This eye-tracking study investigated how German native-speaking adults process formality-register congruence and morphosyntactic congruence during sentence reading. Morphosyntactic processing has been robustly observed, but less attention has been given to potentially more variable knowledge effects, involving processes like reconciling (in)congruence between context formality and register of a target sentence.

40 participants read German context sentences conveying a formal or informal situation, and a target sentence containing a high- or low-register verb – e.g., Engl. transl.: “The policeman detained (high-register) / grabbed (low-register) the activist” –which matched or mismatched the formality of the context. We crossed this manipulation with that of subject-verb agreement (match/mismatch) – e.g., Engl. transl.: “The policeman *detain (high-register) / *grab (low-register) the activist”.

Inspired by research on context incongruence effects, we predicted longer reading times at the verb and post-verb region for formality-register mismatches (vs. matches). At these regions, however, we only replicated effects of morphosyntactic violations; context formality-register congruence effects were more subtle and occurred later (in total time at the post-verb region). Our eye-tracking findings suggest that, at least in the presence of outright morphosyntactic violations, formality-register congruence effects require more time to unfold during sentence reading.