Two ways into the hall of mirrors: Language exposure and lossy memory drive cross-linguistic grammaticality illusions in language models

AbstractReaders of English — but not Dutch or German — consistently show a grammaticality illusion: they find ungrammatical double-center-embedded sentences easier to process than corresponding grammatical sentences. If pre-trained language model (LM) surprisal mimics these cross-linguistic patterns, this implies that language statistics explain the effect; if, however, the illusion requires memory constraints such as lossy context surprisal (LCS), this suggests a critical role for memory. We evaluate LMs in Dutch, German, and English. We find that both factors influence LMs’ susceptibility to grammaticality illusions, and neither fully account for human-like processing patterns.