Recognising individuals through their voice requires listeners to form an invariant representation of the speaker's identity, immune to episodic changes that may occur between encounters. We conducted two experiments to investigate to what extent within-speaker stimulus variability influences different behavioural indices of implicit and explicit identity recognition memory, using short sentences with semantically neutral content. In Experiment 1, we assessed how speaker recognition was affected by changes in prosody (fearful to neutral, and vice versa in a between-group design) and speech content. Results revealed that, regardless of encoding prosody, changes in prosody, independent of content, or changes in content, when prosody was kept unchanged, led to a reduced accuracy in explicit voice recognition. In contrast, both groups exhibited the same pattern of response times (RTs) for correctly recognised speakers: faster responses to fearful than neutral stimuli, and a facilitating effect for same-content stimuli only for neutral sentences. In Experiment 2, we investigated whether an invariant representation of a speaker's identity benefitted from exposure to different exemplars varying in emotional prosody (fearful and happy) and content (Multi condition), compared to repeated presentations of a single sentence (Uni condition). We found a significant repetition priming effect (i.e., reduced RTs over repetitions of the same voice identity) only for speakers in the Uni condition during encoding, but faster RTs when correctly recognising old speakers from the Multi, compared to the Uni, condition. Overall, our findings confirm that changes in emotional prosody and/or speech content can affect listeners' implicit and explicit recognition of newly familiarised speakers.
Keywords: Speaker recognition; emotional prosody; exemplar repetition.