  It is shown that different ways of interacting strings formed in high energy
nucleus-nucleus collisions cause a different strength of the chaoticity
parameter lambda of Bose-Einstein correlations. In particular, in the case of
percolation of strings, lambda shows a peculiar dependence on the string
density, very similar to the dependence of the fractional average cluster size.
In both, the derivative on the string density is maximum at the critical point.
The reasonable agreement with the existing experimental data indicates that
percolation of strings can actually occurs.
