Acoustic cues to deception on a picture-naming task were analyzed in three groups of English speakers: monolinguals, bilinguals with English as their first language, and bilinguals with English as a second language. Results revealed that all participants had longer reaction times when generating falsehoods than when producing truths, and that the effect was more robust for English as a second language bilinguals than for the other two groups. Articulation rate was higher for all groups when producing lies. Mean fundamental frequency and intensity cues were not reliable cues to deception, but there was lower variance in both of these parameters when generating false versus true labels for all participants. Results suggest that naming latency was the only cue to deception that differed by language background. These findings broadly support the cognitive-load theory of deception, suggesting that a combination of producing deceptive speech and using a second language puts an extra load on the speaker.

Speaking a late-acquired second language (L2) involves increased cognitive demands, as has been shown mainly in young and middle-aged adults. To investigate grammatical inflection in older L2 speakers, we acquired behavioral and functional magnetic resonance imaging data, while L1 and L2 speakers performed a grammaticality judgment task. L2 speakers showed higher error rates than native speakers, specifically when incorrect forms had to be rejected. Poorer performance in L2 speakers was accompanied by increased activity in the medial superior frontal gyrus (SFG), indicating the additional recruitment of executive control mechanisms. In addition, post-hoc within-group comparisons of behavioral and neural correlates provide evidence for dual-mechanism models in older adults, suggesting that language processing involves both procedural and declarative memory systems. Moreover, we demonstrated that speaking an L2 requires more executive control and relies to a lesser extent on the procedural memory system than speaking one's own native language.