ERPs show that exemplar effects are driven by listeners' use of episodic memory
Annika Nijveld, Kimberley Mulder, Louis ten Bosch, Mirjam Ernestus · MPG.PuRe (Max Planck Society)
Listeners in priming experiments generally recognize repeated words more quickly and/or more accurately if repetitions share surface details (e.g., speaker voice) than if they do not. These exemplar effects, although not always replicated, suggest that word forms are stored as clouds of exemplars. These effects arose mostly when participants relied on their episodic memories (e.g., in old-new judgment tasks), suggesting that exemplar effects are driven by episodic memory (rather than the mental lexicon). However, some old-new judgment experiments did not obtain exemplar effects. Possibly, their method (behavioral responses) was not sensitive enough. We tested two hypotheses in two experiments: whether exemplar effects are driven by episodic memory, and whether they are better captured by EEG (electroencephalography). We repeated words in the same or a different voice (match and mismatch), and participants engaged in old-new (Experiment 1) or animacy judgment (Experiment 2; only the former task relying on episodic memory). We collected participants' behavioral responses and EEG. We predict larger exemplar effects Experiment 1 and in the ERP data (event-related potentials: stimulus-locked brain potentials derived from the EEG). In the ERPs, an N400 brain response peaked remarkably higher for the match than the mismatch condition in Experiment 1 only (an exemplar effect). Behaviorally, 'match' words received slightly more accurate responses in both experiments (no interaction arose). In response times, match and mismatch did not differ in either experiment (a null result). We thus only detected clear exemplar effects in our ERP data, indicating that exemplar effects which do not surface in behavior may still be present in cognitive processing (and can be measured with a more sensitive method like EEG). The effects only arose when participants had to use their episodic memories. This suggests that exemplar effects are driven by episodic memory rather than the mental lexicon.