To predict or not to predict: age-related differences in the use of sentential context

Older adults (as a group) are less likely than younger adults to engage in an anticipatory mode of language comprehension, failing to successfully preactivate information about upcoming likely (predictable) words during online processing. To assess (within one set of materials) age-related changes in the use of sentential context to affect processing of predictable words and in the consequences of violating predictions, event-related brain potentials were recorded while older adults read sentences that varied in sentence-level constraint and expectancy of sentence-final words. Strongly constraining sentences were completed by their most expected, predictable words and weakly constraining sentences were completed by their most expected, less predictable words. Both types of sentences also were completed by unexpected (but plausible) words. Older adults showed reduced and delayed effects of sentential context on processing predictable words. Whereas younger adults elicit an enhanced positive ERP (starting around 500 ms poststimulus onset, largest over prefrontal electrode sites), specifically for unexpected words that violate strong expectancies for a different word, older adults as a group did not exhibit this neural consequence of disconfirmed predictions. Older adults were instead more likely to show a left-lateralized frontal negativity for predictable items. This ERP response has been attributed to processes needed to revisit contextual material in forming an interpretation of message-level meaning, which may be more likely when anticipatory modes of comprehension are not engaged. Taken together, the results suggest that normal aging can affect allocation of resources to different cognitive and neural pathways in achieving comprehension outcomes.