Studies of the course of the condition by Kanner and Eisenberg, Kanner and Lesser (1958), Rutter (1968), Rutter and Lockyer (1967) show that in the case of the Kanner syndrome or of Rutter's infantile psychosis, which is probably fairly identical with the Kanner syndrome, over 50% of the cases so far followed up finally require treatment in long-stay institutions. Of the 63 cases (Kanner and Eisenberg), 31 remained unable to speak, while 32 had developed a communicative language by the age of 5. Sixteen of this group were regarded as well adapted socially, while only one individual in the non-speaking group had managed this. Rutter and Greenfeld (1966) found that in 29 out of 63 cases useful speech was lacking. While Eisenberg discovered only one child that developed useful speech after the age of 5, Rutter (1965), Rutter and Greenfeld (1966), Rutter quoted in Wing et al. (1966) describe how out of 31 children who were non-verbal at the age of 5 no less than 7 gradually developed speech by the age of 11. While Kanner and Eisenberg, in accordance with their observations, ascribe a very definite (negative) prognostic significance to the lack of speech at the age of 5, Rutter rates the results of intelligence tests higher. In studies performed with various co-workers (Greenfeld, 1967, or Lockyer, 1967), he found that the degree of intelligence provided a better means of prediction than the presence or non-presence of speech. Non-verbal children who had a relatively good I.Q. or S.Q. (at least over 60) before their 5th birthdays also showed a relatively favourable development later on.