[Invariability of stimulus recognition by dolphins]

The echo-location characteristics were studied in dolphins with the aid of transformation of stimuli not altering the reception characteristics in analysing systems. The dolphin locator was shown to be able to single out a class of equivalent in respect to certain transformations echo-signals. The probability of the target recognition is invariable in respect to transformations of homothetic type and module transformations, i.e. the principle of invariability spreads over the work of dolphin's auditory analyser in active regimen too.