But the study that caused the greatest interest was one which investigated verbs, comparing brain activation for regular past tense formations (e.g. jumped) with irregular ones (e.g. sang). The researchers found that irregular past tenses elicited a significantly greater amount of brain activity than the regular past tenses. This finding was no surprise to linguists, who had long ago concluded that past tenses of regular verbs are formed by the application of rules, but that irregular past tenses involve lexical memory.