What Really Counts: Theoretical and Empirical Aspects of Counting Behaviour in Simple RNNs
Nadine El Naggar from City, University of London presented research on RNN learning of counting behavior, formalizing it as Dyck-1 acceptance. Empirically, RNN models struggle to learn exact counting and fail on longer sequences, even when weights are correctly initialized. Theoretically, Counter Indicator Conditions (CICs) were proposed and proven necessary/sufficient for exact counting in single-cell RNNs, but experiments show these CICs are not found or are unlearned during training. Why it matters: This work highlights challenges in RNNs learning systematic tasks, suggesting gradient descent-based optimization may not achieve exact counting behavior with standard setups.