How do individuals learn language when there are so many possible potential referents for each word? Prediction-basedtheories of language learning propose that predictions enable individuals to learn from implicit negative evidence bycomparing the predictions to outcomes. However, the role of prediction errors for learning has yet to be established.Traditionally, prediction errors have been believed to hinder learning. Recently though, prediction errors have been as-sociated with improved novel word acquisition in cross situational learning. This present study used a cross-situationalword learning task to examine the relation between prediction error-based processes during word learning and vocabularysize. The results showed that learners who switched their gaze more quickly from the non-target to the target image whenthey had to detect and correct prediction errors had higher productive vocabularies. This research supports the theory thatproductive vocabulary is strongly tied to predictive processes.

According to prediction-based theories, prior learning creates expectations for subsequent learning events. As they learn words, individuals develop accurate and inaccurate expectations about word meaning. Existing research shows that people who shift their gaze to the referent of words more quickly have larger vocabularies. This shifting reflects the processing of accurate expectations about the referents of these words. Is the speed of processing inaccurate expectations also related to vocabulary size? To examine this question, adults learned eight novel word-object mappings during cross-situational word learning (CSWL). The mappings were either consistent or inconsistent with a prior familiarization phase. Early in CSWL, hearing inconsistent words violated expectations about the referent of those words. Shifting from a distractor to the target of an inconsistent word during CSWL was significantly associated with productive and receptive vocabulary. These findings are consistent with prediction-based theories, in which individuals use prediction errors to adjust their expectations.

Adjusting expectations in response to errors is a cornerstone of several learning theories (Rescorla & Wagner, 1972; Rumelhart et al., 1986). Grimmick (2019) shows that individuals deploy attention during cross-situational word learning based on the strength of the error signal. The current study introduced an equal number of accurate and inaccurate expectations about word-referent pairs. This study manipulated the difficulty of cross-situational word learning trials to examine whether the impact of errors differs depending on task demands. Individuals learned the initially accurate items better than the initially inaccurate ones. Manipulating the demands during word learning did not significantly impact the tendency to benefit from accuracy. This research is part of an ongoing project. This ongoing research explores how individual differences in vocabulary, inhibition, and working memory abilities interact with contextual factors, such as task difficulty, as individuals learn word-referent pairs that violate their expectations.

Errors are usually viewed as detrimental to learning. Yet, recent proposals suggest that errors may create desirable difficul-ties and thereby improve learning. We evaluated these proposals in the context of cross-situational word learning. Duringeach learning trial, adults saw two images and heard two words. In the Error1 condition, the first word was unexpectedbased on prior experience and the second was expected. The referent of the unexpected word could only be establishedafter hearing the expected word. In the Error2 condition, the expected word came first, which made it easier to learn themapping of the subsequent unexpected word. There was no difference between the conditions; however, expected wordswere only learned significantly better than unexpected words in the Error2 condition. This suggests that the structure ofthe learning environment modulates the impact of errors.