“All that glitters is not … alone”. Congruity effects in highly and less predictable sentence contexts

CONTEXT Using natural connected speech, the aim of the present study was to examine the semantic congruity effect (i.e. the difference between semantically incongruous and congruous words) in sentence contexts that generate high or moderate final word expectancies. METHODS We used sentences with two levels of word expectancy in the auditory modality: familiar proverbs (that generate high final word expectancy), and unfamiliar sentences (that generate only moderate final word expectancy). RESULTS Results revealed an early congruity effect (0-200 ms) that developed across all scalp sites for familiar proverbs but not for unfamiliar sentences. By contrast, typical centro-parietal N400 and Late Positivity Component congruity effects developed later (200-500 ms and 600-900 ms ranges) for both familiar proverbs and unfamiliar sentences. DISCUSSION We argue that the early congruity effect for proverbs comprises both a Phonological Mismatch Negativity, reflecting the processing of the acoustic/phonological mismatch between the expected (congruous) and unexpected (incongruous) sentence completions and a typical N400 semantic congruity effect with an unusual short latency because final words can be predicted from the unusually high contextual constraints of familiar proverbs. These results are considered in the light of current views of anticipation and prediction processes in sentence contexts.