The goal of the study is to analyze the morphological processing of real and novel verb forms by heritage speakers of Russian in order to determine whether it differs from that of native (L1) speakers and second language (L2) learners; if so, how it is different; and which factors may guide the acquisition process. The experiment involved three groups of subjects: 28 adult native speakers, 14 adult heritage speakers, and 17 beginning American learners of Russian. The results demonstrate that (1) novel form production in heritage processing, as in native and L2 processing, is rule-based, and that rule application--i.e. the generalization rate of conjugational patterns--depends on the input-based mechanism of statistical probabilities (to be defined below), and (2) that heritage speakers' mental representations of morphological structures are unstable and their morphological processing is different from either adult native or L2 processing. (Contains 4 tables, 5 figures and 7 notes.)