Human information processing depends critically on continuous predictions about upcoming events, but the temporal convergence of expectancy-based top-down and input-driven bottom-up streams is poorly understood. We show that, during reading, event-related potentials differ between exposure to highly predictable and unpredictable words no later than 90 ms after visual input. This result suggests an extremely rapid comparison of expected and incoming visual information and gives an upper temporal bound for theories of top-down and bottom-up interactions in object recognition.

Morphological segmentation while reading is essential for new vocabulary learning. The study's aim was to investigate semantic-level morphological segmentation using event-related brain potentials (ERPs) in typical young adult readers. Past research has suggested that, because semantically opaque words prime their stems (e.g., corner/corn) similarly to transparent words (e.g., farmer/farm), readers recognize complex words from their constituent morphemes without regard to semantic information. However, this priming effect may be due to orthographic and phonological overlap between prime and target words. The research presented here addressed this possibility by creating five conditions in which orthographic, phonological, and semantic relationships between prime and target words were manipulated: Condition 1,wherein prime and target shared no relationship (e.g., inn/brother), served as Control. In Condition 2, prime and target were the same (e.g., brother/brother). In Condition 3, prime was the stem of target (e.g., broth/brother). Condition 4, our critical experimental condition, used primes semantically related to the stem of the target word (e.g., soup/brother). Finally, in Condition 5, prime was semantically related to the whole target word (e.g., sibling/brother). Semantically priming the stem (Condition 4) did not modulate the amplitude of the standard N400 ERP component (as did Conditions 2, 3, and 5), but did affect an early N400-like ERP component peaking in amplitude at ~262 ms after target. Other ERPs were observed that responded uniquely to shared orthography (Conditions 2, 3). Results set the stage for investigating morphological processing in adult reading impairments to evaluate whether, and to what extent, these readers semantically process morphological stems during text comprehension.