that the pay-off in later years from heavy investment in primary modern languages was "not strong and not clear". A forthcoming EU report reviews available research and points out that such advantages as have been found tend to be limited to listening skills and to faster learners.
A larger number of studies do reveal positive attitudes to modern languages by the time pupils reach the end of primary school. But maintaining that momentum into secondary appears to be a stubborn problem across Europe.
Nevertheless, Professor Johnstone said evidence from Croatia suggested that an early start was an advantage. Croatian schools begin foreign language teaching at six, with good quality teaching at regular intervals - one hour a day for the first two years. Another factor in the Croatian success, Professor Johnstone believes, is the close and conscious link between mother tongue teaching and the foreign language.